[PATCH v2 1/2] counter: Add support for Quadrature x4 with swapped inputs

[PATCH v2 1/2] counter: Add support for Quadrature x4 with swapped inputs

[Jarkko Nikula]

Some Quadrature Encoders can swap phase inputs A and B internally. This
new function will allow drivers to configure input swap mode.

This was implemented by Felipe Balbi while he was working at Intel.

Signed-off-by: Felipe Balbi (Intel) <balbi@kernel.org>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
---
 Documentation/ABI/testing/sysfs-bus-counter | 4 ++++
 drivers/counter/counter.c                   | 3 ++-
 include/linux/counter.h                     | 3 ++-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
index 566bd99fe0a5..8f1e3de88c77 100644
--- a/Documentation/ABI/testing/sysfs-bus-counter
+++ b/Documentation/ABI/testing/sysfs-bus-counter
@@ -146,6 +146,10 @@ Description:
 			updates	the respective count. Quadrature encoding
 			determines the direction.
 
+		quadrature x4 swapped:
+			Same as quadrature x4, however Phase A and Phase B
+			signals are swapped.
+
 What:		/sys/bus/counter/devices/counterX/countY/name
 KernelVersion:	5.2
 Contact:	linux-iio@vger.kernel.org
diff --git a/drivers/counter/counter.c b/drivers/counter/counter.c
index 6a683d086008..11d357245b14 100644
--- a/drivers/counter/counter.c
+++ b/drivers/counter/counter.c
@@ -752,7 +752,8 @@ static const char *const counter_count_function_str[] = {
 	[COUNTER_COUNT_FUNCTION_QUADRATURE_X1_B] = "quadrature x1 b",
 	[COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A] = "quadrature x2 a",
 	[COUNTER_COUNT_FUNCTION_QUADRATURE_X2_B] = "quadrature x2 b",
-	[COUNTER_COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4"
+	[COUNTER_COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4",
+	[COUNTER_COUNT_FUNCTION_QUADRATURE_X4_SWAPPED] = "quadrature x4 swapped"
 };
 
 static ssize_t counter_function_show(struct device *dev,
diff --git a/include/linux/counter.h b/include/linux/counter.h
index 9dbd5df4cd34..c3b4d263eb22 100644
--- a/include/linux/counter.h
+++ b/include/linux/counter.h
@@ -170,7 +170,8 @@ enum counter_count_function {
 	COUNTER_COUNT_FUNCTION_QUADRATURE_X1_B,
 	COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A,
 	COUNTER_COUNT_FUNCTION_QUADRATURE_X2_B,
-	COUNTER_COUNT_FUNCTION_QUADRATURE_X4
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X4_SWAPPED,
 };
 
 /**
-- 
2.30.2

[PATCH v2 2/2] counter: Add support for Intel Quadrature Encoder Peripheral

[Jarkko Nikula]

Add support for Intel Quadrature Encoder Peripheral found on Intel
Elkhart Lake platform.

Initial implementation was done by Felipe Balbi while he was working at
Intel with later changes from Raymond Tan and me.

Co-developed-by: Felipe Balbi (Intel) <balbi@kernel.org>
Signed-off-by: Felipe Balbi (Intel) <balbi@kernel.org>
Co-developed-by: Raymond Tan <raymond.tan@intel.com>
Signed-off-by: Raymond Tan <raymond.tan@intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
---
v2:
- counter_to_qep() macro -> counter->priv
- Use sysfs_emit for user space returned values
- Use kstrbool for boolean values from userspace
- enable_write() reworked to be more readable
- Reworked synapse action control and new sysfs attribute "invert"
  * Action control before was wrong - what HW does is signal inversion.
    Implemented "invert" sysfs attribute for it and read-only action
    mode sysfs returning constant "both edges"
- Renamed sysfs attribe "noise" as "spike_filter_ns" and define
  programmable spike filter in terms of nanoseconds instead of raw
  register value
- Above and "ceiling" sysfs attribe changed as count extensions instead
  of device extensions
- Signal IDs rearranged to be zero based in order to prepare for counter
  character device interface patches in order to ensure same userspace
  sysfs paths
- Initializer macros for counter_signal and counter_synapse
  initialization
- Grouping intel_qep_counter_ops, intel_qep_signal_ext and enums near to
  their callback functions and use
- "invert" and "spike_filter_ns" sysfs attributes documented
- Other minor changes like local variable and empty line removal, etc

v1: https://www.spinics.net/lists/linux-iio/msg59652.html
---
 Documentation/ABI/testing/sysfs-bus-counter |  19 +
 drivers/counter/Kconfig                     |  10 +
 drivers/counter/Makefile                    |   1 +
 drivers/counter/intel-qep.c                 | 651 ++++++++++++++++++++
 4 files changed, 681 insertions(+)
 create mode 100644 drivers/counter/intel-qep.c

diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
index 8f1e3de88c77..19bdb32d450a 100644
--- a/Documentation/ABI/testing/sysfs-bus-counter
+++ b/Documentation/ABI/testing/sysfs-bus-counter
@@ -197,6 +197,15 @@ Description:
 		both edges:
 			Any state transition.
 
+What:		/sys/bus/counter/devices/counterX/countY/spike_filter_ns
+KernelVersion:	5.14
+Contact:	linux-iio@vger.kernel.org
+Description:
+		If the counter device supports programmable spike filter this
+		attribute indicates the value in nanoseconds where noise pulses
+		shorter or equal to configured value are ignored. Value 0 means
+		filter is disabled.
+
 What:		/sys/bus/counter/devices/counterX/name
 KernelVersion:	5.2
 Contact:	linux-iio@vger.kernel.org
@@ -232,3 +241,13 @@ Description:
 		Read-only attribute that indicates the device-specific name of
 		Signal Y. If possible, this should match the name of the
 		respective signal as it appears in the device datasheet.
+
+What:		/sys/bus/counter/devices/counterX/signalY/invert
+KernelVersion:	5.14
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Whether signal Y inversion is enabled. Valid attribute values
+		are boolean.
+
+		For counter devices that have feature to control inversion of
+		signal Y.
diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
index 5328705aa09c..d5d2540b30c2 100644
--- a/drivers/counter/Kconfig
+++ b/drivers/counter/Kconfig
@@ -91,4 +91,14 @@ config MICROCHIP_TCB_CAPTURE
 	  To compile this driver as a module, choose M here: the
 	  module will be called microchip-tcb-capture.
 
