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Subject[PATCH v2 8/8] iio: counter: Add support for STM32 LPTimer
Date
Add support for STM32 Low-Power Timer, that can be used as counter
or quadrature encoder.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
Changes in v2:
- s/Low Power/Low-Power
- update few comments
---
.../ABI/testing/sysfs-bus-iio-lptimer-stm32 | 57 +++
drivers/iio/counter/Kconfig | 9 +
drivers/iio/counter/Makefile | 1 +
drivers/iio/counter/stm32-lptimer-cnt.c | 383 +++++++++++++++++++++
4 files changed, 450 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-lptimer-stm32
create mode 100644 drivers/iio/counter/stm32-lptimer-cnt.c

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-lptimer-stm32 b/Documentation/ABI/testing/sysfs-bus-iio-lptimer-stm32
new file mode 100644
index 0000000..ad2cc63
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-lptimer-stm32
@@ -0,0 +1,57 @@
+What: /sys/bus/iio/devices/iio:deviceX/in_count0_preset
+KernelVersion: 4.13
+Contact: fabrice.gasnier@st.com
+Description:
+ Reading returns the current preset value. Writing sets the
+ preset value. Encoder counts continuously from 0 to preset
+ value, depending on direction (up/down).
+
+What: /sys/bus/iio/devices/iio:deviceX/in_count_quadrature_mode_available
+KernelVersion: 4.13
+Contact: fabrice.gasnier@st.com
+Description:
+ Reading returns the list possible quadrature modes.
+
+What: /sys/bus/iio/devices/iio:deviceX/in_count0_quadrature_mode
+KernelVersion: 4.13
+Contact: fabrice.gasnier@st.com
+Description:
+ Configure the device counter quadrature modes:
+ - non-quadrature:
+ Encoder IN1 input servers as the count input (up
+ direction).
+ - quadrature:
+ Encoder IN1 and IN2 inputs are mixed to get direction
+ and count.
+
+What: /sys/bus/iio/devices/iio:deviceX/in_count_polarity_available
+KernelVersion: 4.13
+Contact: fabrice.gasnier@st.com
+Description:
+ Reading returns the list possible active edges.
+
+What: /sys/bus/iio/devices/iio:deviceX/in_count0_polarity
+KernelVersion: 4.13
+Contact: fabrice.gasnier@st.com
+Description:
+ Configure the device encoder/counter active edge:
+ - rising-edge
+ - falling-edge
+ - both-edges
+
+ In non-quadrature mode, device counts up on active edge.
+ In quadrature mode, encoder counting scenarios are as follows:
+ ----------------------------------------------------------------
+ | Active | Level on | IN1 signal | IN2 signal |
+ | edge | opposite |------------------------------------------
+ | | signal | Rising | Falling | Rising | Falling |
+ ----------------------------------------------------------------
+ | Rising | High -> | Down | - | Up | - |
+ | edge | Low -> | Up | - | Down | - |
+ ----------------------------------------------------------------
+ | Falling | High -> | - | Up | - | Down |
+ | edge | Low -> | - | Down | - | Up |
+ ----------------------------------------------------------------
+ | Both | High -> | Down | Up | Up | Down |
+ | edges | Low -> | Up | Down | Down | Up |
+ ----------------------------------------------------------------
diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
index b37e5fc..474e1ac 100644
--- a/drivers/iio/counter/Kconfig
+++ b/drivers/iio/counter/Kconfig
@@ -21,4 +21,13 @@ config 104_QUAD_8
The base port addresses for the devices may be configured via the base
array module parameter.

+config STM32_LPTIMER_CNT
+ tristate "STM32 LP Timer encoder counter driver"
+ depends on MFD_STM32_LPTIMER || COMPILE_TEST
+ help
+ Select this option to enable STM32 Low-Power Timer quadrature encoder
+ and counter driver.
