xref: /openbmc/linux/drivers/spi/spi-microchip-core.c (revision 7e24a55b2122746c2eef192296fc84624354f895)

// SPDX-License-Identifier: (GPL-2.0)
/*
 * Microchip CoreSPI SPI controller driver
 *
 * Copyright (c) 2018-2022 Microchip Technology Inc. and its subsidiaries
 *
 * Author: Daire McNamara <daire.mcnamara@microchip.com>
 * Author: Conor Dooley <conor.dooley@microchip.com>
 *
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/spi/spi.h>

#define MAX_LEN				(0xffff)
#define MAX_CS				(1)
#define DEFAULT_FRAMESIZE		(8)
#define FIFO_DEPTH			(32)
#define CLK_GEN_MODE1_MAX		(255)
#define CLK_GEN_MODE0_MAX		(15)
#define CLK_GEN_MIN			(0)
#define MODE_X_MASK_SHIFT		(24)

#define CONTROL_ENABLE			BIT(0)
#define CONTROL_MASTER			BIT(1)
#define CONTROL_RX_DATA_INT		BIT(4)
#define CONTROL_TX_DATA_INT		BIT(5)
#define CONTROL_RX_OVER_INT		BIT(6)
#define CONTROL_TX_UNDER_INT		BIT(7)
#define CONTROL_SPO			BIT(24)
#define CONTROL_SPH			BIT(25)
#define CONTROL_SPS			BIT(26)
#define CONTROL_FRAMEURUN		BIT(27)
#define CONTROL_CLKMODE			BIT(28)
#define CONTROL_BIGFIFO			BIT(29)
#define CONTROL_OENOFF			BIT(30)
#define CONTROL_RESET			BIT(31)

#define CONTROL_MODE_MASK		GENMASK(3, 2)
#define  MOTOROLA_MODE			(0)
#define CONTROL_FRAMECNT_MASK		GENMASK(23, 8)
#define CONTROL_FRAMECNT_SHIFT		(8)

#define STATUS_ACTIVE			BIT(14)
#define STATUS_SSEL			BIT(13)
#define STATUS_FRAMESTART		BIT(12)
#define STATUS_TXFIFO_EMPTY_NEXT_READ	BIT(11)
#define STATUS_TXFIFO_EMPTY		BIT(10)
#define STATUS_TXFIFO_FULL_NEXT_WRITE	BIT(9)
#define STATUS_TXFIFO_FULL		BIT(8)
#define STATUS_RXFIFO_EMPTY_NEXT_READ	BIT(7)
#define STATUS_RXFIFO_EMPTY		BIT(6)
#define STATUS_RXFIFO_FULL_NEXT_WRITE	BIT(5)
#define STATUS_RXFIFO_FULL		BIT(4)
#define STATUS_TX_UNDERRUN		BIT(3)
#define STATUS_RX_OVERFLOW		BIT(2)
#define STATUS_RXDAT_RXED		BIT(1)
#define STATUS_TXDAT_SENT		BIT(0)

#define INT_TXDONE			BIT(0)
#define INT_RXRDY			BIT(1)
#define INT_RX_CHANNEL_OVERFLOW		BIT(2)
#define INT_TX_CHANNEL_UNDERRUN		BIT(3)

#define INT_ENABLE_MASK (CONTROL_RX_DATA_INT | CONTROL_TX_DATA_INT | \
			 CONTROL_RX_OVER_INT | CONTROL_TX_UNDER_INT)