+config INTEL_QEP
+	tristate "Intel Quadrature Encoder Peripheral driver"
+	depends on PCI
+	help
+	  Select this option to enable the Intel Quadrature Encoder Peripheral
+	  driver.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called intel-qep.
+
 endif # COUNTER
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index cb646ed2f039..19742e6f5e3e 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -12,3 +12,4 @@ obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
 obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
 obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
 obj-$(CONFIG_MICROCHIP_TCB_CAPTURE)	+= microchip-tcb-capture.o
+obj-$(CONFIG_INTEL_QEP)		+= intel-qep.o
diff --git a/drivers/counter/intel-qep.c b/drivers/counter/intel-qep.c
new file mode 100644
index 000000000000..d3a5e4e93794
--- /dev/null
+++ b/drivers/counter/intel-qep.c
@@ -0,0 +1,651 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel Quadrature Encoder Peripheral driver
+ *
+ * Copyright (C) 2019-2021 Intel Corporation
+ *
+ * Author: Felipe Balbi (Intel)
+ * Author: Jarkko Nikula <jarkko.nikula@linux.intel.com>
+ * Author: Raymond Tan <raymond.tan@intel.com>
+ */
+#include <linux/bitops.h>
+#include <linux/counter.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/pm_runtime.h>
+
+#define INTEL_QEPCON			0x00
+#define INTEL_QEPFLT			0x04
+#define INTEL_QEPCOUNT			0x08
+#define INTEL_QEPMAX			0x0c
+#define INTEL_QEPWDT			0x10
+#define INTEL_QEPCAPDIV			0x14
+#define INTEL_QEPCNTR			0x18
+#define INTEL_QEPCAPBUF			0x1c
+#define INTEL_QEPINT_STAT		0x20
+#define INTEL_QEPINT_MASK		0x24
+
+/* QEPCON */
+#define INTEL_QEPCON_EN			BIT(0)
+#define INTEL_QEPCON_FLT_EN		BIT(1)
+#define INTEL_QEPCON_EDGE_A		BIT(2)
+#define INTEL_QEPCON_EDGE_B		BIT(3)
+#define INTEL_QEPCON_EDGE_INDX		BIT(4)
+#define INTEL_QEPCON_SWPAB		BIT(5)
+#define INTEL_QEPCON_OP_MODE		BIT(6)
+#define INTEL_QEPCON_PH_ERR		BIT(7)
+#define INTEL_QEPCON_COUNT_RST_MODE	BIT(8)
+#define INTEL_QEPCON_INDX_GATING_MASK	GENMASK(10, 9)
+#define INTEL_QEPCON_INDX_GATING(n)	(((n) & 3) << 9)
+#define INTEL_QEPCON_INDX_PAL_PBL	INTEL_QEPCON_INDX_GATING(0)
+#define INTEL_QEPCON_INDX_PAL_PBH	INTEL_QEPCON_INDX_GATING(1)
+#define INTEL_QEPCON_INDX_PAH_PBL	INTEL_QEPCON_INDX_GATING(2)
+#define INTEL_QEPCON_INDX_PAH_PBH	INTEL_QEPCON_INDX_GATING(3)
+#define INTEL_QEPCON_CAP_MODE		BIT(11)
+#define INTEL_QEPCON_FIFO_THRE_MASK	GENMASK(14, 12)
+#define INTEL_QEPCON_FIFO_THRE(n)	((((n) - 1) & 7) << 12)
+#define INTEL_QEPCON_FIFO_EMPTY		BIT(15)
+
+/* QEPFLT */
+#define INTEL_QEPFLT_MAX_COUNT(n)	((n) & 0x1fffff)
+
+/* QEPINT */
+#define INTEL_QEPINT_FIFOCRIT		BIT(5)
+#define INTEL_QEPINT_FIFOENTRY		BIT(4)
+#define INTEL_QEPINT_QEPDIR		BIT(3)
+#define INTEL_QEPINT_QEPRST_UP		BIT(2)
+#define INTEL_QEPINT_QEPRST_DOWN	BIT(1)
+#define INTEL_QEPINT_WDT		BIT(0)
+
+#define INTEL_QEPINT_MASK_ALL		GENMASK(5, 0)
+
+#define INTEL_QEP_CLK_PERIOD_NS		10
+
+#define INTEL_QEP_COUNTER_EXT_RW(_name) \
+{ \
+	.name = #_name, \
+	.read = _name##_read, \
+	.write = _name##_write, \
+}
+
+struct intel_qep {
+	struct counter_device counter;
+	struct mutex lock;
+	struct device *dev;
+	void __iomem *regs;
+	bool enabled;
+	/* Context save registers */
+	u32 qepcon;
+	u32 qepflt;
+	u32 qepmax;
+};
+
+static inline u32 intel_qep_readl(struct intel_qep *qep, u32 offset)
+{
+	return readl(qep->regs + offset);
+}
+
+static inline void intel_qep_writel(struct intel_qep *qep,
+				    u32 offset, u32 value)
+{
+	writel(value, qep->regs + offset);
+}
+
+static void intel_qep_init(struct intel_qep *qep)
+{
+	u32 reg;
+
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	reg &= ~INTEL_QEPCON_EN;
+	intel_qep_writel(qep, INTEL_QEPCON, reg);
+	qep->enabled = false;
+	/*
+	 * Make sure peripheral is disabled by flushing the write with
+	 * a dummy read
+	 */
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+
+	reg &= ~(INTEL_QEPCON_OP_MODE | INTEL_QEPCON_FLT_EN);
+	reg |= INTEL_QEPCON_EDGE_A | INTEL_QEPCON_EDGE_B |
+	       INTEL_QEPCON_EDGE_INDX | INTEL_QEPCON_COUNT_RST_MODE;
+	intel_qep_writel(qep, INTEL_QEPCON, reg);
+	intel_qep_writel(qep, INTEL_QEPINT_MASK, INTEL_QEPINT_MASK_ALL);
+}
+
+static int intel_qep_count_read(struct counter_device *counter,
+				struct counter_count *count,
+				unsigned long *val)
+{
+	struct intel_qep *const qep = counter->priv;
+
+	pm_runtime_get_sync(qep->dev);
+	*val = intel_qep_readl(qep, INTEL_QEPCOUNT);
+	pm_runtime_put(qep->dev);
+
+	return 0;
+}
+
+enum intel_qep_count_function {
+	INTEL_QEP_ENCODER_MODE_NORMAL,
+	INTEL_QEP_ENCODER_MODE_SWAPPED,
+};
+
+static const enum counter_count_function intel_qep_count_functions[] = {
+	[INTEL_QEP_ENCODER_MODE_NORMAL] =
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
+
+	[INTEL_QEP_ENCODER_MODE_SWAPPED] =
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X4_SWAPPED,
+};
+
+static int intel_qep_function_get(struct counter_device *counter,
+				  struct counter_count *count,
+				  size_t *function)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg;
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	pm_runtime_put(qep->dev);
+	if (reg & INTEL_QEPCON_SWPAB)
+		*function = INTEL_QEP_ENCODER_MODE_SWAPPED;
+	else
+		*function = INTEL_QEP_ENCODER_MODE_NORMAL;
+
+	return 0;
+}
+
+static int intel_qep_function_set(struct counter_device *counter,
+				  struct counter_count *count,
+				  size_t function)
+{
+	struct intel_qep *qep = counter->priv;
+	int ret = 0;
+	u32 reg;
+
+	mutex_lock(&qep->lock);
+	if (qep->enabled) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	if (function == INTEL_QEP_ENCODER_MODE_SWAPPED)
+		reg |= INTEL_QEPCON_SWPAB;
+	else
+		reg &= ~INTEL_QEPCON_SWPAB;
+	intel_qep_writel(qep, INTEL_QEPCON, reg);
