video/fbdev/atmel_lcdfb.c

/*
 *  Driver for AT91 LCD Controller
 *
 *  Copyright (C) 2007 Atmel Corporation
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file COPYING in the main directory of this archive for
 * more details.
 */

#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/clk.h>
#include <linux/fb.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/backlight.h>
#include <linux/gfp.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <video/of_videomode.h>
#include <video/of_display_timing.h>
#include <linux/regulator/consumer.h>
#include <video/videomode.h>

#include <video/atmel_lcdc.h>

struct atmel_lcdfb_config {
	bool have_alt_pixclock;
	bool have_hozval;
	bool have_intensity_bit;
};

 /* LCD Controller info data structure, stored in device platform_data */
struct atmel_lcdfb_info {
	spinlock_t		lock;
	struct fb_info		*info;
	void __iomem		*mmio;
	int			irq_base;
	struct work_struct	task;

	unsigned int		smem_len;
	struct platform_device	*pdev;
	struct clk		*bus_clk;
	struct clk		*lcdc_clk;

	struct backlight_device	*backlight;
	u8			saved_lcdcon;

	u32			pseudo_palette[16];
	bool			have_intensity_bit;

	struct atmel_lcdfb_pdata pdata;

	struct atmel_lcdfb_config *config;
	struct regulator	*reg_lcd;
};

struct atmel_lcdfb_power_ctrl_gpio {
	struct gpio_desc *gpiod;

	struct list_head list;
};

#define lcdc_readl(sinfo, reg)		__raw_readl((sinfo)->mmio+(reg))
#define lcdc_writel(sinfo, reg, val)	__raw_writel((val), (sinfo)->mmio+(reg))

/* configurable parameters */
#define ATMEL_LCDC_CVAL_DEFAULT		0xc8
#define ATMEL_LCDC_DMA_BURST_LEN	8	/* words */
#define ATMEL_LCDC_FIFO_SIZE		512	/* words */

static struct atmel_lcdfb_config at91sam9261_config = {
	.have_hozval		= true,
	.have_intensity_bit	= true,
};

static struct atmel_lcdfb_config at91sam9263_config = {
	.have_intensity_bit	= true,
};

static struct atmel_lcdfb_config at91sam9g10_config = {
	.have_hozval		= true,
};

static struct atmel_lcdfb_config at91sam9g45_config = {
	.have_alt_pixclock	= true,
};

static struct atmel_lcdfb_config at91sam9g45es_config = {
};

static struct atmel_lcdfb_config at91sam9rl_config = {
	.have_intensity_bit	= true,
};

static u32 contrast_ctr = ATMEL_LCDC_PS_DIV8
		| ATMEL_LCDC_POL_POSITIVE
		| ATMEL_LCDC_ENA_PWMENABLE;

#ifdef CONFIG_BACKLIGHT_ATMEL_LCDC

/* some bl->props field just changed */
static int atmel_bl_update_status(struct backlight_device *bl)
{
	struct atmel_lcdfb_info *sinfo = bl_get_data(bl);
	int			brightness = backlight_get_brightness(bl);

	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_VAL, brightness);
	if (contrast_ctr & ATMEL_LCDC_POL_POSITIVE)
		lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR,
			brightness ? contrast_ctr : 0);
	else
		lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, contrast_ctr);

	return 0;
}

static int atmel_bl_get_brightness(struct backlight_device *bl)
{
	struct atmel_lcdfb_info *sinfo = bl_get_data(bl);

	return lcdc_readl(sinfo, ATMEL_LCDC_CONTRAST_VAL);
}

static const struct backlight_ops atmel_lcdc_bl_ops = {
	.update_status = atmel_bl_update_status,
	.get_brightness = atmel_bl_get_brightness,
};

static void init_backlight(struct atmel_lcdfb_info *sinfo)
{
	struct backlight_properties props;
	struct backlight_device	*bl;

	if (sinfo->backlight)
		return;

	memset(&props, 0, sizeof(struct backlight_properties));
	props.type = BACKLIGHT_RAW;
	props.max_brightness = 0xff;
	bl = backlight_device_register("backlight", &sinfo->pdev->dev, sinfo,
				       &atmel_lcdc_bl_ops, &props);
	if (IS_ERR(bl)) {
		dev_err(&sinfo->pdev->dev, "error %ld on backlight register\n",
				PTR_ERR(bl));
		return;
	}
	sinfo->backlight = bl;

	bl->props.power = FB_BLANK_UNBLANK;
	bl->props.fb_blank = FB_BLANK_UNBLANK;
	bl->props.brightness = atmel_bl_get_brightness(bl);
}

static void exit_backlight(struct atmel_lcdfb_info *sinfo)
{
	if (!sinfo->backlight)
		return;

	if (sinfo->backlight->ops) {
		sinfo->backlight->props.power = FB_BLANK_POWERDOWN;
		sinfo->backlight->ops->update_status(sinfo->backlight);
	}
	backlight_device_unregister(sinfo->backlight);
}

#else

static void init_backlight(struct atmel_lcdfb_info *sinfo)
{
	dev_warn(&sinfo->pdev->dev, "backlight control is not available\n");
}

static void exit_backlight(struct atmel_lcdfb_info *sinfo)
{
}

#endif

static void init_contrast(struct atmel_lcdfb_info *sinfo)
{
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;

	/* contrast pwm can be 'inverted' */
	if (pdata->lcdcon_pol_negative)
		contrast_ctr &= ~(ATMEL_LCDC_POL_POSITIVE);

