[PATCH v5 0/5] iio: ADC driver for EP93xx SoC

[PATCH v5 0/5] iio: ADC driver for EP93xx SoC

[Alexander Sverdlin]

This series prepares the necessary infrastructure for ADC platform device on
Cirrus Logic EP93xx family of SoCs and adds the driver for ADC device using
IIO subsystem.

Changelog
v5:
  Rebased to ea094f3c830a
  Added Ryan's ack
v4:
  Spelling improvements
  sign_extend32() usage
v3:
  Rebased to the current master
  sizeof(struct foo) -> sizeof(*bar)
v2:
  Added Documentation/iio/ep93xx_adc.txt
  Removed extend_name
  Added timeout to the status polling loop
  Used iio_device_register() instead of devm_iio_device_register()

Alexander Sverdlin (5):
  clk: ep93xx: Implement clk_get_parent()
  clk: ep93xx: Add ADC clock
  ep93xx: Add ADC platform device support to core
  edb93xx: Add ADC platform device
  iio: adc: New driver for Cirrus Logic EP93xx ADC

 Documentation/iio/ep93xx_adc.txt             |  29 +++
 arch/arm/mach-ep93xx/clock.c                 |  14 ++
 arch/arm/mach-ep93xx/core.c                  |  24 +++
 arch/arm/mach-ep93xx/edb93xx.c               |   1 +
 arch/arm/mach-ep93xx/include/mach/platform.h |   1 +
 arch/arm/mach-ep93xx/soc.h                   |   1 +
 drivers/iio/adc/Kconfig                      |  11 ++
 drivers/iio/adc/Makefile                     |   1 +
 drivers/iio/adc/ep93xx_adc.c                 | 255 +++++++++++++++++++++++++++
 9 files changed, 337 insertions(+)
 create mode 100644 Documentation/iio/ep93xx_adc.txt
 create mode 100644 drivers/iio/adc/ep93xx_adc.c

-- 
2.12.2

[PATCH v5 1/5] clk: ep93xx: Implement clk_get_parent()

[Alexander Sverdlin]

Trivial implementation of clk_get_parent(), but necessary for some drivers,
such as ADC.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: Ryan Mallon <rmallon@gmail.com>
---
 arch/arm/mach-ep93xx/clock.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/mach-ep93xx/clock.c b/arch/arm/mach-ep93xx/clock.c
index 39ef3b613912..b9cd9d7da14d 100644
--- a/arch/arm/mach-ep93xx/clock.c
+++ b/arch/arm/mach-ep93xx/clock.c
@@ -475,6 +475,12 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
 }
 EXPORT_SYMBOL(clk_set_rate);
 
+struct clk *clk_get_parent(struct clk *clk)
+{
+	return clk->parent;
+}
+EXPORT_SYMBOL(clk_get_parent);
+
 
 static char fclk_divisors[] = { 1, 2, 4, 8, 16, 1, 1, 1 };
 static char hclk_divisors[] = { 1, 2, 4, 5, 6, 8, 16, 32 };
-- 
2.12.2

[PATCH v5 2/5] clk: ep93xx: Add ADC clock

[Alexander Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@gmx.de>

ADC and keypad controller clocks share the same control register, so use the
existing infrastructure to add ADC clock support for Cirrus Logic EP93xx SoCs.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: Ryan Mallon <rmallon@gmail.com>
---
 arch/arm/mach-ep93xx/clock.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/mach-ep93xx/clock.c b/arch/arm/mach-ep93xx/clock.c
index b9cd9d7da14d..425342637e47 100644
--- a/arch/arm/mach-ep93xx/clock.c
+++ b/arch/arm/mach-ep93xx/clock.c
@@ -98,6 +98,13 @@ static struct clk clk_keypad = {
 	.enable_mask	= EP93XX_SYSCON_KEYTCHCLKDIV_KEN,
 	.set_rate	= set_keytchclk_rate,
 };
+static struct clk clk_adc = {
+	.parent		= &clk_xtali,
+	.sw_locked	= 1,
+	.enable_reg	= EP93XX_SYSCON_KEYTCHCLKDIV,
+	.enable_mask	= EP93XX_SYSCON_KEYTCHCLKDIV_TSEN,
+	.set_rate	= set_keytchclk_rate,
+};
 static struct clk clk_spi = {
 	.parent		= &clk_xtali,
 	.rate		= EP93XX_EXT_CLK_RATE,
@@ -214,6 +221,7 @@ static struct clk_lookup clocks[] = {
 	INIT_CK(NULL,			"pll2",		&clk_pll2),
 	INIT_CK("ohci-platform",	NULL,		&clk_usb_host),
 	INIT_CK("ep93xx-keypad",	NULL,		&clk_keypad),
+	INIT_CK("ep93xx-adc",		NULL,		&clk_adc),
 	INIT_CK("ep93xx-fb",		NULL,		&clk_video),
 	INIT_CK("ep93xx-spi.0",		NULL,		&clk_spi),
 	INIT_CK("ep93xx-i2s",		"mclk",		&clk_i2s_mclk),
-- 
2.12.2