+
+ To compile this driver as a module, choose M here: the
+ module will be called stm32-lptimer-cnt.
endmenu
diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
index 007e884..1b9a896 100644
--- a/drivers/iio/counter/Makefile
+++ b/drivers/iio/counter/Makefile
@@ -5,3 +5,4 @@
# When adding new entries keep the list in alphabetical order

obj-$(CONFIG_104_QUAD_8) += 104-quad-8.o
+obj-$(CONFIG_STM32_LPTIMER_CNT) += stm32-lptimer-cnt.o
diff --git a/drivers/iio/counter/stm32-lptimer-cnt.c b/drivers/iio/counter/stm32-lptimer-cnt.c
new file mode 100644
index 0000000..1c5909b
--- /dev/null
+++ b/drivers/iio/counter/stm32-lptimer-cnt.c
@@ -0,0 +1,383 @@
+/*
+ * STM32 Low-Power Timer Encoder and Counter driver
+ *
+ * Copyright (C) STMicroelectronics 2017
+ *
+ * Author: Fabrice Gasnier <fabrice.gasnier@st.com>
+ *
+ * Inspired by 104-quad-8 and stm32-timer-trigger drivers.
+ *
+ * License terms: GNU General Public License (GPL), version 2
+ */
+
+#include <linux/bitfield.h>
+#include <linux/iio/iio.h>
+#include <linux/mfd/stm32-lptimer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+struct stm32_lptim_cnt {
+ struct device *dev;
+ struct regmap *regmap;
+ struct clk *clk;
+ u32 preset;
+ u32 polarity;
+ u32 quadrature_mode;
+};
+
+static int stm32_lptim_is_enabled(struct stm32_lptim_cnt *priv)
+{
+ u32 val;
+ int ret;
+
+ ret = regmap_read(priv->regmap, STM32_LPTIM_CR, &val);
+ if (ret)
+ return ret;
+
+ return FIELD_GET(STM32_LPTIM_ENABLE, val);
+}
+
+static int stm32_lptim_set_enable_state(struct stm32_lptim_cnt *priv,
+ int enable)
+{
+ int ret;
+ u32 val;
+
+ val = FIELD_PREP(STM32_LPTIM_ENABLE, enable);
+ ret = regmap_write(priv->regmap, STM32_LPTIM_CR, val);
+ if (ret)
+ return ret;
+
+ if (!enable) {
+ clk_disable(priv->clk);
+ return 0;
+ }
+
+ /* LP timer must be enabled before writing CMP & ARR */
+ ret = regmap_write(priv->regmap, STM32_LPTIM_ARR, priv->preset);
+ if (ret)
+ return ret;
+
+ ret = regmap_write(priv->regmap, STM32_LPTIM_CMP, 0);
+ if (ret)
+ return ret;
+
+ /* ensure CMP & ARR registers are properly written */
+ ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
+ (val & STM32_LPTIM_CMPOK_ARROK),
+ 100, 1000);
+ if (ret)
+ return ret;
+
+ ret = regmap_write(priv->regmap, STM32_LPTIM_ICR,
+ STM32_LPTIM_CMPOKCF_ARROKCF);
+ if (ret)
+ return ret;
+
+ ret = clk_enable(priv->clk);
+ if (ret) {
+ regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
+ return ret;
+ }
+
+ /* Start LP timer in continuous mode */
+ return regmap_update_bits(priv->regmap, STM32_LPTIM_CR,
+ STM32_LPTIM_CNTSTRT, STM32_LPTIM_CNTSTRT);
+}
+
+static int stm32_lptim_setup(struct stm32_lptim_cnt *priv, int enable)
+{
+ u32 mask = STM32_LPTIM_ENC | STM32_LPTIM_COUNTMODE |
+ STM32_LPTIM_CKPOL | STM32_LPTIM_PRESC;
+ u32 val;
+
+ /* Setup LP timer encoder/counter and polarity, without prescaler */
+ if (priv->quadrature_mode)
+ val = enable ? STM32_LPTIM_ENC : 0;
+ else
+ val = enable ? STM32_LPTIM_COUNTMODE : 0;
+ val |= FIELD_PREP(STM32_LPTIM_CKPOL, enable ? priv->polarity : 0);
+
+ return regmap_update_bits(priv->regmap, STM32_LPTIM_CFGR, mask, val);
+}
+
+static int stm32_lptim_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_ENABLE:
+ if (val < 0 || val > 1)
+ return -EINVAL;
+
