1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Driver for ADC module on the Cirrus Logic EP93xx series of SoCs 4 * 5 * Copyright (C) 2015 Alexander Sverdlin 6 * 7 * The driver uses polling to get the conversion status. According to EP93xx 8 * datasheets, reading ADCResult register starts the conversion, but user is also 9 * responsible for ensuring that delay between adjacent conversion triggers is 10 * long enough so that maximum allowed conversion rate is not exceeded. This 11 * basically renders IRQ mode unusable. 12 */ 13 14 #include <linux/clk.h> 15 #include <linux/delay.h> 16 #include <linux/device.h> 17 #include <linux/err.h> 18 #include <linux/iio/iio.h> 19 #include <linux/io.h> 20 #include <linux/irqflags.h> 21 #include <linux/module.h> 22 #include <linux/mutex.h> 23 #include <linux/platform_device.h> 24 25 /* 26 * This code could benefit from real HR Timers, but jiffy granularity would 27 * lower ADC conversion rate down to CONFIG_HZ, so we fallback to busy wait 28 * in such case. 29 * 30 * HR Timers-based version loads CPU only up to 10% during back to back ADC 31 * conversion, while busy wait-based version consumes whole CPU power. 32 */ 33 #ifdef CONFIG_HIGH_RES_TIMERS 34 #define ep93xx_adc_delay(usmin, usmax) usleep_range(usmin, usmax) 35 #else 36 #define ep93xx_adc_delay(usmin, usmax) udelay(usmin) 37 #endif 38 39 #define EP93XX_ADC_RESULT 0x08 40 #define EP93XX_ADC_SDR BIT(31) 41 #define EP93XX_ADC_SWITCH 0x18 42 #define EP93XX_ADC_SW_LOCK 0x20 43 44 struct ep93xx_adc_priv { 45 struct clk *clk; 46 void __iomem *base; 47 int lastch; 48 struct mutex lock; 49 }; 50 51 #define EP93XX_ADC_CH(index, dname, swcfg) { \ 52 .type = IIO_VOLTAGE, \ 53 .indexed = 1, \ 54 .channel = index, \ 55 .address = swcfg, \ 56 .datasheet_name = dname, \ 57 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ 58 .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) | \ 59 BIT(IIO_CHAN_INFO_OFFSET), \ 60 } 61 62 /* 63 * Numbering scheme for channels 0..4 is defined in EP9301 and EP9302 datasheets. 64 * EP9307, EP9312 and EP9312 have 3 channels more (total 8), but the numbering is 65 * not defined. So the last three are numbered randomly, let's say. 66 */ 67 static const struct iio_chan_spec ep93xx_adc_channels[8] = { 68 EP93XX_ADC_CH(0, "YM", 0x608), 69 EP93XX_ADC_CH(1, "SXP", 0x680), 70 EP93XX_ADC_CH(2, "SXM", 0x640), 71 EP93XX_ADC_CH(3, "SYP", 0x620), 72 EP93XX_ADC_CH(4, "SYM", 0x610), 73 EP93XX_ADC_CH(5, "XP", 0x601), 74 EP93XX_ADC_CH(6, "XM", 0x602), 75 EP93XX_ADC_CH(7, "YP", 0x604), 76 }; 77 78 static int ep93xx_read_raw(struct iio_dev *iiodev, 79 struct iio_chan_spec const *channel, int *value, 80 int *shift, long mask) 81 { 82 struct ep93xx_adc_priv *priv = iio_priv(iiodev); 83 unsigned long timeout; 84 int ret; 85 86 switch (mask) { 87 case IIO_CHAN_INFO_RAW: 88 mutex_lock(&priv->lock); 89 if (priv->lastch != channel->channel) { 90 priv->lastch = channel->channel; 91 /* 92 * Switch register is software-locked, unlocking must be 93 * immediately followed by write 94 */ 95 local_irq_disable(); 96 writel_relaxed(0xAA, priv->base + EP93XX_ADC_SW_LOCK); 97 writel_relaxed(channel->address, 98 priv->base + EP93XX_ADC_SWITCH); 99 local_irq_enable(); 100 /* 101 * Settling delay depends on module clock and could be 102 * 2ms or 500us 103 */ 104 ep93xx_adc_delay(2000, 2000); 105 } 106 /* Start the conversion, eventually discarding old result */ 107 readl_relaxed(priv->base + EP93XX_ADC_RESULT); 108 /* Ensure maximum conversion rate is not exceeded */ 109 ep93xx_adc_delay(DIV_ROUND_UP(1000000, 