[PATCH v5 3/5] ep93xx: Add ADC platform device support to core

[Alexander Sverdlin]

Newly provided ep93xx_register_adc() could be used by machine-specific code
to create ADC platform device on Cirrus Logic EP93xx SoC-based machines.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: Ryan Mallon <rmallon@gmail.com>
---
 arch/arm/mach-ep93xx/core.c                  | 24 ++++++++++++++++++++++++
 arch/arm/mach-ep93xx/include/mach/platform.h |  1 +
 arch/arm/mach-ep93xx/soc.h                   |  1 +
 3 files changed, 26 insertions(+)

diff --git a/arch/arm/mach-ep93xx/core.c b/arch/arm/mach-ep93xx/core.c
index c393b1b0310d..f53c61813998 100644
--- a/arch/arm/mach-ep93xx/core.c
+++ b/arch/arm/mach-ep93xx/core.c
@@ -821,6 +821,30 @@ void ep93xx_ide_release_gpio(struct platform_device *pdev)
 EXPORT_SYMBOL(ep93xx_ide_release_gpio);
 
 /*************************************************************************
+ * EP93xx ADC
+ *************************************************************************/
+static struct resource ep93xx_adc_resources[] = {
+	DEFINE_RES_MEM(EP93XX_ADC_PHYS_BASE, 0x28),
+	DEFINE_RES_IRQ(IRQ_EP93XX_TOUCH),
+};
+
+static struct platform_device ep93xx_adc_device = {
+	.name		= "ep93xx-adc",
+	.id		= -1,
+	.num_resources	= ARRAY_SIZE(ep93xx_adc_resources),
+	.resource	= ep93xx_adc_resources,
+};
+
+void __init ep93xx_register_adc(void)
+{
+	/* Power up ADC, deactivate Touch Screen Controller */
+	ep93xx_devcfg_set_clear(EP93XX_SYSCON_DEVCFG_TIN,
+				EP93XX_SYSCON_DEVCFG_ADCPD);
+
+	platform_device_register(&ep93xx_adc_device);
+}
+
+/*************************************************************************
  * EP93xx Security peripheral
  *************************************************************************/
 
diff --git a/arch/arm/mach-ep93xx/include/mach/platform.h b/arch/arm/mach-ep93xx/include/mach/platform.h
index 4c0bbd97f741..db0839691ef5 100644
--- a/arch/arm/mach-ep93xx/include/mach/platform.h
+++ b/arch/arm/mach-ep93xx/include/mach/platform.h
@@ -52,6 +52,7 @@ int ep93xx_i2s_acquire(void);
 void ep93xx_i2s_release(void);
 void ep93xx_register_ac97(void);
 void ep93xx_register_ide(void);
+void ep93xx_register_adc(void);
 int ep93xx_ide_acquire_gpio(struct platform_device *pdev);
 void ep93xx_ide_release_gpio(struct platform_device *pdev);
 
diff --git a/arch/arm/mach-ep93xx/soc.h b/arch/arm/mach-ep93xx/soc.h
index 7bf7ff8beae7..d20e631164cf 100644
--- a/arch/arm/mach-ep93xx/soc.h
+++ b/arch/arm/mach-ep93xx/soc.h
@@ -95,6 +95,7 @@
 #define EP93XX_KEY_MATRIX_PHYS_BASE	EP93XX_APB_PHYS(0x000f0000)
 #define EP93XX_KEY_MATRIX_BASE		EP93XX_APB_IOMEM(0x000f0000)
 
+#define EP93XX_ADC_PHYS_BASE		EP93XX_APB_PHYS(0x00100000)
 #define EP93XX_ADC_BASE			EP93XX_APB_IOMEM(0x00100000)
 #define EP93XX_TOUCHSCREEN_BASE		EP93XX_APB_IOMEM(0x00100000)
 