+ /* Check nobody uses the timer, or already disabled/enabled */
+ ret = stm32_lptim_is_enabled(priv);
+ if ((ret < 0) || (!ret && !val))
+ return ret;
+ if (val && ret)
+ return -EBUSY;
+
+ ret = stm32_lptim_setup(priv, val);
+ if (ret)
+ return ret;
+ return stm32_lptim_set_enable_state(priv, val);
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static int stm32_lptim_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+ u32 dat;
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ ret = regmap_read(priv->regmap, STM32_LPTIM_CNT, &dat);
+ if (ret)
+ return ret;
+ *val = dat;
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_ENABLE:
+ ret = stm32_lptim_is_enabled(priv);
+ if (ret < 0)
+ return ret;
+ *val = ret;
+ return IIO_VAL_INT;
+
+ case IIO_CHAN_INFO_SCALE:
+ /* Non-quadrature mode: scale = 1 */
+ *val = 1;
+ *val2 = 0;
+ if (priv->quadrature_mode) {
+ /*
+ * Quadrature encoder mode:
+ * - both edges, quarter cycle, scale is 0.25
+ * - either rising/falling edge scale is 0.5
+ */
+ if (priv->polarity > 1)
+ *val2 = 2;
+ else
+ *val2 = 1;
+ }
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct iio_info stm32_lptim_cnt_iio_info = {
+ .read_raw = stm32_lptim_read_raw,
+ .write_raw = stm32_lptim_write_raw,
+ .driver_module = THIS_MODULE,
+};
+
+static const char *const stm32_lptim_quadrature_modes[] = {
+ "non-quadrature",
+ "quadrature",
+};
+
+static int stm32_lptim_get_quadrature_mode(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+ return priv->quadrature_mode;
+}
+
+static int stm32_lptim_set_quadrature_mode(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ unsigned int type)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+ if (stm32_lptim_is_enabled(priv))
+ return -EBUSY;
+
+ priv->quadrature_mode = type;
+
+ return 0;
+}
+
+static const struct iio_enum stm32_lptim_quadrature_mode_en = {
+ .items = stm32_lptim_quadrature_modes,
+ .num_items = ARRAY_SIZE(stm32_lptim_quadrature_modes),
+ .get = stm32_lptim_get_quadrature_mode,
+ .set = stm32_lptim_set_quadrature_mode,
+};
+
+static const char * const stm32_lptim_cnt_polarity[] = {
+ "rising-edge", "falling-edge", "both-edges",
+};
+
+static int stm32_lptim_cnt_get_polarity(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+ return priv->polarity;
+}
+
+static int stm32_lptim_cnt_set_polarity(struct iio_dev *indio_dev,
+ const struct iio_chan_spec *chan,
+ unsigned int type)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+ if (stm32_lptim_is_enabled(priv))
+ return -EBUSY;
+
+ priv->polarity = type;
+
+ return 0;
+}
+
+static const struct iio_enum stm32_lptim_cnt_polarity_en = {
+ .items = stm32_lptim_cnt_polarity,
+ .num_items = ARRAY_SIZE(stm32_lptim_cnt_polarity),
+ .get = stm32_lptim_cnt_get_polarity,
+ .set = stm32_lptim_cnt_set_polarity,
+};
+
+static ssize_t stm32_lptim_cnt_get_preset(struct iio_dev *indio_dev,
+ uintptr_t private,
+ const struct iio_chan_spec *chan,
+ char *buf)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+
+ return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset);
+}
+
+static ssize_t stm32_lptim_cnt_set_preset(struct iio_dev *indio_dev,
+ uintptr_t private,
+ const struct iio_chan_spec *chan,
+ const char *buf, size_t len)
+{
+ struct stm32_lptim_cnt *priv = iio_priv(indio_dev);
+ int ret;
+