	/* have some default contrast/backlight settings */
	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, contrast_ctr);
	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_VAL, ATMEL_LCDC_CVAL_DEFAULT);

	if (pdata->lcdcon_is_backlight)
		init_backlight(sinfo);
}

static inline void atmel_lcdfb_power_control(struct atmel_lcdfb_info *sinfo, int on)
{
	int ret;
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;

	if (pdata->atmel_lcdfb_power_control)
		pdata->atmel_lcdfb_power_control(pdata, on);
	else if (sinfo->reg_lcd) {
		if (on) {
			ret = regulator_enable(sinfo->reg_lcd);
			if (ret)
				dev_err(&sinfo->pdev->dev,
					"lcd regulator enable failed:	%d\n", ret);
		} else {
			ret = regulator_disable(sinfo->reg_lcd);
			if (ret)
				dev_err(&sinfo->pdev->dev,
					"lcd regulator disable failed: %d\n", ret);
		}
	}
}

static const struct fb_fix_screeninfo atmel_lcdfb_fix __initconst = {
	.type		= FB_TYPE_PACKED_PIXELS,
	.visual		= FB_VISUAL_TRUECOLOR,
	.xpanstep	= 0,
	.ypanstep	= 1,
	.ywrapstep	= 0,
	.accel		= FB_ACCEL_NONE,
};

static unsigned long compute_hozval(struct atmel_lcdfb_info *sinfo,
							unsigned long xres)
{
	unsigned long lcdcon2;
	unsigned long value;

	if (!sinfo->config->have_hozval)
		return xres;

	lcdcon2 = lcdc_readl(sinfo, ATMEL_LCDC_LCDCON2);
	value = xres;
	if ((lcdcon2 & ATMEL_LCDC_DISTYPE) != ATMEL_LCDC_DISTYPE_TFT) {
		/* STN display */
		if ((lcdcon2 & ATMEL_LCDC_DISTYPE) == ATMEL_LCDC_DISTYPE_STNCOLOR) {
			value *= 3;
		}
		if ( (lcdcon2 & ATMEL_LCDC_IFWIDTH) == ATMEL_LCDC_IFWIDTH_4
		   || ( (lcdcon2 & ATMEL_LCDC_IFWIDTH) == ATMEL_LCDC_IFWIDTH_8
		      && (lcdcon2 & ATMEL_LCDC_SCANMOD) == ATMEL_LCDC_SCANMOD_DUAL ))
			value = DIV_ROUND_UP(value, 4);
		else
			value = DIV_ROUND_UP(value, 8);
	}

	return value;
}

static void atmel_lcdfb_stop_nowait(struct atmel_lcdfb_info *sinfo)
{
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;

	/* Turn off the LCD controller and the DMA controller */
	lcdc_writel(sinfo, ATMEL_LCDC_PWRCON,
			pdata->guard_time << ATMEL_LCDC_GUARDT_OFFSET);

	/* Wait for the LCDC core to become idle */
	while (lcdc_readl(sinfo, ATMEL_LCDC_PWRCON) & ATMEL_LCDC_BUSY)
		msleep(10);

	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, 0);
}

static void atmel_lcdfb_stop(struct atmel_lcdfb_info *sinfo)
{
	atmel_lcdfb_stop_nowait(sinfo);

	/* Wait for DMA engine to become idle... */
	while (lcdc_readl(sinfo, ATMEL_LCDC_DMACON) & ATMEL_LCDC_DMABUSY)
		msleep(10);
}

static void atmel_lcdfb_start(struct atmel_lcdfb_info *sinfo)
{
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;

	lcdc_writel(sinfo, ATMEL_LCDC_DMACON, pdata->default_dmacon);
	lcdc_writel(sinfo, ATMEL_LCDC_PWRCON,
		(pdata->guard_time << ATMEL_LCDC_GUARDT_OFFSET)
		| ATMEL_LCDC_PWR);
}

static void atmel_lcdfb_update_dma(struct fb_info *info,
			       struct fb_var_screeninfo *var)
{
	struct atmel_lcdfb_info *sinfo = info->par;
	struct fb_fix_screeninfo *fix = &info->fix;
	unsigned long dma_addr;

	dma_addr = (fix->smem_start + var->yoffset * fix->line_length
		    + var->xoffset * info->var.bits_per_pixel / 8);

	dma_addr &= ~3UL;

	/* Set framebuffer DMA base address and pixel offset */
	lcdc_writel(sinfo, ATMEL_LCDC_DMABADDR1, dma_addr);
}

static inline void atmel_lcdfb_free_video_memory(struct atmel_lcdfb_info *sinfo)
{
	struct fb_info *info = sinfo->info;

	dma_free_wc(info->device, info->fix.smem_len, info->screen_base,
		    info->fix.smem_start);
}

/**
 *	atmel_lcdfb_alloc_video_memory - Allocate framebuffer memory
 *	@sinfo: the frame buffer to allocate memory for
 *
 * 	This function is called only from the atmel_lcdfb_probe()
 * 	so no locking by fb_info->mm_lock around smem_len setting is needed.
 */
static int atmel_lcdfb_alloc_video_memory(struct atmel_lcdfb_info *sinfo)
{
	struct fb_info *info = sinfo->info;
	struct fb_var_screeninfo *var = &info->var;
	unsigned int smem_len;

	smem_len = (var->xres_virtual * var->yres_virtual
		    * ((var->bits_per_pixel + 7) / 8));
	info->fix.smem_len = max(smem_len, sinfo->smem_len);

	info->screen_base = dma_alloc_wc(info->device, info->fix.smem_len,
					 (dma_addr_t *)&info->fix.smem_start,
					 GFP_KERNEL);

	if (!info->screen_base) {
		return -ENOMEM;
	}

	memset(info->screen_base, 0, info->fix.smem_len);

	return 0;
}

static const struct fb_videomode *atmel_lcdfb_choose_mode(struct fb_var_screeninfo *var,
						     struct fb_info *info)
{
	struct fb_videomode varfbmode;
	const struct fb_videomode *fbmode = NULL;

	fb_var_to_videomode(&varfbmode, var);
	fbmode = fb_find_nearest_mode(&varfbmode, &info->modelist);
	if (fbmode)
		fb_videomode_to_var(var, fbmode);
	return fbmode;
}