#define REG_CONTROL		(0x00)
#define REG_FRAME_SIZE		(0x04)
#define  FRAME_SIZE_MASK	GENMASK(5, 0)
#define REG_STATUS		(0x08)
#define REG_INT_CLEAR		(0x0c)
#define REG_RX_DATA		(0x10)
#define REG_TX_DATA		(0x14)
#define REG_CLK_GEN		(0x18)
#define REG_SLAVE_SELECT	(0x1c)
#define  SSEL_MASK		GENMASK(7, 0)
#define  SSEL_DIRECT		BIT(8)
#define  SSELOUT_SHIFT		9
#define  SSELOUT		BIT(SSELOUT_SHIFT)
#define REG_MIS			(0x20)
#define REG_RIS			(0x24)
#define REG_CONTROL2		(0x28)
#define REG_COMMAND		(0x2c)
#define  COMMAND_CLRFRAMECNT	BIT(4)
#define  COMMAND_TXFIFORST		BIT(3)
#define  COMMAND_RXFIFORST		BIT(2)
#define REG_PKTSIZE		(0x30)
#define REG_CMD_SIZE		(0x34)
#define REG_HWSTATUS		(0x38)
#define REG_STAT8		(0x3c)
#define REG_CTRL2		(0x48)
#define REG_FRAMESUP		(0x50)

struct mchp_corespi {
	void __iomem *regs;
	struct clk *clk;
	const u8 *tx_buf;
	u8 *rx_buf;
	u32 clk_gen; /* divider for spi output clock generated by the controller */
	u32 clk_mode;
	u32 pending_slave_select;
	int irq;
	int tx_len;
	int rx_len;
	int pending;
};

static inline u32 mchp_corespi_read(struct mchp_corespi *spi, unsigned int reg)
{
	return readl(spi->regs + reg);
}

static inline void mchp_corespi_write(struct mchp_corespi *spi, unsigned int reg, u32 val)
{
	writel(val, spi->regs + reg);
}

static inline void mchp_corespi_disable(struct mchp_corespi *spi)
{
	u32 control = mchp_corespi_read(spi, REG_CONTROL);

	control &= ~CONTROL_ENABLE;

	mchp_corespi_write(spi, REG_CONTROL, control);
}

static inline void mchp_corespi_read_fifo(struct mchp_corespi *spi)
{
	u8 data;
	int fifo_max, i = 0;

	fifo_max = min(spi->rx_len, FIFO_DEPTH);

	while ((i < fifo_max) && !(mchp_corespi_read(spi, REG_STATUS) & STATUS_RXFIFO_EMPTY)) {
		data = mchp_corespi_read(spi, REG_RX_DATA);

		if (spi->rx_buf)
			*spi->rx_buf++ = data;
		i++;
	}
	spi->rx_len -= i;
	spi->pending -= i;
}

static void mchp_corespi_enable_ints(struct mchp_corespi *spi)
{
	u32 control = mchp_corespi_read(spi, REG_CONTROL);

	control |= INT_ENABLE_MASK;
	mchp_corespi_write(spi, REG_CONTROL, control);
}

static void mchp_corespi_disable_ints(struct mchp_corespi *spi)
{
	u32 control = mchp_corespi_read(spi, REG_CONTROL);

	control &= ~INT_ENABLE_MASK;
	mchp_corespi_write(spi, REG_CONTROL, control);
}

static inline void mchp_corespi_set_xfer_size(struct mchp_corespi *spi, int len)
{
	u32 control;
	u32 lenpart;
	u32 frames = mchp_corespi_read(spi, REG_FRAMESUP);

	/*
	 * Writing to FRAMECNT in REG_CONTROL will reset the frame count, taking
	 * a shortcut requires an explicit clear.
	 */
	if (frames == len) {
		mchp_corespi_write(spi, REG_COMMAND, COMMAND_CLRFRAMECNT);
		return;
	}