+	pm_runtime_put(qep->dev);
+
+out:
+	mutex_unlock(&qep->lock);
+	return ret;
+}
+
+static const enum counter_synapse_action intel_qep_synapse_actions[] = {
+	COUNTER_SYNAPSE_ACTION_BOTH_EDGES,
+};
+
+static int intel_qep_action_get(struct counter_device *counter,
+				struct counter_count *count,
+				struct counter_synapse *synapse,
+				size_t *action)
+{
+	*action = 0;
+	return 0;
+}
+
+static const struct counter_ops intel_qep_counter_ops = {
+	.count_read = intel_qep_count_read,
+	.function_get = intel_qep_function_get,
+	.function_set = intel_qep_function_set,
+	.action_get = intel_qep_action_get,
+};
+
+static ssize_t intel_qep_signal_invert_read(struct counter_device *counter,
+					    struct counter_signal *signal,
+					    void *priv, char *buf)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg;
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	pm_runtime_put(qep->dev);
+
+	return sysfs_emit(buf, "%u\n", !(reg & (uintptr_t)signal->priv));
+}
+
+static ssize_t intel_qep_signal_invert_write(struct counter_device *counter,
+					     struct counter_signal *signal,
+					     void *priv, const char *buf,
+					     size_t len)
+{
+	struct intel_qep *qep = counter->priv;
+	bool invert;
+	int ret;
+	u32 reg;
+
+	ret = kstrtobool(buf, &invert);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&qep->lock);
+	if (qep->enabled) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	if (invert == true)
+		reg &= ~(uintptr_t)signal->priv;
+	else
+		reg |= (uintptr_t)signal->priv;
+	intel_qep_writel(qep, INTEL_QEPCON, reg);
+	pm_runtime_put(qep->dev);
+	ret = len;
+
+out:
+	mutex_unlock(&qep->lock);
+	return ret;
+}
+
+static const struct counter_signal_ext intel_qep_signal_ext[] = {
+	{
+		.name = "invert",
+		.read = intel_qep_signal_invert_read,
+		.write = intel_qep_signal_invert_write,
+	},
+};
+
+#define INTEL_QEP_SIGNAL(_id, _name, _priv) {		\
+	.id = (_id),					\
+	.name = (_name),				\
+	.ext = intel_qep_signal_ext,			\
+	.num_ext = ARRAY_SIZE(intel_qep_signal_ext),	\
+	.priv = (void *)_priv,				\
+}
+
+static struct counter_signal intel_qep_signals[] = {
+	INTEL_QEP_SIGNAL(0, "Phase A", INTEL_QEPCON_EDGE_A),
+	INTEL_QEP_SIGNAL(1, "Phase B", INTEL_QEPCON_EDGE_A),
+	INTEL_QEP_SIGNAL(2, "Index", INTEL_QEPCON_EDGE_A),
+};
+
+#define INTEL_QEP_SYNAPSE(_signal_id) {				\
+	.actions_list = intel_qep_synapse_actions,		\
+	.num_actions = ARRAY_SIZE(intel_qep_synapse_actions),	\
+	.signal = &intel_qep_signals[(_signal_id)],		\
+}
+
+static struct counter_synapse intel_qep_count_synapses[] = {
+	INTEL_QEP_SYNAPSE(0),
+	INTEL_QEP_SYNAPSE(1),
+	INTEL_QEP_SYNAPSE(2),
+};
+
+static ssize_t ceiling_read(struct counter_device *counter,
+			    struct counter_count *count,
+			    void *priv, char *buf)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg;
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPMAX);
+	pm_runtime_put(qep->dev);
+
+	return sysfs_emit(buf, "%u\n", reg);
+}
+
+static ssize_t ceiling_write(struct counter_device *counter,
+			     struct counter_count *count,
+			     void *priv, const char *buf, size_t len)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 max;
+	int ret;
+
+	ret = kstrtou32(buf, 0, &max);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&qep->lock);
+	if (qep->enabled) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	pm_runtime_get_sync(qep->dev);
+	intel_qep_writel(qep, INTEL_QEPMAX, max);
+	pm_runtime_put(qep->dev);
+	ret = len;
+
+out:
+	mutex_unlock(&qep->lock);
+	return ret;
+}
+
+static ssize_t enable_read(struct counter_device *counter,
+			   struct counter_count *count,
+			   void *priv, char *buf)
+{
+	struct intel_qep *qep = counter->priv;
+
+	return sysfs_emit(buf, "%u\n", qep->enabled);
+}
+
+static ssize_t enable_write(struct counter_device *counter,
+			    struct counter_count *count,
+			    void *priv, const char *buf, size_t len)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg;
+	bool val, changed;
+	int ret;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	mutex_lock(&qep->lock);
+	changed = val ^ qep->enabled;
+	if (!changed)
+		goto out;
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	if (val) {
+		/* Enable peripheral and keep runtime PM always on */
+		reg |= INTEL_QEPCON_EN;
+		pm_runtime_get_noresume(qep->dev);
+	} else {
+		/* Let runtime PM be idle and disable peripheral */
+		pm_runtime_put_noidle(qep->dev);
+		reg &= ~INTEL_QEPCON_EN;
+	}
+	intel_qep_writel(qep, INTEL_QEPCON, reg);
+	pm_runtime_put(qep->dev);
+	qep->enabled = val;
+
+out:
+	mutex_unlock(&qep->lock);
+	return len;
+}
+
+static ssize_t spike_filter_ns_read(struct counter_device *counter,
+				    struct counter_count *count,
+				    void *priv, char *buf)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg;
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	if (!(reg & INTEL_QEPCON_FLT_EN)) {
+		pm_runtime_put(qep->dev);
+		return sysfs_emit(buf, "0\n");
+	}
+	reg = INTEL_QEPFLT_MAX_COUNT(intel_qep_readl(qep, INTEL_QEPFLT));
+	pm_runtime_put(qep->dev);
+
+	return sysfs_emit(buf, "%u\n", (reg + 2) * INTEL_QEP_CLK_PERIOD_NS);
+}
+
+static ssize_t spike_filter_ns_write(struct counter_device *counter,
+				     struct counter_count *count,
+				     void *priv, const char *buf, size_t len)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg, length;
+	bool enable;
+	int ret;
+
+	ret = kstrtou32(buf, 0, &length);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Spike filter length is (MAX_COUNT + 2) clock periods. Disable
+	 * filter when user space supplies shorter than 2 clock periods and
+	 * otherwise enable and set MAX_COUNT = clock periods - 2.
+	 */
+	length /= INTEL_QEP_CLK_PERIOD_NS;
+	if (length < 2) {