/**
 *      atmel_lcdfb_check_var - Validates a var passed in.
 *      @var: frame buffer variable screen structure
 *      @info: frame buffer structure that represents a single frame buffer
 *
 *	Checks to see if the hardware supports the state requested by
 *	var passed in. This function does not alter the hardware
 *	state!!!  This means the data stored in struct fb_info and
 *	struct atmel_lcdfb_info do not change. This includes the var
 *	inside of struct fb_info.  Do NOT change these. This function
 *	can be called on its own if we intent to only test a mode and
 *	not actually set it. The stuff in modedb.c is a example of
 *	this. If the var passed in is slightly off by what the
 *	hardware can support then we alter the var PASSED in to what
 *	we can do. If the hardware doesn't support mode change a
 *	-EINVAL will be returned by the upper layers. You don't need
 *	to implement this function then. If you hardware doesn't
 *	support changing the resolution then this function is not
 *	needed. In this case the driver would just provide a var that
 *	represents the static state the screen is in.
 *
 *	Returns negative errno on error, or zero on success.
 */
static int atmel_lcdfb_check_var(struct fb_var_screeninfo *var,
			     struct fb_info *info)
{
	struct device *dev = info->device;
	struct atmel_lcdfb_info *sinfo = info->par;
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;
	unsigned long clk_value_khz;

	clk_value_khz = clk_get_rate(sinfo->lcdc_clk) / 1000;

	dev_dbg(dev, "%s:\n", __func__);

	if (!(var->pixclock && var->bits_per_pixel)) {
		/* choose a suitable mode if possible */
		if (!atmel_lcdfb_choose_mode(var, info)) {
			dev_err(dev, "needed value not specified\n");
			return -EINVAL;
		}
	}

	dev_dbg(dev, "  resolution: %ux%u\n", var->xres, var->yres);
	dev_dbg(dev, "  pixclk:     %lu KHz\n", PICOS2KHZ(var->pixclock));
	dev_dbg(dev, "  bpp:        %u\n", var->bits_per_pixel);
	dev_dbg(dev, "  clk:        %lu KHz\n", clk_value_khz);

	if (PICOS2KHZ(var->pixclock) > clk_value_khz) {
		dev_err(dev, "%lu KHz pixel clock is too fast\n", PICOS2KHZ(var->pixclock));
		return -EINVAL;
	}

	/* Do not allow to have real resoulution larger than virtual */
	if (var->xres > var->xres_virtual)
		var->xres_virtual = var->xres;

	if (var->yres > var->yres_virtual)
		var->yres_virtual = var->yres;

	/* Force same alignment for each line */
	var->xres = (var->xres + 3) & ~3UL;
	var->xres_virtual = (var->xres_virtual + 3) & ~3UL;

	var->red.msb_right = var->green.msb_right = var->blue.msb_right = 0;
	var->transp.msb_right = 0;
	var->transp.offset = var->transp.length = 0;
	var->xoffset = var->yoffset = 0;

	if (info->fix.smem_len) {
		unsigned int smem_len = (var->xres_virtual * var->yres_virtual
					 * ((var->bits_per_pixel + 7) / 8));
		if (smem_len > info->fix.smem_len) {
			dev_err(dev, "Frame buffer is too small (%u) for screen size (need at least %u)\n",
				info->fix.smem_len, smem_len);
			return -EINVAL;
		}
	}

	/* Saturate vertical and horizontal timings at maximum values */
	var->vsync_len = min_t(u32, var->vsync_len,
			(ATMEL_LCDC_VPW >> ATMEL_LCDC_VPW_OFFSET) + 1);
	var->upper_margin = min_t(u32, var->upper_margin,
			ATMEL_LCDC_VBP >> ATMEL_LCDC_VBP_OFFSET);
	var->lower_margin = min_t(u32, var->lower_margin,
			ATMEL_LCDC_VFP);
	var->right_margin = min_t(u32, var->right_margin,
			(ATMEL_LCDC_HFP >> ATMEL_LCDC_HFP_OFFSET) + 1);
	var->hsync_len = min_t(u32, var->hsync_len,
			(ATMEL_LCDC_HPW >> ATMEL_LCDC_HPW_OFFSET) + 1);
	var->left_margin = min_t(u32, var->left_margin,
			ATMEL_LCDC_HBP + 1);

	/* Some parameters can't be zero */
	var->vsync_len = max_t(u32, var->vsync_len, 1);
	var->right_margin = max_t(u32, var->right_margin, 1);
	var->hsync_len = max_t(u32, var->hsync_len, 1);
	var->left_margin = max_t(u32, var->left_margin, 1);

	switch (var->bits_per_pixel) {
	case 1:
	case 2:
	case 4:
	case 8:
		var->red.offset = var->green.offset = var->blue.offset = 0;
		var->red.length = var->green.length = var->blue.length
			= var->bits_per_pixel;
		break;
	case 16:
		/* Older SOCs use IBGR:555 rather than BGR:565. */
		if (sinfo->config->have_intensity_bit)
			var->green.length = 5;
		else
			var->green.length = 6;

		if (pdata->lcd_wiring_mode == ATMEL_LCDC_WIRING_RGB) {
			/* RGB:5X5 mode */
			var->red.offset = var->green.length + 5;
			var->blue.offset = 0;
		} else {
			/* BGR:5X5 mode */
			var->red.offset = 0;
			var->blue.offset = var->green.length + 5;
		}
		var->green.offset = 5;
		var->red.length = var->blue.length = 5;
		break;
	case 32:
		var->transp.offset = 24;
		var->transp.length = 8;
		fallthrough;
	case 24:
		if (pdata->lcd_wiring_mode == ATMEL_LCDC_WIRING_RGB) {
			/* RGB:888 mode */
			var->red.offset = 16;
			var->blue.offset = 0;
		} else {
			/* BGR:888 mode */
			var->red.offset = 0;
			var->blue.offset = 16;
		}
		var->green.offset = 8;
		var->red.length = var->green.length = var->blue.length = 8;
		break;
	default:
		dev_err(dev, "color depth %d not supported\n",
					var->bits_per_pixel);
		return -EINVAL;
	}

	return 0;
}

/*
 * LCD reset sequence
 */
static void atmel_lcdfb_reset(struct atmel_lcdfb_info *sinfo)
{
	might_sleep();