	/*
	 * The lower 16 bits of the frame count are stored in the control reg
	 * for legacy reasons, but the upper 16 written to a different register:
	 * FRAMESUP. While both the upper and lower bits can be *READ* from the
	 * FRAMESUP register, writing to the lower 16 bits is (supposedly) a NOP.
	 *
	 * The driver used to disable the controller while modifying the frame
	 * count, and mask off the lower 16 bits of len while writing to
	 * FRAMES_UP. When the driver was changed to disable the controller as
	 * infrequently as possible, it was discovered that the logic of
	 * lenpart = len & 0xffff_0000
	 * write(REG_FRAMESUP, lenpart)
	 * would actually write zeros into the lower 16 bits on an mpfs250t-es,
	 * despite documentation stating these bits were read-only.
	 * Writing len unmasked into FRAMES_UP ensures those bits aren't zeroed
	 * on an mpfs250t-es and will be a NOP for the lower 16 bits on hardware
	 * that matches the documentation.
	 */
	lenpart = len & 0xffff;
	control = mchp_corespi_read(spi, REG_CONTROL);
	control &= ~CONTROL_FRAMECNT_MASK;
	control |= lenpart << CONTROL_FRAMECNT_SHIFT;
	mchp_corespi_write(spi, REG_CONTROL, control);
	mchp_corespi_write(spi, REG_FRAMESUP, len);
}

static inline void mchp_corespi_write_fifo(struct mchp_corespi *spi)
{
	u8 byte;
	int fifo_max, i = 0;

	fifo_max = min(spi->tx_len, FIFO_DEPTH);
	mchp_corespi_set_xfer_size(spi, fifo_max);

	while ((i < fifo_max) && !(mchp_corespi_read(spi, REG_STATUS) & STATUS_TXFIFO_FULL)) {
		byte = spi->tx_buf ? *spi->tx_buf++ : 0xaa;
		mchp_corespi_write(spi, REG_TX_DATA, byte);
		i++;
	}

	spi->tx_len -= i;
	spi->pending += i;
}

static inline void mchp_corespi_set_framesize(struct mchp_corespi *spi, int bt)
{
	u32 frame_size = mchp_corespi_read(spi, REG_FRAME_SIZE);
	u32 control;

	if ((frame_size & FRAME_SIZE_MASK) == bt)
		return;

	/*
	 * Disable the SPI controller. Writes to the frame size have
	 * no effect when the controller is enabled.
	 */
	control = mchp_corespi_read(spi, REG_CONTROL);
	control &= ~CONTROL_ENABLE;
	mchp_corespi_write(spi, REG_CONTROL, control);

	mchp_corespi_write(spi, REG_FRAME_SIZE, bt);

	control |= CONTROL_ENABLE;
	mchp_corespi_write(spi, REG_CONTROL, control);
}

static void mchp_corespi_set_cs(struct spi_device *spi, bool disable)
{
	u32 reg;
	struct mchp_corespi *corespi = spi_controller_get_devdata(spi->controller);

	reg = mchp_corespi_read(corespi, REG_SLAVE_SELECT);
	reg &= ~BIT(spi_get_chipselect(spi, 0));
	reg |= !disable << spi_get_chipselect(spi, 0);
	corespi->pending_slave_select = reg;

	/*
	 * Only deassert chip select immediately. Writing to some registers
	 * requires the controller to be disabled, which results in the
	 * output pins being tristated and can cause the SCLK and MOSI lines
	 * to transition. Therefore asserting the chip select is deferred
	 * until just before writing to the TX FIFO, to ensure the device
	 * doesn't see any spurious clock transitions whilst CS is enabled.
	 */
	if (((spi->mode & SPI_CS_HIGH) == 0) == disable)
		mchp_corespi_write(corespi, REG_SLAVE_SELECT, reg);
}

static int mchp_corespi_setup(struct spi_device *spi)
{
	struct mchp_corespi *corespi = spi_controller_get_devdata(spi->controller);
	u32 reg;

	/*
	 * Active high targets need to be specifically set to their inactive
	 * states during probe by adding them to the "control group" & thus
	 * driving their select line low.
	 */
	if (spi->mode & SPI_CS_HIGH) {
		reg = mchp_corespi_read(corespi, REG_SLAVE_SELECT);
		reg |= BIT(spi_get_chipselect(spi, 0));
		corespi->pending_slave_select = reg;
		mchp_corespi_write(corespi, REG_SLAVE_SELECT, reg);
	}
	return 0;
}

static void mchp_corespi_init(struct spi_controller *host, struct mchp_corespi *spi)
{
	unsigned long clk_hz;
	u32 control = mchp_corespi_read(spi, REG_CONTROL);

	control &= ~CONTROL_ENABLE;
	mchp_corespi_write(spi, REG_CONTROL, control);

	control |= CONTROL_MASTER;
	control &= ~CONTROL_MODE_MASK;
	control |= MOTOROLA_MODE;

