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Diffstat (limited to '')
| -rw-r--r-- | drivers/iio/adc/ep93xx_adc.c | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/drivers/iio/adc/ep93xx_adc.c b/drivers/iio/adc/ep93xx_adc.c new file mode 100644 index 000000000..fd5a9404c --- /dev/null +++ b/drivers/iio/adc/ep93xx_adc.c @@ -0,0 +1,242 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Driver for ADC module on the Cirrus Logic EP93xx series of SoCs + * + * Copyright (C) 2015 Alexander Sverdlin + * + * The driver uses polling to get the conversion status. According to EP93xx + * datasheets, reading ADCResult register starts the conversion, but user is also + * responsible for ensuring that delay between adjacent conversion triggers is + * long enough so that maximum allowed conversion rate is not exceeded. This + * basically renders IRQ mode unusable. + */ + +#include <linux/clk.h> +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/err.h> +#include <linux/iio/iio.h> +#include <linux/io.h> +#include <linux/irqflags.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/platform_device.h> + +/* + * This code could benefit from real HR Timers, but jiffy granularity would + * lower ADC conversion rate down to CONFIG_HZ, so we fallback to busy wait + * in such case. + * + * HR Timers-based version loads CPU only up to 10% during back to back ADC + * conversion, while busy wait-based version consumes whole CPU power. + */ +#ifdef CONFIG_HIGH_RES_TIMERS +#define ep93xx_adc_delay(usmin, usmax) usleep_range(usmin, usmax) +#else +#define ep93xx_adc_delay(usmin, usmax) udelay(usmin) +#endif + +#define EP93XX_ADC_RESULT 0x08 +#define EP93XX_ADC_SDR BIT(31) +#define EP93XX_ADC_SWITCH 0x18 +#define EP93XX_ADC_SW_LOCK 0x20 + +struct ep93xx_adc_priv { + struct clk *clk; + void __iomem *base; + int lastch; + struct mutex lock; +}; + +#define EP93XX_ADC_CH(index, dname, swcfg) { \ + .type = IIO_VOLTAGE, \ + .indexed = 1, \ + .channel = index, \ + .address = swcfg, \ + .datasheet_name = dname, \ + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ + .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE) | \ + BIT(IIO_CHAN_INFO_OFFSET), \ +} + +/* + * Numbering scheme for channels 0..4 is defined in EP9301 and EP9302 datasheets. + * EP9307, EP9312 and EP9312 have 3 channels more (total 8), but the numbering is + * not defined. So the last three are numbered randomly, let's say. + */ +static const struct iio_chan_spec ep93xx_adc_channels[8] = { + EP93XX_ADC_CH(0, "YM", 0x608), + EP93XX_ADC_CH(1, "SXP", 0x680), + EP93XX_ADC_CH(2, "SXM", 0x640), + EP93XX_ADC_CH(3, "SYP", 0x620), + EP93XX_ADC_CH(4, "SYM", 0x610), + EP93XX_ADC_CH(5, "XP", 0x601), + EP93XX_ADC_CH(6, "XM", 0x602), + EP93XX_ADC_CH(7, "YP", 0x604), +}; + +static int ep93xx_read_raw(struct iio_dev *iiodev, + struct iio_chan_spec const *channel, int *value, + int *shift, long mask) +{ + struct ep93xx_adc_priv *priv = iio_priv(iiodev); + unsigned long timeout; + int ret; + + switch (mask) { + case IIO_CHAN_INFO_RAW: + mutex_lock(&priv->lock); + if (priv->lastch != channel->channel) { + priv->lastch = channel->channel; + /* + * Switch register is software-locked, unlocking must be + * immediately followed by write + */ + local_irq_disable(); + writel_relaxed(0xAA, priv->base + EP93XX_ADC_SW_LOCK); + writel_relaxed(channel->address, + priv->base + EP93XX_ADC_SWITCH); + local_irq_enable(); + /* + * Settling delay depends on module clock and could be + * 2ms or 500us + */ + ep93xx_adc_delay(2000, 