+		enable = false;
+		length = 0;
+	} else {
+		enable = true;
+		length -= 2;
+	}
+
+	if (length > INTEL_QEPFLT_MAX_COUNT(length))
+		return -EINVAL;
+
+	mutex_lock(&qep->lock);
+	if (qep->enabled) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	if (enable)
+		reg |= INTEL_QEPCON_FLT_EN;
+	else
+		reg &= ~INTEL_QEPCON_FLT_EN;
+	intel_qep_writel(qep, INTEL_QEPFLT, length);
+	intel_qep_writel(qep, INTEL_QEPCON, reg);
+	pm_runtime_put(qep->dev);
+	ret = len;
+
+out:
+	mutex_unlock(&qep->lock);
+	return ret;
+}
+
+static ssize_t preset_enable_read(struct counter_device *counter,
+				  struct counter_count *count,
+				  void *priv, char *buf)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg;
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	pm_runtime_put(qep->dev);
+	return sysfs_emit(buf, "%u\n", !(reg & INTEL_QEPCON_COUNT_RST_MODE));
+}
+
+static ssize_t preset_enable_write(struct counter_device *counter,
+				   struct counter_count *count,
+				   void *priv, const char *buf, size_t len)
+{
+	struct intel_qep *qep = counter->priv;
+	u32 reg;
+	bool val;
+	int ret;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	mutex_lock(&qep->lock);
+	if (qep->enabled) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	pm_runtime_get_sync(qep->dev);
+	reg = intel_qep_readl(qep, INTEL_QEPCON);
+	if (val)
+		reg &= ~INTEL_QEPCON_COUNT_RST_MODE;
+	else
+		reg |= INTEL_QEPCON_COUNT_RST_MODE;
+
+	intel_qep_writel(qep, INTEL_QEPCON, reg);
+	pm_runtime_put(qep->dev);
+	ret = len;
+
+out:
+	mutex_unlock(&qep->lock);
+
+	return ret;
+}
+
+static const struct counter_count_ext intel_qep_count_ext[] = {
+	INTEL_QEP_COUNTER_EXT_RW(ceiling),
+	INTEL_QEP_COUNTER_EXT_RW(enable),
+	INTEL_QEP_COUNTER_EXT_RW(spike_filter_ns),
+	INTEL_QEP_COUNTER_EXT_RW(preset_enable)
+};
+
+static struct counter_count intel_qep_counter_count[] = {
+	{
+		.id = 0,
+		.name = "Channel 1 Count",
+		.functions_list = intel_qep_count_functions,
+		.num_functions = ARRAY_SIZE(intel_qep_count_functions),
+		.synapses = intel_qep_count_synapses,
+		.num_synapses = ARRAY_SIZE(intel_qep_count_synapses),
+		.ext = intel_qep_count_ext,
+		.num_ext = ARRAY_SIZE(intel_qep_count_ext),
+	},
+};
+
+static int intel_qep_probe(struct pci_dev *pci, const struct pci_device_id *id)
+{
+	struct intel_qep *qep;
+	struct device *dev = &pci->dev;
+	void __iomem *regs;
+	int ret;
+
+	qep = devm_kzalloc(dev, sizeof(*qep), GFP_KERNEL);
+	if (!qep)
+		return -ENOMEM;
+
+	ret = pcim_enable_device(pci);
+	if (ret)
+		return ret;
+
+	pci_set_master(pci);
+
+	ret = pcim_iomap_regions(pci, BIT(0), pci_name(pci));
+	if (ret)
+		return ret;
+
+	regs = pcim_iomap_table(pci)[0];
+	if (!regs)
+		return -ENOMEM;
+
+	qep->dev = dev;
+	qep->regs = regs;
+	mutex_init(&qep->lock);
+
+	intel_qep_init(qep);
+	pci_set_drvdata(pci, qep);
+
+	qep->counter.name = pci_name(pci);
+	qep->counter.parent = dev;
+	qep->counter.ops = &intel_qep_counter_ops;
+	qep->counter.counts = intel_qep_counter_count;
+	qep->counter.num_counts = ARRAY_SIZE(intel_qep_counter_count);
+	qep->counter.signals = intel_qep_signals;
+	qep->counter.num_signals = ARRAY_SIZE(intel_qep_signals);
+	qep->counter.priv = qep;
+	qep->enabled = false;
+
+	pm_runtime_put(dev);
+	pm_runtime_allow(dev);
+
+	return devm_counter_register(&pci->dev, &qep->counter);
+}
+
+static void intel_qep_remove(struct pci_dev *pci)
+{
+	struct intel_qep *qep = pci_get_drvdata(pci);
+	struct device *dev = &pci->dev;
+
+	pm_runtime_forbid(dev);
+	if (!qep->enabled)
+		pm_runtime_get(dev);
+
+	intel_qep_writel(qep, INTEL_QEPCON, 0);
+}
+
+#ifdef CONFIG_PM
+static int intel_qep_suspend(struct device *dev)
+{
+	struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
+	struct intel_qep *qep = pci_get_drvdata(pdev);
+
+	qep->qepcon = intel_qep_readl(qep, INTEL_QEPCON);
+	qep->qepflt = intel_qep_readl(qep, INTEL_QEPFLT);
+	qep->qepmax = intel_qep_readl(qep, INTEL_QEPMAX);
+
+	return 0;
+}
+
+static int intel_qep_resume(struct device *dev)
+{
+	struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
+	struct intel_qep *qep = pci_get_drvdata(pdev);
+
+	/*
+	 * Make sure peripheral is disabled when restoring registers and
+	 * control register bits that are writable only when the peripheral
+	 * is disabled
+	 */
+	intel_qep_writel(qep, INTEL_QEPCON, 0);
+	intel_qep_readl(qep, INTEL_QEPCON);
+
+	intel_qep_writel(qep, INTEL_QEPFLT, qep->qepflt);
+	intel_qep_writel(qep, INTEL_QEPMAX, qep->qepmax);
+	intel_qep_writel(qep, INTEL_QEPINT_MASK, INTEL_QEPINT_MASK_ALL);
+
+	/* Restore all other control register bits except enable status */
+	intel_qep_writel(qep, INTEL_QEPCON, qep->qepcon & ~INTEL_QEPCON_EN);
+	intel_qep_readl(qep, INTEL_QEPCON);
+
+	/* Restore enable status */
+	intel_qep_writel(qep, INTEL_QEPCON, qep->qepcon);
+
+	return 0;
+}
+#endif
+
+static UNIVERSAL_DEV_PM_OPS(intel_qep_pm_ops,
+			    intel_qep_suspend, intel_qep_resume, NULL);
+
+static const struct pci_device_id intel_qep_id_table[] = {
+	/* EHL */
+	{ PCI_VDEVICE(INTEL, 0x4bc3), },
+	{ PCI_VDEVICE(INTEL, 0x4b81), },
+	{ PCI_VDEVICE(INTEL, 0x4b82), },
+	{ PCI_VDEVICE(INTEL, 0x4b83), },
+	{  } /* Terminating Entry */
+};
+MODULE_DEVICE_TABLE(pci, intel_qep_id_table);
+
+static struct pci_driver intel_qep_driver = {
+	.name = "intel-qep",
+	.id_table = intel_qep_id_table,
+	.probe = intel_qep_probe,
+	.remove = intel_qep_remove,
+	.driver = {
+		.pm = &intel_qep_pm_ops,
+	}
+};
+
+module_pci_driver(intel_qep_driver);
+
+MODULE_AUTHOR("Felipe Balbi (Intel)");
+MODULE_AUTHOR("Jarkko Nikula <jarkko.nikula@linux.intel.com>");
+MODULE_AUTHOR("Raymond Tan <raymond.tan@intel.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Intel Quadrature Encoder Peripheral driver");
-- 
2.30.2

