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- // 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 <[email protected]>");
- MODULE_DESCRIPTION("Cirrus Logic EP93XX ADC driver");
- MODULE_LICENSE("GPL");
- MODULE_ALIAS("platform:ep93xx-adc");
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