	atmel_lcdfb_stop(sinfo);
	atmel_lcdfb_start(sinfo);
}

/**
 *      atmel_lcdfb_set_par - Alters the hardware state.
 *      @info: frame buffer structure that represents a single frame buffer
 *
 *	Using the fb_var_screeninfo in fb_info we set the resolution
 *	of the this particular framebuffer. This function alters the
 *	par AND the fb_fix_screeninfo stored in fb_info. It doesn't
 *	not alter var in fb_info since we are using that data. This
 *	means we depend on the data in var inside fb_info to be
 *	supported by the hardware.  atmel_lcdfb_check_var is always called
 *	before atmel_lcdfb_set_par to ensure this.  Again if you can't
 *	change the resolution you don't need this function.
 *
 */
static int atmel_lcdfb_set_par(struct fb_info *info)
{
	struct atmel_lcdfb_info *sinfo = info->par;
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;
	unsigned long hozval_linesz;
	unsigned long value;
	unsigned long clk_value_khz;
	unsigned long bits_per_line;
	unsigned long pix_factor = 2;

	might_sleep();

	dev_dbg(info->device, "%s:\n", __func__);
	dev_dbg(info->device, "  * resolution: %ux%u (%ux%u virtual)\n",
		 info->var.xres, info->var.yres,
		 info->var.xres_virtual, info->var.yres_virtual);

	atmel_lcdfb_stop_nowait(sinfo);

	if (info->var.bits_per_pixel == 1)
		info->fix.visual = FB_VISUAL_MONO01;
	else if (info->var.bits_per_pixel <= 8)
		info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
	else
		info->fix.visual = FB_VISUAL_TRUECOLOR;

	bits_per_line = info->var.xres_virtual * info->var.bits_per_pixel;
	info->fix.line_length = DIV_ROUND_UP(bits_per_line, 8);

	/* Re-initialize the DMA engine... */
	dev_dbg(info->device, "  * update DMA engine\n");
	atmel_lcdfb_update_dma(info, &info->var);

	/* ...set frame size and burst length = 8 words (?) */
	value = (info->var.yres * info->var.xres * info->var.bits_per_pixel) / 32;
	value |= ((ATMEL_LCDC_DMA_BURST_LEN - 1) << ATMEL_LCDC_BLENGTH_OFFSET);
	lcdc_writel(sinfo, ATMEL_LCDC_DMAFRMCFG, value);

	/* Now, the LCDC core... */

	/* Set pixel clock */
	if (sinfo->config->have_alt_pixclock)
		pix_factor = 1;

	clk_value_khz = clk_get_rate(sinfo->lcdc_clk) / 1000;

	value = DIV_ROUND_UP(clk_value_khz, PICOS2KHZ(info->var.pixclock));

	if (value < pix_factor) {
		dev_notice(info->device, "Bypassing pixel clock divider\n");
		lcdc_writel(sinfo, ATMEL_LCDC_LCDCON1, ATMEL_LCDC_BYPASS);
	} else {
		value = (value / pix_factor) - 1;
		dev_dbg(info->device, "  * programming CLKVAL = 0x%08lx\n",
				value);
		lcdc_writel(sinfo, ATMEL_LCDC_LCDCON1,
				value << ATMEL_LCDC_CLKVAL_OFFSET);
		info->var.pixclock =
			KHZ2PICOS(clk_value_khz / (pix_factor * (value + 1)));
		dev_dbg(info->device, "  updated pixclk:     %lu KHz\n",
					PICOS2KHZ(info->var.pixclock));
	}


	/* Initialize control register 2 */
	value = pdata->default_lcdcon2;

	if (!(info->var.sync & FB_SYNC_HOR_HIGH_ACT))
		value |= ATMEL_LCDC_INVLINE_INVERTED;
	if (!(info->var.sync & FB_SYNC_VERT_HIGH_ACT))
		value |= ATMEL_LCDC_INVFRAME_INVERTED;

	switch (info->var.bits_per_pixel) {
		case 1:	value |= ATMEL_LCDC_PIXELSIZE_1; break;
		case 2: value |= ATMEL_LCDC_PIXELSIZE_2; break;
		case 4: value |= ATMEL_LCDC_PIXELSIZE_4; break;
		case 8: value |= ATMEL_LCDC_PIXELSIZE_8; break;
		case 15: fallthrough;
		case 16: value |= ATMEL_LCDC_PIXELSIZE_16; break;
		case 24: value |= ATMEL_LCDC_PIXELSIZE_24; break;
		case 32: value |= ATMEL_LCDC_PIXELSIZE_32; break;
		default: BUG(); break;
	}
	dev_dbg(info->device, "  * LCDCON2 = %08lx\n", value);
	lcdc_writel(sinfo, ATMEL_LCDC_LCDCON2, value);

	/* Vertical timing */
	value = (info->var.vsync_len - 1) << ATMEL_LCDC_VPW_OFFSET;
	value |= info->var.upper_margin << ATMEL_LCDC_VBP_OFFSET;
	value |= info->var.lower_margin;
	dev_dbg(info->device, "  * LCDTIM1 = %08lx\n", value);
	lcdc_writel(sinfo, ATMEL_LCDC_TIM1, value);

	/* Horizontal timing */
	value = (info->var.right_margin - 1) << ATMEL_LCDC_HFP_OFFSET;
	value |= (info->var.hsync_len - 1) << ATMEL_LCDC_HPW_OFFSET;
	value |= (info->var.left_margin - 1);
	dev_dbg(info->device, "  * LCDTIM2 = %08lx\n", value);
	lcdc_writel(sinfo, ATMEL_LCDC_TIM2, value);

	/* Horizontal value (aka line size) */
	hozval_linesz = compute_hozval(sinfo, info->var.xres);

	/* Display size */
	value = (hozval_linesz - 1) << ATMEL_LCDC_HOZVAL_OFFSET;
	value |= info->var.yres - 1;
	dev_dbg(info->device, "  * LCDFRMCFG = %08lx\n", value);
	lcdc_writel(sinfo, ATMEL_LCDC_LCDFRMCFG, value);