-- 
2.12.2

[PATCH v5 4/5] edb93xx: Add ADC platform device

[Alexander Sverdlin]

This enables the creation of ADC platform device on EDB93xx series of Cirrus
Logic evaluation boards. The driver for this device must be enabled separately,
either as built-in, or a module.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: Ryan Mallon <rmallon@gmail.com>
---
 arch/arm/mach-ep93xx/edb93xx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/mach-ep93xx/edb93xx.c b/arch/arm/mach-ep93xx/edb93xx.c
index 0ac176386789..7a7f280b07d7 100644
--- a/arch/arm/mach-ep93xx/edb93xx.c
+++ b/arch/arm/mach-ep93xx/edb93xx.c
@@ -245,6 +245,7 @@ static void __init edb93xx_init_machine(void)
 	edb93xx_register_pwm();
 	edb93xx_register_fb();
 	edb93xx_register_ide();
+	ep93xx_register_adc();
 }
 
 
-- 
2.12.2

[PATCH v5 5/5] iio: adc: New driver for Cirrus Logic EP93xx ADC

[Alexander Sverdlin]

New driver adding support for ADC found on Cirrus Logic EP93xx series of SoCs.
Board specific code must take care to create plaform device with all necessary
resources.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
---
 Documentation/iio/ep93xx_adc.txt |  29 +++++
 drivers/iio/adc/Kconfig          |  11 ++
 drivers/iio/adc/Makefile         |   1 +
 drivers/iio/adc/ep93xx_adc.c     | 255 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 296 insertions(+)
 create mode 100644 Documentation/iio/ep93xx_adc.txt
 create mode 100644 drivers/iio/adc/ep93xx_adc.c

diff --git a/Documentation/iio/ep93xx_adc.txt b/Documentation/iio/ep93xx_adc.txt
new file mode 100644
index 000000000000..23053e7817bd
--- /dev/null
+++ b/Documentation/iio/ep93xx_adc.txt
@@ -0,0 +1,29 @@
+Cirrus Logic EP93xx ADC driver.
+
+1. Overview
+
+The driver is intended to work on both low-end (EP9301, EP9302) devices with
+5-channel ADC and high-end (EP9307, EP9312, EP9315) devices with 10-channel
+touchscreen/ADC module.
+
+2. Channel numbering
+
+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.
+
+Assuming ep93xx_adc is IIO device0, you'd find the following entries under
+/sys/bus/iio/devices/iio:device0/:
+
+  +-----------------+---------------+
+  | sysfs entry     | ball/pin name |
+  +-----------------+---------------+
+  | in_voltage0_raw | YM            |
+  | in_voltage1_raw | SXP           |
+  | in_voltage2_raw | SXM           |
+  | in_voltage3_raw | SYP           |
+  | in_voltage4_raw | SYM           |
+  | in_voltage5_raw | XP            |
+  | in_voltage6_raw | XM            |
+  | in_voltage7_raw | YP            |
+  +-----------------+---------------+
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 401f47b51d83..a3eba810292a 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -249,6 +249,17 @@ config ENVELOPE_DETECTOR
 	  To compile this driver as a module, choose M here: the module will be
 	  called envelope-detector.
 
+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 90% 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 9339bec4babe..d1a036d38486 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
 obj-$(CONFIG_CPCAP_ADC) += cpcap-adc.o
 obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
 obj-$(CONFIG_ENVELOPE_DETECTOR) += envelope-detector.o
+obj-$(CONFIG_EP93XX_ADC) += ep93xx_adc.o
 obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
 obj-$(CONFIG_FSL_MX25_ADC) += fsl-imx25-gcq.o
 obj-$(CONFIG_HI8435) += hi8435.o
diff --git a/drivers/iio/adc/ep93xx_adc.c b/drivers/iio/adc/ep93xx_adc.c
new file mode 100644
index 000000000000..a179ac476c6d
--- /dev/null
+++ b/drivers/iio/adc/ep93xx_adc.c
@@ -0,0 +1,255 @@
+/*
+ * 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 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 = {
+	.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(*priv));
+	if (!iiodev)
+		return -ENOMEM;
+	priv = iio_priv(iiodev);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "Cannot obtain memory resource\n");
+		return -ENXIO;
+	}
+	priv->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->base)) {
+		dev_err(&pdev->dev, "Cannot map memory resource\n");
+		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);
+
+	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_enable(priv->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "Cannot enable clock\n");
+		return ret;
+	}
+
+	ret = iio_device_register(iiodev);
+	if (ret)
+		clk_disable(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(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");
-- 
2.12.2