2000); + } + /* Start the conversion, eventually discarding old result */ + readl_relaxed(priv->base + EP93XX_ADC_RESULT); + /* Ensure maximum conversion rate is not exceeded */ + ep93xx_adc_delay(DIV_ROUND_UP(1000000, 925), + DIV_ROUND_UP(1000000, 925)); + /* At this point conversion must be completed, but anyway... */ + ret = IIO_VAL_INT; + timeout = jiffies + msecs_to_jiffies(1) + 1; + while (1) { + u32 t; + + t = readl_relaxed(priv->base + EP93XX_ADC_RESULT); + if (t & EP93XX_ADC_SDR) { + *value = sign_extend32(t, 15); + break; + } + + if (time_after(jiffies, timeout)) { + dev_err(&iiodev->dev, "Conversion timeout\n"); + ret = -ETIMEDOUT; + break; + } + + cpu_relax(); + } + mutex_unlock(&priv->lock); + return ret; + + case IIO_CHAN_INFO_OFFSET: + /* According to datasheet, range is -25000..25000 */ + *value = 25000; + return IIO_VAL_INT; + + case IIO_CHAN_INFO_SCALE: + /* Typical supply voltage is 3.3v */ + *value = (1ULL << 32) * 3300 / 50000; + *shift = 32; + return IIO_VAL_FRACTIONAL_LOG2; + } + + return -EINVAL; +} + +static const struct iio_info ep93xx_adc_info = { + .read_raw = ep93xx_read_raw, +}; + +static int ep93xx_adc_probe(struct platform_device *pdev) +{ + int ret; + struct iio_dev *iiodev; + struct ep93xx_adc_priv *priv; + struct clk *pclk; + + iiodev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv)); + if (!iiodev) + return -ENOMEM; + priv = iio_priv(iiodev); + + priv->base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(priv->base)) + return PTR_ERR(priv->base); + + iiodev->name = dev_name(&pdev->dev); + iiodev->modes = INDIO_DIRECT_MODE; + iiodev->info = &ep93xx_adc_info; + iiodev->num_channels = ARRAY_SIZE(ep93xx_adc_channels); + iiodev->channels = ep93xx_adc_channels; + + priv->lastch = -1; + mutex_init(&priv->lock); + + platform_set_drvdata(pdev, iiodev); + + priv->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(priv->clk)) { + dev_err(&pdev->dev, "Cannot obtain clock\n"); + return PTR_ERR(priv->clk); + } + + pclk = clk_get_parent(priv->clk); + if (!pclk) { + dev_warn(&pdev->dev, "Cannot obtain parent clock\n"); + } else { + /* + * This is actually a place for improvement: + * EP93xx ADC supports two clock divisors -- 4 and 16, + * resulting in conversion rates 3750 and 925 samples per second + * with 500us or 2ms settling time respectively. + * One might find this interesting enough to be configurable. + */ + ret = clk_set_rate(priv->clk, clk_get_rate(pclk) / 16); + if (ret) + dev_warn(&pdev->dev, "Cannot set clock rate\n"); + /* + * We can tolerate rate setting failure because the module should + * work in any case. + */ + } + + ret = clk_prepare_enable(priv->clk); + if (ret) { + dev_err(&pdev->dev, "Cannot enable clock\n"); + return ret; + } + + ret = iio_device_register(iiodev); + if (ret) + clk_disable_unprepare(priv->clk); + + return ret; +} + +static int ep93xx_adc_remove(struct platform_device *pdev) +{ + struct iio_dev *iiodev = platform_get_drvdata(pdev); + struct ep93xx_adc_priv *priv = iio_priv(iiodev); + + iio_device_unregister(iiodev); + clk_disable_unprepare(priv->clk); + + return 0; +} + +static struct platform_driver ep93xx_adc_driver = { + .driver = { + .name = "ep93xx-adc", + }, + .probe = ep93xx_adc_probe, + .remove = ep93xx_adc_remove, +}; +module_platform_driver(ep93xx_adc_driver); + +MODULE_AUTHOR("Alexander Sverdlin <alexander.sverdlin@gmail.com>"); +MODULE_DESCRIPTION("Cirrus Logic EP93XX ADC driver"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:ep93xx-adc"); |