	/* FIFO Threshold: Use formula from data sheet */
	value = ATMEL_LCDC_FIFO_SIZE - (2 * ATMEL_LCDC_DMA_BURST_LEN + 3);
	lcdc_writel(sinfo, ATMEL_LCDC_FIFO, value);

	/* Toggle LCD_MODE every frame */
	lcdc_writel(sinfo, ATMEL_LCDC_MVAL, 0);

	/* Disable all interrupts */
	lcdc_writel(sinfo, ATMEL_LCDC_IDR, ~0U);
	/* Enable FIFO & DMA errors */
	lcdc_writel(sinfo, ATMEL_LCDC_IER, ATMEL_LCDC_UFLWI | ATMEL_LCDC_OWRI | ATMEL_LCDC_MERI);

	/* ...wait for DMA engine to become idle... */
	while (lcdc_readl(sinfo, ATMEL_LCDC_DMACON) & ATMEL_LCDC_DMABUSY)
		msleep(10);

	atmel_lcdfb_start(sinfo);

	dev_dbg(info->device, "  * DONE\n");

	return 0;
}

static inline unsigned int chan_to_field(unsigned int chan, const struct fb_bitfield *bf)
{
	chan &= 0xffff;
	chan >>= 16 - bf->length;
	return chan << bf->offset;
}

/**
 *  	atmel_lcdfb_setcolreg - Optional function. Sets a color register.
 *      @regno: Which register in the CLUT we are programming
 *      @red: The red value which can be up to 16 bits wide
 *	@green: The green value which can be up to 16 bits wide
 *	@blue:  The blue value which can be up to 16 bits wide.
 *	@transp: If supported the alpha value which can be up to 16 bits wide.
 *      @info: frame buffer info structure
 *
 *  	Set a single color register. The values supplied have a 16 bit
 *  	magnitude which needs to be scaled in this function for the hardware.
 *	Things to take into consideration are how many color registers, if
 *	any, are supported with the current color visual. With truecolor mode
 *	no color palettes are supported. Here a pseudo palette is created
 *	which we store the value in pseudo_palette in struct fb_info. For
 *	pseudocolor mode we have a limited color palette. To deal with this
 *	we can program what color is displayed for a particular pixel value.
 *	DirectColor is similar in that we can program each color field. If
 *	we have a static colormap we don't need to implement this function.
 *
 *	Returns negative errno on error, or zero on success. In an
 *	ideal world, this would have been the case, but as it turns
 *	out, the other drivers return 1 on failure, so that's what
 *	we're going to do.
 */
static int atmel_lcdfb_setcolreg(unsigned int regno, unsigned int red,
			     unsigned int green, unsigned int blue,
			     unsigned int transp, struct fb_info *info)
{
	struct atmel_lcdfb_info *sinfo = info->par;
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;
	unsigned int val;
	u32 *pal;
	int ret = 1;

	if (info->var.grayscale)
		red = green = blue = (19595 * red + 38470 * green
				      + 7471 * blue) >> 16;

	switch (info->fix.visual) {
	case FB_VISUAL_TRUECOLOR:
		if (regno < 16) {
			pal = info->pseudo_palette;

			val  = chan_to_field(red, &info->var.red);
			val |= chan_to_field(green, &info->var.green);
			val |= chan_to_field(blue, &info->var.blue);

			pal[regno] = val;
			ret = 0;
		}
		break;

	case FB_VISUAL_PSEUDOCOLOR:
		if (regno < 256) {
			if (sinfo->config->have_intensity_bit) {
				/* old style I+BGR:555 */
				val  = ((red   >> 11) & 0x001f);
				val |= ((green >>  6) & 0x03e0);
				val |= ((blue  >>  1) & 0x7c00);

				/*
				 * TODO: intensity bit. Maybe something like
				 *   ~(red[10] ^ green[10] ^ blue[10]) & 1
				 */
			} else {
				/* new style BGR:565 / RGB:565 */
				if (pdata->lcd_wiring_mode == ATMEL_LCDC_WIRING_RGB) {
					val  = ((blue >> 11) & 0x001f);
					val |= ((red  >>  0) & 0xf800);
				} else {
					val  = ((red  >> 11) & 0x001f);
					val |= ((blue >>  0) & 0xf800);
				}

				val |= ((green >>  5) & 0x07e0);
			}

			lcdc_writel(sinfo, ATMEL_LCDC_LUT(regno), val);
			ret = 0;
		}
		break;

	case FB_VISUAL_MONO01:
		if (regno < 2) {
			val = (regno == 0) ? 0x00 : 0x1F;
			lcdc_writel(sinfo, ATMEL_LCDC_LUT(regno), val);
			ret = 0;
		}
		break;

	}

	return ret;
}

static int atmel_lcdfb_pan_display(struct fb_var_screeninfo *var,
			       struct fb_info *info)
{
	dev_dbg(info->device, "%s\n", __func__);

	atmel_lcdfb_update_dma(info, var);

	return 0;
}

static int atmel_lcdfb_blank(int blank_mode, struct fb_info *info)
{
	struct atmel_lcdfb_info *sinfo = info->par;

	switch (blank_mode) {
	case FB_BLANK_UNBLANK:
	case FB_BLANK_NORMAL:
		atmel_lcdfb_start(sinfo);
		break;
	case FB_BLANK_VSYNC_SUSPEND:
	case FB_BLANK_HSYNC_SUSPEND:
		break;
	case FB_BLANK_POWERDOWN:
		atmel_lcdfb_stop(sinfo);
		break;
	default:
		return -EINVAL;
	}