[PATCH v5 5/5] iio: adc: New driver for Cirrus Logic EP93xx ADC

[Jonathan Cameron]

On Sun,  4 Jun 2017 01:26:52 +0200
Alexander Sverdlin <alexander.sverdlin@gmail.com> wrote:

> New driver adding support for ADC found on Cirrus Logic EP93xx series of SoCs.
> Board specific code must take care to create plaform device with all necessary
> resources.
> 
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
> Acked-by: Jonathan Cameron <jic23@kernel.org>
Ah, I'd already acked ;)

Anyhow, one note inline about the effects of an upcoming subsystem wide change.
Right now this is correct, but I forget it's taking a different path and try
to do that series in one go, we'll get build breakage.

Jonathan
> ---
>  Documentation/iio/ep93xx_adc.txt |  29 +++++
>  drivers/iio/adc/Kconfig          |  11 ++
>  drivers/iio/adc/Makefile         |   1 +
>  drivers/iio/adc/ep93xx_adc.c     | 255 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 296 insertions(+)
>  create mode 100644 Documentation/iio/ep93xx_adc.txt
>  create mode 100644 drivers/iio/adc/ep93xx_adc.c
> 
> diff --git a/Documentation/iio/ep93xx_adc.txt b/Documentation/iio/ep93xx_adc.txt
> new file mode 100644
> index 000000000000..23053e7817bd
> --- /dev/null
> +++ b/Documentation/iio/ep93xx_adc.txt
> @@ -0,0 +1,29 @@
> +Cirrus Logic EP93xx ADC driver.
> +
> +1. Overview
> +
> +The driver is intended to work on both low-end (EP9301, EP9302) devices with
> +5-channel ADC and high-end (EP9307, EP9312, EP9315) devices with 10-channel
> +touchscreen/ADC module.
> +
> +2. Channel numbering
> +
> +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.
> +
> +Assuming ep93xx_adc is IIO device0, you'd find the following entries under
> +/sys/bus/iio/devices/iio:device0/:
> +
> +  +-----------------+---------------+
> +  | sysfs entry     | ball/pin name |
> +  +-----------------+---------------+
> +  | in_voltage0_raw | YM            |
> +  | in_voltage1_raw | SXP           |
> +  | in_voltage2_raw | SXM           |
> +  | in_voltage3_raw | SYP           |
> +  | in_voltage4_raw | SYM           |
> +  | in_voltage5_raw | XP            |
> +  | in_voltage6_raw | XM            |
> +  | in_voltage7_raw | YP            |
> +  +-----------------+---------------+
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 401f47b51d83..a3eba810292a 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -249,6 +249,17 @@ config ENVELOPE_DETECTOR
>  	  To compile this driver as a module, choose M here: the module will be
>  	  called envelope-detector.
>  
> +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 90% 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 9339bec4babe..d1a036d38486 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -25,6 +25,7 @@ obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
>  obj-$(CONFIG_CPCAP_ADC) += cpcap-adc.o
>  obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
>  obj-$(CONFIG_ENVELOPE_DETECTOR) += envelope-detector.o
> +obj-$(CONFIG_EP93XX_ADC) += ep93xx_adc.o
>  obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
>  obj-$(CONFIG_FSL_MX25_ADC) += fsl-imx25-gcq.o
>  obj-$(CONFIG_HI8435) += hi8435.o
> diff --git a/drivers/iio/adc/ep93xx_adc.c b/drivers/iio/adc/ep93xx_adc.c
> new file mode 100644
> index 000000000000..a179ac476c6d
> --- /dev/null
> +++ b/drivers/iio/adc/ep93xx_adc.c
> @@ -0,0 +1,255 @@
> +/*
> + * 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 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 = {
> +	.driver_module = THIS_MODULE,
Just to note, we have a series under review which will
get rid of this.  I'll try to remember this one might
be going through a different tree. Hopefully the build
tests will pick it up if I'm in a forgetful mood!