Re: [PATCH v2 1/2] counter: Add support for Quadrature x4 with swapped inputs

[William Breathitt Gray]

[-- Attachment #1: Type: text/plain, Size: 2674 bytes --]

On Wed, May 26, 2021 at 06:06:00PM +0300, Jarkko Nikula wrote:
> Some Quadrature Encoders can swap phase inputs A and B internally. This
> new function will allow drivers to configure input swap mode.
> 
> This was implemented by Felipe Balbi while he was working at Intel.
> 
> Signed-off-by: Felipe Balbi (Intel) <balbi@kernel.org>
> Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>

There's no change in this patch from the last revision, right?

Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>

> ---
>  Documentation/ABI/testing/sysfs-bus-counter | 4 ++++
>  drivers/counter/counter.c                   | 3 ++-
>  include/linux/counter.h                     | 3 ++-
>  3 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
> index 566bd99fe0a5..8f1e3de88c77 100644
> --- a/Documentation/ABI/testing/sysfs-bus-counter
> +++ b/Documentation/ABI/testing/sysfs-bus-counter
> @@ -146,6 +146,10 @@ Description:
>  			updates	the respective count. Quadrature encoding
>  			determines the direction.
>  
> +		quadrature x4 swapped:
> +			Same as quadrature x4, however Phase A and Phase B
> +			signals are swapped.
> +
>  What:		/sys/bus/counter/devices/counterX/countY/name
>  KernelVersion:	5.2
>  Contact:	linux-iio@vger.kernel.org
> diff --git a/drivers/counter/counter.c b/drivers/counter/counter.c
> index 6a683d086008..11d357245b14 100644
> --- a/drivers/counter/counter.c
> +++ b/drivers/counter/counter.c
> @@ -752,7 +752,8 @@ static const char *const counter_count_function_str[] = {
>  	[COUNTER_COUNT_FUNCTION_QUADRATURE_X1_B] = "quadrature x1 b",
>  	[COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A] = "quadrature x2 a",
>  	[COUNTER_COUNT_FUNCTION_QUADRATURE_X2_B] = "quadrature x2 b",
> -	[COUNTER_COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4"
> +	[COUNTER_COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4",
> +	[COUNTER_COUNT_FUNCTION_QUADRATURE_X4_SWAPPED] = "quadrature x4 swapped"
>  };
>  
>  static ssize_t counter_function_show(struct device *dev,
> diff --git a/include/linux/counter.h b/include/linux/counter.h
> index 9dbd5df4cd34..c3b4d263eb22 100644
> --- a/include/linux/counter.h
> +++ b/include/linux/counter.h
> @@ -170,7 +170,8 @@ enum counter_count_function {
>  	COUNTER_COUNT_FUNCTION_QUADRATURE_X1_B,
>  	COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A,
>  	COUNTER_COUNT_FUNCTION_QUADRATURE_X2_B,
> -	COUNTER_COUNT_FUNCTION_QUADRATURE_X4
> +	COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
> +	COUNTER_COUNT_FUNCTION_QUADRATURE_X4_SWAPPED,
>  };
>  
>  /**
> -- 
> 2.30.2
> 

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH v2 2/2] counter: Add support for Intel Quadrature Encoder Peripheral

[William Breathitt Gray]

[-- Attachment #1: Type: text/plain, Size: 25040 bytes --]

On Wed, May 26, 2021 at 06:06:01PM +0300, Jarkko Nikula wrote:
> Add support for Intel Quadrature Encoder Peripheral found on Intel
> Elkhart Lake platform.
> 
> Initial implementation was done by Felipe Balbi while he was working at
> Intel with later changes from Raymond Tan and me.
> 
> Co-developed-by: Felipe Balbi (Intel) <balbi@kernel.org>
> Signed-off-by: Felipe Balbi (Intel) <balbi@kernel.org>
> Co-developed-by: Raymond Tan <raymond.tan@intel.com>
> Signed-off-by: Raymond Tan <raymond.tan@intel.com>
> Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>

Hello Jarkko,

Thank you for the update. I have some minor comments inline below.

> ---
> v2:
> - counter_to_qep() macro -> counter->priv
> - Use sysfs_emit for user space returned values
> - Use kstrbool for boolean values from userspace
> - enable_write() reworked to be more readable
> - Reworked synapse action control and new sysfs attribute "invert"
>   * Action control before was wrong - what HW does is signal inversion.
>     Implemented "invert" sysfs attribute for it and read-only action
>     mode sysfs returning constant "both edges"
> - Renamed sysfs attribe "noise" as "spike_filter_ns" and define
>   programmable spike filter in terms of nanoseconds instead of raw
>   register value
> - Above and "ceiling" sysfs attribe changed as count extensions instead
>   of device extensions
> - Signal IDs rearranged to be zero based in order to prepare for counter
>   character device interface patches in order to ensure same userspace
>   sysfs paths
> - Initializer macros for counter_signal and counter_synapse
>   initialization
> - Grouping intel_qep_counter_ops, intel_qep_signal_ext and enums near to
>   their callback functions and use
> - "invert" and "spike_filter_ns" sysfs attributes documented
> - Other minor changes like local variable and empty line removal, etc
> 
> v1: https://www.spinics.net/lists/linux-iio/msg59652.html
> ---
>  Documentation/ABI/testing/sysfs-bus-counter |  19 +
>  drivers/counter/Kconfig                     |  10 +
>  drivers/counter/Makefile                    |   1 +
>  drivers/counter/intel-qep.c                 | 651 ++++++++++++++++++++
>  4 files changed, 681 insertions(+)
>  create mode 100644 drivers/counter/intel-qep.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
> index 8f1e3de88c77..19bdb32d450a 100644
> --- a/Documentation/ABI/testing/sysfs-bus-counter
> +++ b/Documentation/ABI/testing/sysfs-bus-counter
> @@ -197,6 +197,15 @@ Description:
>  		both edges:
>  			Any state transition.
>  
> +What:		/sys/bus/counter/devices/counterX/countY/spike_filter_ns
> +KernelVersion:	5.14
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		If the counter device supports programmable spike filter this
> +		attribute indicates the value in nanoseconds where noise pulses
> +		shorter or equal to configured value are ignored. Value 0 means
> +		filter is disabled.
> +
>  What:		/sys/bus/counter/devices/counterX/name
>  KernelVersion:	5.2
>  Contact:	linux-iio@vger.kernel.org
> @@ -232,3 +241,13 @@ Description:
>  		Read-only attribute that indicates the device-specific name of
>  		Signal Y. If possible, this should match the name of the
>  		respective signal as it appears in the device datasheet.
> +
> +What:		/sys/bus/counter/devices/counterX/signalY/invert
> +KernelVersion:	5.14
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Whether signal Y inversion is enabled. Valid attribute values
> +		are boolean.
> +
> +		For counter devices that have feature to control inversion of
> +		signal Y.