	/*
	 * The controller must be configured so that it doesn't remove Chip
	 * Select until the entire message has been transferred, even if at
	 * some points TX FIFO becomes empty.
	 *
	 * BIGFIFO mode is also enabled, which sets the fifo depth to 32 frames
	 * for the 8 bit transfers that this driver uses.
	 */
	control |= CONTROL_SPS | CONTROL_BIGFIFO;

	mchp_corespi_write(spi, REG_CONTROL, control);

	mchp_corespi_set_framesize(spi, DEFAULT_FRAMESIZE);

	/* max. possible spi clock rate is the apb clock rate */
	clk_hz = clk_get_rate(spi->clk);
	host->max_speed_hz = clk_hz;

	mchp_corespi_enable_ints(spi);

	/*
	 * It is required to enable direct mode, otherwise control over the chip
	 * select is relinquished to the hardware. SSELOUT is enabled too so we
	 * can deal with active high targets.
	 */
	spi->pending_slave_select = SSELOUT | SSEL_DIRECT;
	mchp_corespi_write(spi, REG_SLAVE_SELECT, spi->pending_slave_select);

	control = mchp_corespi_read(spi, REG_CONTROL);

	control &= ~CONTROL_RESET;
	control |= CONTROL_ENABLE;

	mchp_corespi_write(spi, REG_CONTROL, control);
}

static inline void mchp_corespi_set_clk_gen(struct mchp_corespi *spi)
{
	u32 control;

	control = mchp_corespi_read(spi, REG_CONTROL);
	if (spi->clk_mode)
		control |= CONTROL_CLKMODE;
	else
		control &= ~CONTROL_CLKMODE;

	mchp_corespi_write(spi, REG_CLK_GEN, spi->clk_gen);
	mchp_corespi_write(spi, REG_CONTROL, control);
}

static inline void mchp_corespi_set_mode(struct mchp_corespi *spi, unsigned int mode)
{
	u32 mode_val;
	u32 control = mchp_corespi_read(spi, REG_CONTROL);

	switch (mode & SPI_MODE_X_MASK) {
	case SPI_MODE_0:
		mode_val = 0;
		break;
	case SPI_MODE_1:
		mode_val = CONTROL_SPH;
		break;
	case SPI_MODE_2:
		mode_val = CONTROL_SPO;
		break;
	case SPI_MODE_3:
		mode_val = CONTROL_SPH | CONTROL_SPO;
		break;
	}

	/*
	 * Disable the SPI controller. Writes to the frame protocol have
	 * no effect when the controller is enabled.
	 */

	control &= ~CONTROL_ENABLE;
	mchp_corespi_write(spi, REG_CONTROL, control);

	control &= ~(SPI_MODE_X_MASK << MODE_X_MASK_SHIFT);
	control |= mode_val;

	mchp_corespi_write(spi, REG_CONTROL, control);

	control |= CONTROL_ENABLE;
	mchp_corespi_write(spi, REG_CONTROL, control);
}

static irqreturn_t mchp_corespi_interrupt(int irq, void *dev_id)
{
	struct spi_controller *host = dev_id;
	struct mchp_corespi *spi = spi_controller_get_devdata(host);
	u32 intfield = mchp_corespi_read(spi, REG_MIS) & 0xf;
	bool finalise = false;