Jonathan

> +	.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(*priv));
> +	if (!iiodev)
> +		return -ENOMEM;
> +	priv = iio_priv(iiodev);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(&pdev->dev, "Cannot obtain memory resource\n");
> +		return -ENXIO;
> +	}
> +	priv->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(priv->base)) {
> +		dev_err(&pdev->dev, "Cannot map memory resource\n");
> +		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);
> +
> +	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_enable(priv->clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Cannot enable clock\n");
> +		return ret;
> +	}
> +
> +	ret = iio_device_register(iiodev);
> +	if (ret)
> +		clk_disable(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(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");

[PATCH v5 0/5] iio: ADC driver for EP93xx SoC

[Jonathan Cameron]

On Sun,  4 Jun 2017 01:26:47 +0200
Alexander Sverdlin <alexander.sverdlin@gmail.com> wrote:

> This series prepares the necessary infrastructure for ADC platform device on
> Cirrus Logic EP93xx family of SoCs and adds the driver for ADC device using
> IIO subsystem.
The reason these have been reposted is because the EP93xx don't
have an actual tree as such.  They are typically handled
directly through the arm-soc tree.

As such I'm looking for a route to get this applied.
The dependencies are such that the whole series should go through
either arm-soc or iio.  I don't really mind which.
Either I need Acks for applying the patches that touch
the arch bits (we have Ryan's but I'd like a more general
arm-soc one given this will be in your area), or
I will probably ack the driver in a minute so the log can
go through arm-soc.

Anyhow, don't really mind but let's get this moving!

Jonathan
> 
> Changelog
> v5:
>   Rebased to ea094f3c830a
>   Added Ryan's ack
> v4:
>   Spelling improvements
>   sign_extend32() usage
> v3:
>   Rebased to the current master
>   sizeof(struct foo) -> sizeof(*bar)
> v2:
>   Added Documentation/iio/ep93xx_adc.txt
>   Removed extend_name
>   Added timeout to the status polling loop
>   Used iio_device_register() instead of devm_iio_device_register()
> 
> Alexander Sverdlin (5):
>   clk: ep93xx: Implement clk_get_parent()
>   clk: ep93xx: Add ADC clock
>   ep93xx: Add ADC platform device support to core
>   edb93xx: Add ADC platform device
>   iio: adc: New driver for Cirrus Logic EP93xx ADC
> 
>  Documentation/iio/ep93xx_adc.txt             |  29 +++
>  arch/arm/mach-ep93xx/clock.c                 |  14 ++
>  arch/arm/mach-ep93xx/core.c                  |  24 +++
>  arch/arm/mach-ep93xx/edb93xx.c               |   1 +
>  arch/arm/mach-ep93xx/include/mach/platform.h |   1 +
>  arch/arm/mach-ep93xx/soc.h                   |   1 +
>  drivers/iio/adc/Kconfig                      |  11 ++
>  drivers/iio/adc/Makefile                     |   1 +
>  drivers/iio/adc/ep93xx_adc.c                 | 255 +++++++++++++++++++++++++++
>  9 files changed, 337 insertions(+)
>  create mode 100644 Documentation/iio/ep93xx_adc.txt
>  create mode 100644 drivers/iio/adc/ep93xx_adc.c
> 

[PATCH v5 0/5] iio: ADC driver for EP93xx SoC

[Arnd Bergmann]

On Sun, Jun 11, 2017 at 4:18 PM, Jonathan Cameron <jic23@kernel.org> wrote:
> On Sun,  4 Jun 2017 01:26:47 +0200
> Alexander Sverdlin <alexander.sverdlin@gmail.com> wrote:
>
>> This series prepares the necessary infrastructure for ADC platform device on
>> Cirrus Logic EP93xx family of SoCs and adds the driver for ADC device using
>> IIO subsystem.
> The reason these have been reposted is because the EP93xx don't
> have an actual tree as such.  They are typically handled
> directly through the arm-soc tree.
>
> As such I'm looking for a route to get this applied.
> The dependencies are such that the whole series should go through
> either arm-soc or iio.  I don't really mind which.
> Either I need Acks for applying the patches that touch
> the arch bits (we have Ryan's but I'd like a more general
> arm-soc one given this will be in your area), or
> I will probably ack the driver in a minute so the log can
> go through arm-soc.
>
> Anyhow, don't really mind but let's get this moving!

Alexander just pointed me to the series, I had missed it earlier.

The patches for arch/arm/mach-ep93xx look reasonable to me,
with one minor complaint: please use "ARM:" as the subject prefix.

Alexander, can you send a pull request for the first four patches
to arm at kernel.org, or a set of patches if that is easier for you?