+ if (stm32_lptim_is_enabled(priv))
+ return -EBUSY;
+
+ ret = kstrtouint(buf, 0, &priv->preset);
+ if (ret)
+ return ret;
+
+ if (priv->preset > STM32_LPTIM_MAX_ARR)
+ return -EINVAL;
+
+ return len;
+}
+
+/* LP timer with encoder */
+static const struct iio_chan_spec_ext_info stm32_lptim_enc_ext_info[] = {
+ {
+ .name = "preset",
+ .shared = IIO_SEPARATE,
+ .read = stm32_lptim_cnt_get_preset,
+ .write = stm32_lptim_cnt_set_preset,
+ },
+ IIO_ENUM("polarity", IIO_SEPARATE, &stm32_lptim_cnt_polarity_en),
+ IIO_ENUM_AVAILABLE("polarity", &stm32_lptim_cnt_polarity_en),
+ IIO_ENUM("quadrature_mode", IIO_SEPARATE,
+ &stm32_lptim_quadrature_mode_en),
+ IIO_ENUM_AVAILABLE("quadrature_mode", &stm32_lptim_quadrature_mode_en),
+ {}
+};
+
+static const struct iio_chan_spec stm32_lptim_enc_channels = {
+ .type = IIO_COUNT,
+ .channel = 0,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_ENABLE) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ .ext_info = stm32_lptim_enc_ext_info,
+ .indexed = 1,
+};
+
+/* LP timer without encoder (counter only) */
+static const struct iio_chan_spec_ext_info stm32_lptim_cnt_ext_info[] = {
+ {
+ .name = "preset",
+ .shared = IIO_SEPARATE,
+ .read = stm32_lptim_cnt_get_preset,
+ .write = stm32_lptim_cnt_set_preset,
+ },
+ IIO_ENUM("polarity", IIO_SEPARATE, &stm32_lptim_cnt_polarity_en),
+ IIO_ENUM_AVAILABLE("polarity", &stm32_lptim_cnt_polarity_en),
+ {}
+};
+
+static const struct iio_chan_spec stm32_lptim_cnt_channels = {
+ .type = IIO_COUNT,
+ .channel = 0,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_ENABLE) |
+ BIT(IIO_CHAN_INFO_SCALE),
+ .ext_info = stm32_lptim_cnt_ext_info,
+ .indexed = 1,
+};
+
+static int stm32_lptim_cnt_probe(struct platform_device *pdev)
+{
+ struct stm32_lptimer *ddata = dev_get_drvdata(pdev->dev.parent);
+ struct stm32_lptim_cnt *priv;
+ struct iio_dev *indio_dev;
+
+ if (IS_ERR_OR_NULL(ddata))
+ return -EINVAL;
+
+ indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ priv = iio_priv(indio_dev);
+ priv->dev = &pdev->dev;
+ priv->regmap = ddata->regmap;
+ priv->clk = ddata->clk;
+ priv->preset = STM32_LPTIM_MAX_ARR;
+
+ indio_dev->name = dev_name(&pdev->dev);
+ indio_dev->dev.parent = &pdev->dev;
+ indio_dev->dev.of_node = pdev->dev.of_node;
+ indio_dev->info = &stm32_lptim_cnt_iio_info;
+ if (ddata->has_encoder)
+ indio_dev->channels = &stm32_lptim_enc_channels;
+ else
+ indio_dev->channels = &stm32_lptim_cnt_channels;
+ indio_dev->num_channels = 1;
+
+ platform_set_drvdata(pdev, priv);
+
+ return devm_iio_device_register(&pdev->dev, indio_dev);
+}
+
+static const struct of_device_id stm32_lptim_cnt_of_match[] = {
+ { .compatible = "st,stm32-lptimer-counter", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, stm32_lptim_cnt_of_match);
+
+static struct platform_driver stm32_lptim_cnt_driver = {
+ .probe = stm32_lptim_cnt_probe,
+ .driver = {
+ .name = "stm32-lptimer-counter",
+ .of_match_table = stm32_lptim_cnt_of_match,
+ },
+};
+module_platform_driver(stm32_lptim_cnt_driver);
+
+MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
+MODULE_ALIAS("platform:stm32-lptimer-counter");
+MODULE_DESCRIPTION("STMicroelectronics STM32 LPTIM counter driver");
+MODULE_LICENSE("GPL v2");
--
1.9.1
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