	/* Interrupt line may be shared and not for us at all */
	if (intfield == 0)
		return IRQ_NONE;

	if (intfield & INT_TXDONE)
		mchp_corespi_write(spi, REG_INT_CLEAR, INT_TXDONE);

	if (intfield & INT_RXRDY) {
		mchp_corespi_write(spi, REG_INT_CLEAR, INT_RXRDY);

		if (spi->rx_len)
			mchp_corespi_read_fifo(spi);
	}

	if (!spi->rx_len && !spi->tx_len)
		finalise = true;

	if (intfield & INT_RX_CHANNEL_OVERFLOW) {
		mchp_corespi_write(spi, REG_INT_CLEAR, INT_RX_CHANNEL_OVERFLOW);
		finalise = true;
		dev_err(&host->dev,
			"%s: RX OVERFLOW: rxlen: %d, txlen: %d\n", __func__,
			spi->rx_len, spi->tx_len);
	}

	if (intfield & INT_TX_CHANNEL_UNDERRUN) {
		mchp_corespi_write(spi, REG_INT_CLEAR, INT_TX_CHANNEL_UNDERRUN);
		finalise = true;
		dev_err(&host->dev,
			"%s: TX UNDERFLOW: rxlen: %d, txlen: %d\n", __func__,
			spi->rx_len, spi->tx_len);
	}

	if (finalise)
		spi_finalize_current_transfer(host);

	return IRQ_HANDLED;
}

static int mchp_corespi_calculate_clkgen(struct mchp_corespi *spi,
					 unsigned long target_hz)
{
	unsigned long clk_hz, spi_hz, clk_gen;

	clk_hz = clk_get_rate(spi->clk);
	if (!clk_hz)
		return -EINVAL;
	spi_hz = min(target_hz, clk_hz);

	/*
	 * There are two possible clock modes for the controller generated
	 * clock's division ratio:
	 * CLK_MODE = 0: 1 / (2^(CLK_GEN + 1)) where CLK_GEN = 0 to 15.
	 * CLK_MODE = 1: 1 / (2 * CLK_GEN + 1) where CLK_GEN = 0 to 255.
	 * First try mode 1, fall back to 0 and if we have tried both modes and
	 * we /still/ can't get a good setting, we then throw the toys out of
	 * the pram and give up
	 * clk_gen is the register name for the clock divider on MPFS.
	 */
	clk_gen = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1;
	if (clk_gen > CLK_GEN_MODE1_MAX || clk_gen <= CLK_GEN_MIN) {
		clk_gen = DIV_ROUND_UP(clk_hz, spi_hz);
		clk_gen = fls(clk_gen) - 1;

		if (clk_gen > CLK_GEN_MODE0_MAX)
			return -EINVAL;

		spi->clk_mode = 0;
	} else {
		spi->clk_mode = 1;
	}

	spi->clk_gen = clk_gen;
	return 0;
}

static int mchp_corespi_transfer_one(struct spi_controller *host,
				     struct spi_device *spi_dev,
				     struct spi_transfer *xfer)
{
	struct mchp_corespi *spi = spi_controller_get_devdata(host);
	int ret;

	ret = mchp_corespi_calculate_clkgen(spi, (unsigned long)xfer->speed_hz);
	if (ret) {
		dev_err(&host->dev, "failed to set clk_gen for target %u Hz\n", xfer->speed_hz);
		return ret;
	}

	mchp_corespi_set_clk_gen(spi);

	spi->tx_buf = xfer->tx_buf;
	spi->rx_buf = xfer->rx_buf;
	spi->tx_len = xfer->len;
	spi->rx_len = xfer->len;
	spi->pending = 0;

	mchp_corespi_set_xfer_size(spi, (spi->tx_len > FIFO_DEPTH)
				   ? FIFO_DEPTH : spi->tx_len);

	mchp_corespi_write(spi, REG_COMMAND, COMMAND_RXFIFORST | COMMAND_TXFIFORST);

	mchp_corespi_write(spi, REG_SLAVE_SELECT, spi->pending_slave_select);

	while (spi->tx_len)
		mchp_corespi_write_fifo(spi);