I think the adc driver can just get merged through the iio tree,
as there is no strict build-time dependency. I realize the driver
will fail to link when built on ep93xx or another platform that lacks
the clk_get_parent() implementation, but I think that's ok since
we have an old bug in several platforms concerning this, and
I have proposed a fix for it already.

       Arnd

[PATCH v6] iio: adc: New driver for Cirrus Logic EP93xx ADC

[Alexander Sverdlin]

New driver adding support for ADC found on Cirrus Logic EP93xx series of SoCs.
Board specific code must take care to create plaform device with all necessary
resources.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
---
Changelog
v6:
  Separated from mach-ep93xx/ patches (will come via arm-soc tree)
  Rebased to v4.13-rc2
v5:
  Rebased to ea094f3c830a
v4:
  Spelling improvements
  sign_extend32() usage
v3:
  Rebased to the current master
  sizeof(struct foo) -> sizeof(*bar)
v2:
  Added Documentation/iio/ep93xx_adc.txt
  Removed extend_name
  Added timeout to the status polling loop
  Used iio_device_register() instead of devm_iio_device_register()

Diffstat
 Documentation/iio/ep93xx_adc.txt |  29 +++++
 drivers/iio/adc/Kconfig          |  11 ++
 drivers/iio/adc/Makefile         |   1 +
 drivers/iio/adc/ep93xx_adc.c     | 255 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 296 insertions(+)
 create mode 100644 Documentation/iio/ep93xx_adc.txt
 create mode 100644 drivers/iio/adc/ep93xx_adc.c

diff --git a/Documentation/iio/ep93xx_adc.txt b/Documentation/iio/ep93xx_adc.txt
new file mode 100644
index 000000000000..23053e7817bd
--- /dev/null
+++ b/Documentation/iio/ep93xx_adc.txt
@@ -0,0 +1,29 @@
+Cirrus Logic EP93xx ADC driver.
+
+1. Overview
+
+The driver is intended to work on both low-end (EP9301, EP9302) devices with
+5-channel ADC and high-end (EP9307, EP9312, EP9315) devices with 10-channel
+touchscreen/ADC module.
+
+2. Channel numbering
+
+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.
+
+Assuming ep93xx_adc is IIO device0, you'd find the following entries under
+/sys/bus/iio/devices/iio:device0/:
+
+  +-----------------+---------------+
+  | sysfs entry     | ball/pin name |
+  +-----------------+---------------+
+  | in_voltage0_raw | YM            |
+  | in_voltage1_raw | SXP           |
+  | in_voltage2_raw | SXM           |
+  | in_voltage3_raw | SYP           |
+  | in_voltage4_raw | SYM           |
+  | in_voltage5_raw | XP            |
+  | in_voltage6_raw | XM            |
+  | in_voltage7_raw | YP            |
+  +-----------------+---------------+
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 614fa41559b1..5c1ab02ef730 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -249,6 +249,17 @@ config ENVELOPE_DETECTOR
 	  To compile this driver as a module, choose M here: the module will be
 	  called envelope-detector.
 
+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 90% 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 b546736a5541..2d266eaf352c 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
 obj-$(CONFIG_CPCAP_ADC) += cpcap-adc.o
 obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
 obj-$(CONFIG_ENVELOPE_DETECTOR) += envelope-detector.o
+obj-$(CONFIG_EP93XX_ADC) += ep93xx_adc.o
 obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
 obj-$(CONFIG_FSL_MX25_ADC) += fsl-imx25-gcq.o
 obj-$(CONFIG_HI8435) += hi8435.o
diff --git a/drivers/iio/adc/ep93xx_adc.c b/drivers/iio/adc/ep93xx_adc.c
new file mode 100644
index 000000000000..a179ac476c6d
--- /dev/null
+++ b/drivers/iio/adc/ep93xx_adc.c
@@ -0,0 +1,255 @@
+/*
+ * 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 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 = {
+	.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(*priv));
+	if (!iiodev)
+		return -ENOMEM;
+	priv = iio_priv(iiodev);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "Cannot obtain memory resource\n");
+		return -ENXIO;
+	}
+	priv->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->base)) {
+		dev_err(&pdev->dev, "Cannot map memory resource\n");
+		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);
+
+	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_enable(priv->clk);
+	if (ret) {
+		dev_err(&pdev->dev, "Cannot enable clock\n");
+		return ret;
+	}
+
+	ret = iio_device_register(iiodev);
+	if (ret)
+		clk_disable(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(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");
-- 
2.13.2