I want to understand this functionality a bit better. So, this device
has two quadrature encoder signals coming in (Phase A and Phase B) and
this "invert" option allows the user to configure the device to invert
these signals in hardware before before they are evaluated by the
quadrature encoding counter. Users are able to invert each signal
independent of the other; e.g. Phase A can be inverted, but Phase B can
be left alone. Is my understanding correct, or is the inversion applied
across all signals rather than just one independently?

What is the purpose of this functionality? Is this to allow users to
adjust the direction of the count without having to physically reorient
the encoding device (e.g. tracking counter-clockwise versus clockwise
movement)?

> diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
> index 5328705aa09c..d5d2540b30c2 100644
> --- a/drivers/counter/Kconfig
> +++ b/drivers/counter/Kconfig
> @@ -91,4 +91,14 @@ config MICROCHIP_TCB_CAPTURE
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called microchip-tcb-capture.
>  
> +config INTEL_QEP
> +	tristate "Intel Quadrature Encoder Peripheral driver"
> +	depends on PCI
> +	help
> +	  Select this option to enable the Intel Quadrature Encoder Peripheral
> +	  driver.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called intel-qep.
> +
>  endif # COUNTER
> diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
> index cb646ed2f039..19742e6f5e3e 100644
> --- a/drivers/counter/Makefile
> +++ b/drivers/counter/Makefile
> @@ -12,3 +12,4 @@ obj-$(CONFIG_STM32_LPTIMER_CNT)	+= stm32-lptimer-cnt.o
>  obj-$(CONFIG_TI_EQEP)		+= ti-eqep.o
>  obj-$(CONFIG_FTM_QUADDEC)	+= ftm-quaddec.o
>  obj-$(CONFIG_MICROCHIP_TCB_CAPTURE)	+= microchip-tcb-capture.o
> +obj-$(CONFIG_INTEL_QEP)		+= intel-qep.o
> diff --git a/drivers/counter/intel-qep.c b/drivers/counter/intel-qep.c
> new file mode 100644
> index 000000000000..d3a5e4e93794
> --- /dev/null
> +++ b/drivers/counter/intel-qep.c
> @@ -0,0 +1,651 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Intel Quadrature Encoder Peripheral driver
> + *
> + * Copyright (C) 2019-2021 Intel Corporation
> + *
> + * Author: Felipe Balbi (Intel)
> + * Author: Jarkko Nikula <jarkko.nikula@linux.intel.com>
> + * Author: Raymond Tan <raymond.tan@intel.com>
> + */
> +#include <linux/bitops.h>
> +#include <linux/counter.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pci.h>
> +#include <linux/pm_runtime.h>
> +
> +#define INTEL_QEPCON			0x00
> +#define INTEL_QEPFLT			0x04
> +#define INTEL_QEPCOUNT			0x08
> +#define INTEL_QEPMAX			0x0c
> +#define INTEL_QEPWDT			0x10
> +#define INTEL_QEPCAPDIV			0x14
> +#define INTEL_QEPCNTR			0x18
> +#define INTEL_QEPCAPBUF			0x1c
> +#define INTEL_QEPINT_STAT		0x20
> +#define INTEL_QEPINT_MASK		0x24
> +
> +/* QEPCON */
> +#define INTEL_QEPCON_EN			BIT(0)
> +#define INTEL_QEPCON_FLT_EN		BIT(1)
> +#define INTEL_QEPCON_EDGE_A		BIT(2)
> +#define INTEL_QEPCON_EDGE_B		BIT(3)
> +#define INTEL_QEPCON_EDGE_INDX		BIT(4)
> +#define INTEL_QEPCON_SWPAB		BIT(5)
> +#define INTEL_QEPCON_OP_MODE		BIT(6)
> +#define INTEL_QEPCON_PH_ERR		BIT(7)
> +#define INTEL_QEPCON_COUNT_RST_MODE	BIT(8)
> +#define INTEL_QEPCON_INDX_GATING_MASK	GENMASK(10, 9)
> +#define INTEL_QEPCON_INDX_GATING(n)	(((n) & 3) << 9)
> +#define INTEL_QEPCON_INDX_PAL_PBL	INTEL_QEPCON_INDX_GATING(0)
> +#define INTEL_QEPCON_INDX_PAL_PBH	INTEL_QEPCON_INDX_GATING(1)
> +#define INTEL_QEPCON_INDX_PAH_PBL	INTEL_QEPCON_INDX_GATING(2)
> +#define INTEL_QEPCON_INDX_PAH_PBH	INTEL_QEPCON_INDX_GATING(3)
> +#define INTEL_QEPCON_CAP_MODE		BIT(11)
> +#define INTEL_QEPCON_FIFO_THRE_MASK	GENMASK(14, 12)
> +#define INTEL_QEPCON_FIFO_THRE(n)	((((n) - 1) & 7) << 12)
> +#define INTEL_QEPCON_FIFO_EMPTY		BIT(15)
> +
> +/* QEPFLT */
> +#define INTEL_QEPFLT_MAX_COUNT(n)	((n) & 0x1fffff)
> +
> +/* QEPINT */
> +#define INTEL_QEPINT_FIFOCRIT		BIT(5)
> +#define INTEL_QEPINT_FIFOENTRY		BIT(4)
> +#define INTEL_QEPINT_QEPDIR		BIT(3)
> +#define INTEL_QEPINT_QEPRST_UP		BIT(2)
> +#define INTEL_QEPINT_QEPRST_DOWN	BIT(1)
> +#define INTEL_QEPINT_WDT		BIT(0)
> +
> +#define INTEL_QEPINT_MASK_ALL		GENMASK(5, 0)
> +
> +#define INTEL_QEP_CLK_PERIOD_NS		10
> +
> +#define INTEL_QEP_COUNTER_EXT_RW(_name) \
> +{ \
> +	.name = #_name, \
> +	.read = _name##_read, \
> +	.write = _name##_write, \
> +}
> +
> +struct intel_qep {
> +	struct counter_device counter;
> +	struct mutex lock;
> +	struct device *dev;
> +	void __iomem *regs;
> +	bool enabled;
> +	/* Context save registers */
> +	u32 qepcon;
> +	u32 qepflt;
> +	u32 qepmax;
> +};
> +
> +static inline u32 intel_qep_readl(struct intel_qep *qep, u32 offset)
> +{
> +	return readl(qep->regs + offset);
> +}
> +
> +static inline void intel_qep_writel(struct intel_qep *qep,
> +				    u32 offset, u32 value)
> +{
> +	writel(value, qep->regs + offset);
> +}
> +
> +static void intel_qep_init(struct intel_qep *qep)
> +{
> +	u32 reg;
> +
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	reg &= ~INTEL_QEPCON_EN;
> +	intel_qep_writel(qep, INTEL_QEPCON, reg);
> +	qep->enabled = false;
> +	/*
> +	 * Make sure peripheral is disabled by flushing the write with
> +	 * a dummy read
> +	 */
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +
> +	reg &= ~(INTEL_QEPCON_OP_MODE | INTEL_QEPCON_FLT_EN);
> +	reg |= INTEL_QEPCON_EDGE_A | INTEL_QEPCON_EDGE_B |
> +	       INTEL_QEPCON_EDGE_INDX | INTEL_QEPCON_COUNT_RST_MODE;
> +	intel_qep_writel(qep, INTEL_QEPCON, reg);
> +	intel_qep_writel(qep, INTEL_QEPINT_MASK, INTEL_QEPINT_MASK_ALL);
> +}
> +
> +static int intel_qep_count_read(struct counter_device *counter,
> +				struct counter_count *count,
> +				unsigned long *val)
> +{
> +	struct intel_qep *const qep = counter->priv;
> +
> +	pm_runtime_get_sync(qep->dev);
> +	*val = intel_qep_readl(qep, INTEL_QEPCOUNT);
> +	pm_runtime_put(qep->dev);
> +
> +	return 0;
> +}
> +
> +enum intel_qep_count_function {
> +	INTEL_QEP_ENCODER_MODE_NORMAL,
> +	INTEL_QEP_ENCODER_MODE_SWAPPED,
> +};
> +
> +static const enum counter_count_function intel_qep_count_functions[] = {
> +	[INTEL_QEP_ENCODER_MODE_NORMAL] =
> +	COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
> +
> +	[INTEL_QEP_ENCODER_MODE_SWAPPED] =
> +	COUNTER_COUNT_FUNCTION_QUADRATURE_X4_SWAPPED,
> +};
> +
> +static int intel_qep_function_get(struct counter_device *counter,
> +				  struct counter_count *count,
> +				  size_t *function)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg;
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	pm_runtime_put(qep->dev);
> +	if (reg & INTEL_QEPCON_SWPAB)
> +		*function = INTEL_QEP_ENCODER_MODE_SWAPPED;
> +	else
> +		*function = INTEL_QEP_ENCODER_MODE_NORMAL;
> +
> +	return 0;
> +}
> +
> +static int intel_qep_function_set(struct counter_device *counter,
> +				  struct counter_count *count,
> +				  size_t function)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	int ret = 0;
> +	u32 reg;
> +
> +	mutex_lock(&qep->lock);
> +	if (qep->enabled) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	if (function == INTEL_QEP_ENCODER_MODE_SWAPPED)
> +		reg |= INTEL_QEPCON_SWPAB;
> +	else
> +		reg &= ~INTEL_QEPCON_SWPAB;
> +	intel_qep_writel(qep, INTEL_QEPCON, reg);
> +	pm_runtime_put(qep->dev);
> +
> +out:
> +	mutex_unlock(&qep->lock);
> +	return ret;
> +}
> +
> +static const enum counter_synapse_action intel_qep_synapse_actions[] = {
> +	COUNTER_SYNAPSE_ACTION_BOTH_EDGES,
> +};
> +
> +static int intel_qep_action_get(struct counter_device *counter,
> +				struct counter_count *count,
> +				struct counter_synapse *synapse,
> +				size_t *action)
> +{
> +	*action = 0;
> +	return 0;
> +}
> +
> +static const struct counter_ops intel_qep_counter_ops = {
> +	.count_read = intel_qep_count_read,
> +	.function_get = intel_qep_function_get,
> +	.function_set = intel_qep_function_set,
> +	.action_get = intel_qep_action_get,
> +};
> +
> +static ssize_t intel_qep_signal_invert_read(struct counter_device *counter,
> +					    struct counter_signal *signal,
> +					    void *priv, char *buf)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg;
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	pm_runtime_put(qep->dev);
> +
> +	return sysfs_emit(buf, "%u\n", !(reg & (uintptr_t)signal->priv));