	return 1;
}

static int mchp_corespi_prepare_message(struct spi_controller *host,
					struct spi_message *msg)
{
	struct spi_device *spi_dev = msg->spi;
	struct mchp_corespi *spi = spi_controller_get_devdata(host);

	mchp_corespi_set_framesize(spi, DEFAULT_FRAMESIZE);
	mchp_corespi_set_mode(spi, spi_dev->mode);

	return 0;
}

static int mchp_corespi_probe(struct platform_device *pdev)
{
	struct spi_controller *host;
	struct mchp_corespi *spi;
	struct resource *res;
	u32 num_cs;
	int ret = 0;

	host = devm_spi_alloc_host(&pdev->dev, sizeof(*spi));
	if (!host)
		return dev_err_probe(&pdev->dev, -ENOMEM,
				     "unable to allocate host for SPI controller\n");

	platform_set_drvdata(pdev, host);

	if (of_property_read_u32(pdev->dev.of_node, "num-cs", &num_cs))
		num_cs = MAX_CS;

	host->num_chipselect = num_cs;
	host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
	host->setup = mchp_corespi_setup;
	host->bits_per_word_mask = SPI_BPW_MASK(8);
	host->transfer_one = mchp_corespi_transfer_one;
	host->prepare_message = mchp_corespi_prepare_message;
	host->set_cs = mchp_corespi_set_cs;
	host->dev.of_node = pdev->dev.of_node;

	spi = spi_controller_get_devdata(host);

	spi->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
	if (IS_ERR(spi->regs))
		return PTR_ERR(spi->regs);

	spi->irq = platform_get_irq(pdev, 0);
	if (spi->irq < 0)
		return spi->irq;

	ret = devm_request_irq(&pdev->dev, spi->irq, mchp_corespi_interrupt,
			       IRQF_SHARED, dev_name(&pdev->dev), host);
	if (ret)
		return dev_err_probe(&pdev->dev, ret,
				     "could not request irq\n");

	spi->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(spi->clk))
		return dev_err_probe(&pdev->dev, PTR_ERR(spi->clk),
				     "could not get clk\n");

	ret = clk_prepare_enable(spi->clk);
	if (ret)
		return dev_err_probe(&pdev->dev, ret,
				     "failed to enable clock\n");

	mchp_corespi_init(host, spi);

	ret = devm_spi_register_controller(&pdev->dev, host);
	if (ret) {
		mchp_corespi_disable(spi);
		clk_disable_unprepare(spi->clk);
		return dev_err_probe(&pdev->dev, ret,
				     "unable to register host for SPI controller\n");
	}

	dev_info(&pdev->dev, "Registered SPI controller %d\n", host->bus_num);

	return 0;
}

static void mchp_corespi_remove(struct platform_device *pdev)
{
	struct spi_controller *host  = platform_get_drvdata(pdev);
	struct mchp_corespi *spi = spi_controller_get_devdata(host);

	mchp_corespi_disable_ints(spi);
	clk_disable_unprepare(spi->clk);
	mchp_corespi_disable(spi);
}

#define MICROCHIP_SPI_PM_OPS (NULL)

/*
 * Platform driver data structure
 */

#if defined(CONFIG_OF)
static const struct of_device_id mchp_corespi_dt_ids[] = {
	{ .compatible = "microchip,mpfs-spi" },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, mchp_corespi_dt_ids);
#endif

static struct platform_driver mchp_corespi_driver = {
	.probe = mchp_corespi_probe,
	.driver = {
		.name = "microchip-corespi",
		.pm = MICROCHIP_SPI_PM_OPS,
		.of_match_table = of_match_ptr(mchp_corespi_dt_ids),
	},
	.remove_new = mchp_corespi_remove,
};
module_platform_driver(mchp_corespi_driver);
MODULE_DESCRIPTION("Microchip coreSPI SPI controller driver");
MODULE_AUTHOR("Daire McNamara <daire.mcnamara@microchip.com>");
MODULE_AUTHOR("Conor Dooley <conor.dooley@microchip.com>");
MODULE_LICENSE("GPL");