	/* let fbcon do a soft blank for us */
	return ((blank_mode == FB_BLANK_NORMAL) ? 1 : 0);
}

static const struct fb_ops atmel_lcdfb_ops = {
	.owner		= THIS_MODULE,
	FB_DEFAULT_IOMEM_OPS,
	.fb_check_var	= atmel_lcdfb_check_var,
	.fb_set_par	= atmel_lcdfb_set_par,
	.fb_setcolreg	= atmel_lcdfb_setcolreg,
	.fb_blank	= atmel_lcdfb_blank,
	.fb_pan_display	= atmel_lcdfb_pan_display,
};

static irqreturn_t atmel_lcdfb_interrupt(int irq, void *dev_id)
{
	struct fb_info *info = dev_id;
	struct atmel_lcdfb_info *sinfo = info->par;
	u32 status;

	status = lcdc_readl(sinfo, ATMEL_LCDC_ISR);
	if (status & ATMEL_LCDC_UFLWI) {
		dev_warn(info->device, "FIFO underflow %#x\n", status);
		/* reset DMA and FIFO to avoid screen shifting */
		schedule_work(&sinfo->task);
	}
	lcdc_writel(sinfo, ATMEL_LCDC_ICR, status);
	return IRQ_HANDLED;
}

/*
 * LCD controller task (to reset the LCD)
 */
static void atmel_lcdfb_task(struct work_struct *work)
{
	struct atmel_lcdfb_info *sinfo =
		container_of(work, struct atmel_lcdfb_info, task);

	atmel_lcdfb_reset(sinfo);
}

static int __init atmel_lcdfb_init_fbinfo(struct atmel_lcdfb_info *sinfo)
{
	struct fb_info *info = sinfo->info;
	int ret = 0;

	info->var.activate |= FB_ACTIVATE_FORCE | FB_ACTIVATE_NOW;

	dev_info(info->device,
	       "%luKiB frame buffer at %08lx (mapped at %p)\n",
	       (unsigned long)info->fix.smem_len / 1024,
	       (unsigned long)info->fix.smem_start,
	       info->screen_base);

	/* Allocate colormap */
	ret = fb_alloc_cmap(&info->cmap, 256, 0);
	if (ret < 0)
		dev_err(info->device, "Alloc color map failed\n");

	return ret;
}

static void atmel_lcdfb_start_clock(struct atmel_lcdfb_info *sinfo)
{
	clk_prepare_enable(sinfo->bus_clk);
	clk_prepare_enable(sinfo->lcdc_clk);
}

static void atmel_lcdfb_stop_clock(struct atmel_lcdfb_info *sinfo)
{
	clk_disable_unprepare(sinfo->bus_clk);
	clk_disable_unprepare(sinfo->lcdc_clk);
}

static const struct of_device_id atmel_lcdfb_dt_ids[] = {
	{ .compatible = "atmel,at91sam9261-lcdc" , .data = &at91sam9261_config, },
	{ .compatible = "atmel,at91sam9263-lcdc" , .data = &at91sam9263_config, },
	{ .compatible = "atmel,at91sam9g10-lcdc" , .data = &at91sam9g10_config, },
	{ .compatible = "atmel,at91sam9g45-lcdc" , .data = &at91sam9g45_config, },
	{ .compatible = "atmel,at91sam9g45es-lcdc" , .data = &at91sam9g45es_config, },
	{ .compatible = "atmel,at91sam9rl-lcdc" , .data = &at91sam9rl_config, },
	{ /* sentinel */ }
};

MODULE_DEVICE_TABLE(of, atmel_lcdfb_dt_ids);

static const char *atmel_lcdfb_wiring_modes[] = {
	[ATMEL_LCDC_WIRING_BGR]	= "BRG",
	[ATMEL_LCDC_WIRING_RGB]	= "RGB",
};

static int atmel_lcdfb_get_of_wiring_modes(struct device_node *np)
{
	const char *mode;
	int err, i;

	err = of_property_read_string(np, "atmel,lcd-wiring-mode", &mode);
	if (err < 0)
		return ATMEL_LCDC_WIRING_BGR;

	for (i = 0; i < ARRAY_SIZE(atmel_lcdfb_wiring_modes); i++)
		if (!strcasecmp(mode, atmel_lcdfb_wiring_modes[i]))
			return i;

	return -ENODEV;
}

static void atmel_lcdfb_power_control_gpio(struct atmel_lcdfb_pdata *pdata, int on)
{
	struct atmel_lcdfb_power_ctrl_gpio *og;

	list_for_each_entry(og, &pdata->pwr_gpios, list)
		gpiod_set_value(og->gpiod, on);
}

static int atmel_lcdfb_of_init(struct atmel_lcdfb_info *sinfo)
{
	struct fb_info *info = sinfo->info;
	struct atmel_lcdfb_pdata *pdata = &sinfo->pdata;
	struct fb_var_screeninfo *var = &info->var;
	struct device *dev = &sinfo->pdev->dev;
	struct device_node *np =dev->of_node;
	struct device_node *display_np;
	struct atmel_lcdfb_power_ctrl_gpio *og;
	bool is_gpio_power = false;
	struct fb_videomode fb_vm;
	struct gpio_desc *gpiod;
	struct videomode vm;
	int ret;
	int i;

	sinfo->config = (struct atmel_lcdfb_config*)
		of_match_device(atmel_lcdfb_dt_ids, dev)->data;

	display_np = of_parse_phandle(np, "display", 0);
	if (!display_np) {
		dev_err(dev, "failed to find display phandle\n");
		return -ENOENT;
	}

	ret = of_property_read_u32(display_np, "bits-per-pixel", &var->bits_per_pixel);
	if (ret < 0) {
		dev_err(dev, "failed to get property bits-per-pixel\n");
		goto put_display_node;
	}

	ret = of_property_read_u32(display_np, "atmel,guard-time", &pdata->guard_time);
	if (ret < 0) {
		dev_err(dev, "failed to get property atmel,guard-time\n");
		goto put_display_node;
	}

	ret = of_property_read_u32(display_np, "atmel,lcdcon2", &pdata->default_lcdcon2);
	if (ret < 0) {
		dev_err(dev, "failed to get property atmel,lcdcon2\n");
		goto put_display_node;
	}

	ret = of_property_read_u32(display_np, "atmel,dmacon", &pdata->default_dmacon);
	if (ret < 0) {
		dev_err(dev, "failed to get property bits-per-pixel\n");
		goto put_display_node;
	}