It's easy to forget what signal->priv represents. I recommend using a
variable to hold this value so that the logic is a bit easier to
understand for future reviewers.

> +}
> +
> +static ssize_t intel_qep_signal_invert_write(struct counter_device *counter,
> +					     struct counter_signal *signal,
> +					     void *priv, const char *buf,
> +					     size_t len)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	bool invert;
> +	int ret;
> +	u32 reg;
> +
> +	ret = kstrtobool(buf, &invert);
> +	if (ret < 0)
> +		return ret;
> +
> +	mutex_lock(&qep->lock);
> +	if (qep->enabled) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	if (invert == true)
> +		reg &= ~(uintptr_t)signal->priv;
> +	else
> +		reg |= (uintptr_t)signal->priv;

Same comment as above about signal->priv: using a named variable should
make this easier to understand.

> +	intel_qep_writel(qep, INTEL_QEPCON, reg);
> +	pm_runtime_put(qep->dev);
> +	ret = len;
> +
> +out:
> +	mutex_unlock(&qep->lock);
> +	return ret;
> +}
> +
> +static const struct counter_signal_ext intel_qep_signal_ext[] = {
> +	{
> +		.name = "invert",
> +		.read = intel_qep_signal_invert_read,
> +		.write = intel_qep_signal_invert_write,
> +	},
> +};
> +
> +#define INTEL_QEP_SIGNAL(_id, _name, _priv) {		\
> +	.id = (_id),					\
> +	.name = (_name),				\
> +	.ext = intel_qep_signal_ext,			\
> +	.num_ext = ARRAY_SIZE(intel_qep_signal_ext),	\
> +	.priv = (void *)_priv,				\
> +}
> +
> +static struct counter_signal intel_qep_signals[] = {
> +	INTEL_QEP_SIGNAL(0, "Phase A", INTEL_QEPCON_EDGE_A),
> +	INTEL_QEP_SIGNAL(1, "Phase B", INTEL_QEPCON_EDGE_A),
> +	INTEL_QEP_SIGNAL(2, "Index", INTEL_QEPCON_EDGE_A),

Is INTEL_QEPCON_EDGE_A three times here correct, or did mean to use
INTEL_QEPCON_EDGE_B and INTEL_QEPCON_EDGE_INDX as well?

