New driver adding support for ADC found on Cirrus Logic EP93xx series of SoCs.
Board specific code must take care to create platform device with all necessary
resources.
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
---
drivers/iio/adc/Kconfig | 11 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/ep93xx_adc.c | 253 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 265 insertions(+)
create mode 100644 drivers/iio/adc/ep93xx_adc.c
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 7868c74..2ee8b8b 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -172,6 +172,17 @@ config DA9150_GPADC
To compile this driver as a module, choose M here: the module will be
called berlin2-adc.
+config EP93XX_ADC
+ tristate "Cirrus Logic EP93XX ADC driver"
+ depends on ARCH_EP93XX
+ help
+ Driver for the ADC module on the EP93XX series of SoC from Cirrus Logic.
+ It's recommended to switch on CONFIG_HIGH_RES_TIMERS option, in this
+ case driver will reduce its CPU usage by 70% in some use cases.
+
+ To compile this driver as a module, choose M here: the module will be
+ called ep93xx_adc.
+
config EXYNOS_ADC
tristate "Exynos ADC driver support"
depends on ARCH_EXYNOS || ARCH_S3C24XX || ARCH_S3C64XX || (OF && COMPILE_TEST)
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 99b37a9..5481b42 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_AXP288_ADC) += axp288_adc.o
obj-$(CONFIG_BERLIN2_ADC) += berlin2-adc.o
obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
+obj-$(CONFIG_EP93XX_ADC) += ep93xx_adc.o
obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
obj-$(CONFIG_HI8435) += hi8435.o
obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
diff --git a/drivers/iio/adc/ep93xx_adc.c b/drivers/iio/adc/ep93xx_adc.c
new file mode 100644
index 0000000..ebaacb9
--- /dev/null
+++ b/drivers/iio/adc/ep93xx_adc.c
@@ -0,0 +1,253 @@
+/*
+ * Driver for ADC module on the Cirrus Logic EP93xx series of SoCs
+ *
+ * Copyright (C) 2015 Alexander Sverdlin
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * The driver uses polling to get the conversion status. According to EP93xx
+ * datasheets, reading ADCResult register starts the conversion, but user 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>
+
+#define EP93XX_NUM_CHANNELS 8
+
+#define ep93xx_adc_reg_read(reg) __raw_readl(reg)
+#define ep93xx_adc_reg_write(val, reg) __raw_writel(val, reg)
+
+/*
+ * 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 30% 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
+#define EP93XX_ADC_INT_EN 0x24
+#define EP93XX_ADC_RINTEN BIT(11)
+
+struct ep93xx_adc_priv {
+ struct clk *clk;
+ void __iomem *base;
+ int lastch;
+ struct mutex lock;
+};
+
+#define EP93XX_ADC_CH(index, dname, ename, swcfg) { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = index, \
+ .address = swcfg, \
+ .datasheet_name = dname, \
+ .extend_name = ename, \
+ .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 numering is
+ * not defined. So the last three are numbered randomly, let's say.
+ */
+static const struct iio_chan_spec ep93xx_adc_channels[EP93XX_NUM_CHANNELS] = {
+ EP93XX_ADC_CH(0, "YM", "ym", 0x608),
+ EP93XX_ADC_CH(1, "SXP", "sxp", 0x680),
+ EP93XX_ADC_CH(2, "SXM", "sxm", 0x640),
+ EP93XX_ADC_CH(3, "SYP", "syp", 0x620),
+ EP93XX_ADC_CH(4, "SYM", "sym", 0x610),
+ EP93XX_ADC_CH(5, "XP", "xp", 0x601),
+ EP93XX_ADC_CH(6, "XM", "xm", 0x602),
+ EP93XX_ADC_CH(7, "YP", "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);
+
+ 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();
+ ep93xx_adc_reg_write(0xAA,
+ priv->base + EP93XX_ADC_SW_LOCK);
+ ep93xx_adc_reg_write(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 */
+ ep93xx_adc_reg_read(priv->base + EP93XX_ADC_RESULT);
+ /* Ensure maximun 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... */
+ while (1) {
+ u32 t;
+
+ t = ep93xx_adc_reg_read(priv->base + EP93XX_ADC_RESULT);
+ if (t & EP93XX_ADC_SDR) {
+ /* Sign extend lower 16 bits */
+ *value = (s16)t;
+ break;
+ }
+ }
+ mutex_unlock(&priv->lock);
+ return IIO_VAL_INT;
+
+ 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 = {
+ .driver_module = THIS_MODULE,
+ .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;
+ struct resource *res;
+
+ iiodev = devm_iio_device_alloc(&pdev->dev,
+ sizeof(struct ep93xx_adc_priv));
+ if (!iiodev)
+ return -ENOMEM;
+ priv = iio_priv(iiodev);
+
+ priv->clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(priv->clk)) {
+ dev_err(&pdev->dev, "Cannot obtain clock");
+ return PTR_ERR(priv->clk);
+ }
+
+ pclk = clk_get_parent(priv->clk);
+ if (!pclk) {
+ dev_warn(&pdev->dev, "Cannot obtain parent clock");
+ } 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
+ * respectively 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");
+ /*
+ * We can tolerate rate setting failure because the module should
+ * work in any case.
+ */
+ }
+
+ ret = clk_enable(priv->clk);
+ if (ret) {
+ dev_err(&pdev->dev, "Cannot enable clock");
+ return ret;
+ }
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res) {
+ dev_err(&pdev->dev, "Cannot obtain memory resource");
+ return -ENXIO;
+ }
+ priv->base = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(priv->base)) {
+ dev_err(&pdev->dev, "Cannot map memory resource");
+ return PTR_ERR(priv->base);
+ }
+
+ iiodev->dev.parent = &pdev->dev;
+ 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);
+
+ ret = devm_iio_device_register(&pdev->dev, iiodev);
+ if (ret)
+ return ret;
+
+ platform_set_drvdata(pdev, iiodev);
+
+ return 0;
+}
+
+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);
+
+ clk_disable(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@xxxxxxxxx>");
+MODULE_DESCRIPTION("Cirrus Logic EP93XX ADC driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ep93xx-adc");
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