925), 110 DIV_ROUND_UP(1000000, 925)); 111 /* At this point conversion must be completed, but anyway... */ 112 ret = IIO_VAL_INT; 113 timeout = jiffies + msecs_to_jiffies(1) + 1; 114 while (1) { 115 u32 t; 116 117 t = readl_relaxed(priv->base + EP93XX_ADC_RESULT); 118 if (t & EP93XX_ADC_SDR) { 119 *value = sign_extend32(t, 15); 120 break; 121 } 122 123 if (time_after(jiffies, timeout)) { 124 dev_err(&iiodev->dev, "Conversion timeout\n"); 125 ret = -ETIMEDOUT; 126 break; 127 } 128 129 cpu_relax(); 130 } 131 mutex_unlock(&priv->lock); 132 return ret; 133 134 case IIO_CHAN_INFO_OFFSET: 135 /* According to datasheet, range is -25000..25000 */ 136 *value = 25000; 137 return IIO_VAL_INT; 138 139 case IIO_CHAN_INFO_SCALE: 140 /* Typical supply voltage is 3.3v */ 141 *value = (1ULL << 32) * 3300 / 50000; 142 *shift = 32; 143 return IIO_VAL_FRACTIONAL_LOG2; 144 } 145 146 return -EINVAL; 147 } 148 149 static const struct iio_info ep93xx_adc_info = { 150 .read_raw = ep93xx_read_raw, 151 }; 152 153 static int ep93xx_adc_probe(struct platform_device *pdev) 154 { 155 int ret; 156 struct iio_dev *iiodev; 157 struct ep93xx_adc_priv *priv; 158 struct clk *pclk; 159 160 iiodev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv)); 161 if (!iiodev) 162 return -ENOMEM; 163 priv = iio_priv(iiodev); 164 165 priv->base = devm_platform_ioremap_resource(pdev, 0); 166 if (IS_ERR(priv->base)) 167 return PTR_ERR(priv->base); 168 169 iiodev->name = dev_name(&pdev->dev); 170 iiodev->modes = INDIO_DIRECT_MODE; 171 iiodev->info = &ep93xx_adc_info; 172 iiodev->num_channels = ARRAY_SIZE(ep93xx_adc_channels); 173 iiodev->channels = ep93xx_adc_channels; 174 175 priv->lastch = -1; 176 mutex_init(&priv->lock); 177 178 platform_set_drvdata(pdev, iiodev); 179 180 priv->clk = devm_clk_get(&pdev->dev, NULL); 181 if (IS_ERR(priv->clk)) { 182 dev_err(&pdev->dev, "Cannot obtain clock\n"); 183 return PTR_ERR(priv->clk); 184 } 185 186 pclk = clk_get_parent(priv->clk); 187 if (!pclk) { 188 dev_warn(&pdev->dev, "Cannot obtain parent clock\n"); 189 } else { 190 /* 191 * This is actually a place for improvement: 192 * EP93xx ADC supports two clock divisors -- 4 and 16, 193 * resulting in conversion rates 3750 and 925 samples per second 194 * with 500us or 2ms settling time respectively. 195 * One might find this interesting enough to be configurable. 196 */ 197 ret = clk_set_rate(priv->clk, clk_get_rate(pclk) / 16); 198 if (ret) 199 dev_warn(&pdev->dev, "Cannot set clock rate\n"); 200 /* 201 * We can tolerate rate setting failure because the module should 202 * work in any case. 203 */ 204 } 205 206 ret = clk_prepare_enable(priv->clk); 207 if (ret) { 208 dev_err(&pdev->dev, "Cannot enable clock\n"); 209 return ret; 210 } 211 212 ret = iio_device_register(iiodev); 213 if (ret) 214 clk_disable_unprepare(priv->clk); 215 216 return ret; 217 } 218 219 static int ep93xx_adc_remove(struct platform_device *pdev) 220 { 221 struct iio_dev *iiodev = platform_get_drvdata(pdev); 222 struct ep93xx_adc_priv *priv = iio_priv(iiodev); 223 224 iio_device_unregister(iiodev); 225 clk_disable_unprepare(priv->clk); 226 227 return 0; 228 } 229 230 static struct platform_driver ep93xx_adc_driver = { 231 .driver = { 232 .name = "ep93xx-adc", 233 }, 234 .probe = ep93xx_adc_probe, 235 .remove = ep93xx_adc_remove, 236 }; 237 module_platform_driver(ep93xx_adc_driver); 238 239 MODULE_AUTHOR("Alexander Sverdlin <alexander.sverdlin@gmail.com>"); 240 MODULE_DESCRIPTION("Cirrus Logic EP93XX ADC driver"); 241 MODULE_LICENSE("GPL"); 242 MODULE_ALIAS("platform:ep93xx-adc"); 243