	INIT_LIST_HEAD(&pdata->pwr_gpios);
	for (i = 0; i < gpiod_count(dev, "atmel,power-control"); i++) {
		ret = -ENOMEM;
		gpiod = devm_gpiod_get_index(dev, "atmel,power-control",
					     i, GPIOD_ASIS);
		if (IS_ERR(gpiod))
			continue;

		og = devm_kzalloc(dev, sizeof(*og), GFP_KERNEL);
		if (!og)
			goto put_display_node;

		og->gpiod = gpiod;
		is_gpio_power = true;

		ret = gpiod_direction_output(gpiod, gpiod_is_active_low(gpiod));
		if (ret) {
			dev_err(dev, "set direction output gpio atmel,power-control[%d] failed\n", i);
			goto put_display_node;
		}
		list_add(&og->list, &pdata->pwr_gpios);
	}

	if (is_gpio_power)
		pdata->atmel_lcdfb_power_control = atmel_lcdfb_power_control_gpio;

	ret = atmel_lcdfb_get_of_wiring_modes(display_np);
	if (ret < 0) {
		dev_err(dev, "invalid atmel,lcd-wiring-mode\n");
		goto put_display_node;
	}
	pdata->lcd_wiring_mode = ret;

	pdata->lcdcon_is_backlight = of_property_read_bool(display_np, "atmel,lcdcon-backlight");
	pdata->lcdcon_pol_negative = of_property_read_bool(display_np, "atmel,lcdcon-backlight-inverted");

	ret = of_get_videomode(display_np, &vm, OF_USE_NATIVE_MODE);
	if (ret) {
		dev_err(dev, "failed to get videomode from DT\n");
		goto put_display_node;
	}

	ret = fb_videomode_from_videomode(&vm, &fb_vm);
	if (ret < 0)
		goto put_display_node;

	fb_add_videomode(&fb_vm, &info->modelist);

put_display_node:
	of_node_put(display_np);
	return ret;
}

static int __init atmel_lcdfb_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct fb_info *info;
	struct atmel_lcdfb_info *sinfo;
	struct resource *regs = NULL;
	struct resource *map = NULL;
	struct fb_modelist *modelist;
	int ret;

	dev_dbg(dev, "%s BEGIN\n", __func__);

	ret = -ENOMEM;
	info = framebuffer_alloc(sizeof(struct atmel_lcdfb_info), dev);
	if (!info)
		goto out;

	sinfo = info->par;
	sinfo->pdev = pdev;
	sinfo->info = info;

	INIT_LIST_HEAD(&info->modelist);

	if (!pdev->dev.of_node) {
		dev_err(dev, "cannot get default configuration\n");
		goto free_info;
	}

	ret = atmel_lcdfb_of_init(sinfo);
	if (ret)
		goto free_info;

	ret = -ENODEV;
	if (!sinfo->config)
		goto free_info;

	sinfo->reg_lcd = devm_regulator_get(&pdev->dev, "lcd");
	if (IS_ERR(sinfo->reg_lcd))
		sinfo->reg_lcd = NULL;

	info->flags = FBINFO_PARTIAL_PAN_OK |
		      FBINFO_HWACCEL_YPAN;
	info->pseudo_palette = sinfo->pseudo_palette;
	info->fbops = &atmel_lcdfb_ops;

	info->fix = atmel_lcdfb_fix;
	strcpy(info->fix.id, sinfo->pdev->name);

	/* Enable LCDC Clocks */
	sinfo->bus_clk = clk_get(dev, "hclk");
	if (IS_ERR(sinfo->bus_clk)) {
		ret = PTR_ERR(sinfo->bus_clk);
		goto free_info;
	}
	sinfo->lcdc_clk = clk_get(dev, "lcdc_clk");
	if (IS_ERR(sinfo->lcdc_clk)) {
		ret = PTR_ERR(sinfo->lcdc_clk);
		goto put_bus_clk;
	}
	atmel_lcdfb_start_clock(sinfo);

	modelist = list_first_entry(&info->modelist,
			struct fb_modelist, list);
	fb_videomode_to_var(&info->var, &modelist->mode);

	atmel_lcdfb_check_var(&info->var, info);

	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!regs) {
		dev_err(dev, "resources unusable\n");
		ret = -ENXIO;
		goto stop_clk;
	}

	sinfo->irq_base = platform_get_irq(pdev, 0);
	if (sinfo->irq_base < 0) {
		ret = sinfo->irq_base;
		goto stop_clk;
	}

	/* Initialize video memory */
	map = platform_get_resource(pdev, IORESOURCE_MEM, 1);
	if (map) {
		/* use a pre-allocated memory buffer */
		info->fix.smem_start = map->start;
		info->fix.smem_len = resource_size(map);
		if (!request_mem_region(info->fix.smem_start,
					info->fix.smem_len, pdev->name)) {
			ret = -EBUSY;
			goto stop_clk;
		}

		info->screen_base = ioremap_wc(info->fix.smem_start,
					       info->fix.smem_len);
		if (!info->screen_base) {
			ret = -ENOMEM;
			goto release_intmem;
		}

		/*
		 * Don't clear the framebuffer -- someone may have set
		 * up a splash image.
		 */
	} else {
		/* allocate memory buffer */
		ret = atmel_lcdfb_alloc_video_memory(sinfo);
		if (ret < 0) {
			dev_err(dev, "cannot allocate framebuffer: %d\n", ret);
			goto stop_clk;
		}
	}

	/* LCDC registers */
	info->fix.mmio_start = regs->start;
	info->fix.mmio_len = resource_size(regs);

	if (!request_mem_region(info->fix.mmio_start,
				info->fix.mmio_len, pdev->name)) {
		ret = -EBUSY;
		goto free_fb;
	}

	sinfo->mmio = ioremap(info->fix.mmio_start, info->fix.mmio_len);
	if (!sinfo->mmio) {
		dev_err(dev, "cannot map LCDC registers\n");
		ret = -ENOMEM;
		goto release_mem;
	}

	/* Initialize PWM for contrast or backlight ("off") */
	init_contrast(sinfo);

	/* interrupt */
	ret = request_irq(sinfo->irq_base, atmel_lcdfb_interrupt, 0, pdev->name, info);
	if (ret) {
		dev_err(dev, "request_irq failed: %d\n", ret);
		goto unmap_mmio;
	}

	/* Some operations on the LCDC might sleep and
	 * require a preemptible task context */
	INIT_WORK(&sinfo->task, atmel_lcdfb_task);

	ret = atmel_lcdfb_init_fbinfo(sinfo);
	if (ret < 0) {
		dev_err(dev, "init fbinfo failed: %d\n", ret);
		goto unregister_irqs;
	}

	ret = atmel_lcdfb_set_par(info);
	if (ret < 0) {
		dev_err(dev, "set par failed: %d\n", ret);
		goto unregister_irqs;
	}

	dev_set_drvdata(dev, info);

	/*
	 * Tell the world that we're ready to go
	 */
	ret = register_framebuffer(info);
	if (ret < 0) {
		dev_err(dev, "failed to register framebuffer device: %d\n", ret);
		goto reset_drvdata;
	}

	/* Power up the LCDC screen */
	atmel_lcdfb_power_control(sinfo, 1);

	dev_info(dev, "fb%d: Atmel LCDC at 0x%08lx (mapped at %p), irq %d\n",
		       info->node, info->fix.mmio_start, sinfo->mmio, sinfo->irq_base);

	return 0;

reset_drvdata:
	dev_set_drvdata(dev, NULL);
	fb_dealloc_cmap(&info->cmap);
unregister_irqs:
	cancel_work_sync(&sinfo->task);
	free_irq(sinfo->irq_base, info);
unmap_mmio:
	exit_backlight(sinfo);
	iounmap(sinfo->mmio);
release_mem:
 	release_mem_region(info->fix.mmio_start, info->fix.mmio_len);
free_fb:
	if (map)
		iounmap(info->screen_base);
	else
		atmel_lcdfb_free_video_memory(sinfo);

release_intmem:
	if (map)
		release_mem_region(info->fix.smem_start, info->fix.smem_len);
stop_clk:
	atmel_lcdfb_stop_clock(sinfo);
	clk_put(sinfo->lcdc_clk);
put_bus_clk:
	clk_put(sinfo->bus_clk);
free_info:
	framebuffer_release(info);
out:
	dev_dbg(dev, "%s FAILED\n", __func__);
	return ret;
}

static int __exit atmel_lcdfb_remove(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct fb_info *info = dev_get_drvdata(dev);
	struct atmel_lcdfb_info *sinfo;

	if (!info || !info->par)
		return 0;
	sinfo = info->par;

	cancel_work_sync(&sinfo->task);
	exit_backlight(sinfo);
	atmel_lcdfb_power_control(sinfo, 0);
	unregister_framebuffer(info);
	atmel_lcdfb_stop_clock(sinfo);
	clk_put(sinfo->lcdc_clk);
	clk_put(sinfo->bus_clk);
	fb_dealloc_cmap(&info->cmap);
	free_irq(sinfo->irq_base, info);
	iounmap(sinfo->mmio);
 	release_mem_region(info->fix.mmio_start, info->fix.mmio_len);
	if (platform_get_resource(pdev, IORESOURCE_MEM, 1)) {
		iounmap(info->screen_base);
		release_mem_region(info->fix.smem_start, info->fix.smem_len);
	} else {
		atmel_lcdfb_free_video_memory(sinfo);
	}

	framebuffer_release(info);

	return 0;
}

#ifdef CONFIG_PM

static int atmel_lcdfb_suspend(struct platform_device *pdev, pm_message_t mesg)
{
	struct fb_info *info = platform_get_drvdata(pdev);
	struct atmel_lcdfb_info *sinfo = info->par;

	/*
	 * We don't want to handle interrupts while the clock is
	 * stopped. It may take forever.
	 */
	lcdc_writel(sinfo, ATMEL_LCDC_IDR, ~0U);

	sinfo->saved_lcdcon = lcdc_readl(sinfo, ATMEL_LCDC_CONTRAST_CTR);
	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, 0);
	atmel_lcdfb_power_control(sinfo, 0);
	atmel_lcdfb_stop(sinfo);
	atmel_lcdfb_stop_clock(sinfo);

	return 0;
}

static int atmel_lcdfb_resume(struct platform_device *pdev)
{
	struct fb_info *info = platform_get_drvdata(pdev);
	struct atmel_lcdfb_info *sinfo = info->par;

	atmel_lcdfb_start_clock(sinfo);
	atmel_lcdfb_start(sinfo);
	atmel_lcdfb_power_control(sinfo, 1);
	lcdc_writel(sinfo, ATMEL_LCDC_CONTRAST_CTR, sinfo->saved_lcdcon);

	/* Enable FIFO & DMA errors */
	lcdc_writel(sinfo, ATMEL_LCDC_IER, ATMEL_LCDC_UFLWI
			| ATMEL_LCDC_OWRI | ATMEL_LCDC_MERI);

	return 0;
}

#else
#define atmel_lcdfb_suspend	NULL
#define atmel_lcdfb_resume	NULL
#endif

static struct platform_driver atmel_lcdfb_driver = {
	.remove		= __exit_p(atmel_lcdfb_remove),
	.suspend	= atmel_lcdfb_suspend,
	.resume		= atmel_lcdfb_resume,
	.driver		= {
		.name	= "atmel_lcdfb",
		.of_match_table	= atmel_lcdfb_dt_ids,
	},
};

module_platform_driver_probe(atmel_lcdfb_driver, atmel_lcdfb_probe);

MODULE_DESCRIPTION("AT91 LCD Controller framebuffer driver");
MODULE_AUTHOR("Nicolas Ferre <nicolas.ferre@atmel.com>");
MODULE_LICENSE("GPL");