> +};
> +
> +#define INTEL_QEP_SYNAPSE(_signal_id) {				\
> +	.actions_list = intel_qep_synapse_actions,		\
> +	.num_actions = ARRAY_SIZE(intel_qep_synapse_actions),	\
> +	.signal = &intel_qep_signals[(_signal_id)],		\
> +}
> +
> +static struct counter_synapse intel_qep_count_synapses[] = {
> +	INTEL_QEP_SYNAPSE(0),
> +	INTEL_QEP_SYNAPSE(1),
> +	INTEL_QEP_SYNAPSE(2),
> +};
> +
> +static ssize_t ceiling_read(struct counter_device *counter,
> +			    struct counter_count *count,
> +			    void *priv, char *buf)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg;
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPMAX);
> +	pm_runtime_put(qep->dev);
> +
> +	return sysfs_emit(buf, "%u\n", reg);
> +}
> +
> +static ssize_t ceiling_write(struct counter_device *counter,
> +			     struct counter_count *count,
> +			     void *priv, const char *buf, size_t len)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 max;
> +	int ret;
> +
> +	ret = kstrtou32(buf, 0, &max);
> +	if (ret < 0)
> +		return ret;
> +
> +	mutex_lock(&qep->lock);
> +	if (qep->enabled) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	pm_runtime_get_sync(qep->dev);
> +	intel_qep_writel(qep, INTEL_QEPMAX, max);
> +	pm_runtime_put(qep->dev);
> +	ret = len;
> +
> +out:
> +	mutex_unlock(&qep->lock);
> +	return ret;
> +}
> +
> +static ssize_t enable_read(struct counter_device *counter,
> +			   struct counter_count *count,
> +			   void *priv, char *buf)
> +{
> +	struct intel_qep *qep = counter->priv;
> +
> +	return sysfs_emit(buf, "%u\n", qep->enabled);
> +}
> +
> +static ssize_t enable_write(struct counter_device *counter,
> +			    struct counter_count *count,
> +			    void *priv, const char *buf, size_t len)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg;
> +	bool val, changed;
> +	int ret;
> +
> +	ret = kstrtobool(buf, &val);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&qep->lock);
> +	changed = val ^ qep->enabled;
> +	if (!changed)
> +		goto out;
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	if (val) {
> +		/* Enable peripheral and keep runtime PM always on */
> +		reg |= INTEL_QEPCON_EN;
> +		pm_runtime_get_noresume(qep->dev);
> +	} else {
> +		/* Let runtime PM be idle and disable peripheral */
> +		pm_runtime_put_noidle(qep->dev);
> +		reg &= ~INTEL_QEPCON_EN;
> +	}
> +	intel_qep_writel(qep, INTEL_QEPCON, reg);
> +	pm_runtime_put(qep->dev);
> +	qep->enabled = val;
> +
> +out:
> +	mutex_unlock(&qep->lock);
> +	return len;
> +}
> +
> +static ssize_t spike_filter_ns_read(struct counter_device *counter,
> +				    struct counter_count *count,
> +				    void *priv, char *buf)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg;
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	if (!(reg & INTEL_QEPCON_FLT_EN)) {
> +		pm_runtime_put(qep->dev);
> +		return sysfs_emit(buf, "0\n");
> +	}
> +	reg = INTEL_QEPFLT_MAX_COUNT(intel_qep_readl(qep, INTEL_QEPFLT));
> +	pm_runtime_put(qep->dev);
> +
> +	return sysfs_emit(buf, "%u\n", (reg + 2) * INTEL_QEP_CLK_PERIOD_NS);
> +}
> +
> +static ssize_t spike_filter_ns_write(struct counter_device *counter,
> +				     struct counter_count *count,
> +				     void *priv, const char *buf, size_t len)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg, length;
> +	bool enable;
> +	int ret;
> +
> +	ret = kstrtou32(buf, 0, &length);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * Spike filter length is (MAX_COUNT + 2) clock periods. Disable
> +	 * filter when user space supplies shorter than 2 clock periods and
> +	 * otherwise enable and set MAX_COUNT = clock periods - 2.
> +	 */
> +	length /= INTEL_QEP_CLK_PERIOD_NS;
> +	if (length < 2) {

If userspace supplies a value that the filter cannot support, I think it
makes more sense to return an -EINVAL here. Otherwise, the user may
believe they have enabled the filter when it is in fact now disabled.

William Breathitt Gray

> +		enable = false;
> +		length = 0;
> +	} else {
> +		enable = true;
> +		length -= 2;
> +	}
> +
> +	if (length > INTEL_QEPFLT_MAX_COUNT(length))
> +		return -EINVAL;
> +
> +	mutex_lock(&qep->lock);
> +	if (qep->enabled) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	if (enable)
> +		reg |= INTEL_QEPCON_FLT_EN;
> +	else
> +		reg &= ~INTEL_QEPCON_FLT_EN;
> +	intel_qep_writel(qep, INTEL_QEPFLT, length);
> +	intel_qep_writel(qep, INTEL_QEPCON, reg);
> +	pm_runtime_put(qep->dev);
> +	ret = len;
> +
> +out:
> +	mutex_unlock(&qep->lock);
> +	return ret;
> +}
> +
> +static ssize_t preset_enable_read(struct counter_device *counter,
> +				  struct counter_count *count,
> +				  void *priv, char *buf)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg;
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	pm_runtime_put(qep->dev);
> +	return sysfs_emit(buf, "%u\n", !(reg & INTEL_QEPCON_COUNT_RST_MODE));
> +}
> +
> +static ssize_t preset_enable_write(struct counter_device *counter,
> +				   struct counter_count *count,
> +				   void *priv, const char *buf, size_t len)
> +{
> +	struct intel_qep *qep = counter->priv;
> +	u32 reg;
> +	bool val;
> +	int ret;
> +
> +	ret = kstrtobool(buf, &val);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&qep->lock);
> +	if (qep->enabled) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	pm_runtime_get_sync(qep->dev);
> +	reg = intel_qep_readl(qep, INTEL_QEPCON);
> +	if (val)
> +		reg &= ~INTEL_QEPCON_COUNT_RST_MODE;
> +	else
> +		reg |= INTEL_QEPCON_COUNT_RST_MODE;
> +
> +	intel_qep_writel(qep, INTEL_QEPCON, reg);
> +	pm_runtime_put(qep->dev);
> +	ret = len;
> +
> +out:
> +	mutex_unlock(&qep->lock);
> +
> +	return ret;
> +}
> +
> +static const struct counter_count_ext intel_qep_count_ext[] = {
> +	INTEL_QEP_COUNTER_EXT_RW(ceiling),
> +	INTEL_QEP_COUNTER_EXT_RW(enable),
> +	INTEL_QEP_COUNTER_EXT_RW(spike_filter_ns),
> +	INTEL_QEP_COUNTER_EXT_RW(preset_enable)
> +};
> +
> +static struct counter_count intel_qep_counter_count[] = {
> +	{
> +		.id = 0,
> +		.name = "Channel 1 Count",
> +		.functions_list = intel_qep_count_functions,
> +		.num_functions = ARRAY_SIZE(intel_qep_count_functions),
> +		.synapses = intel_qep_count_synapses,
> +		.num_synapses = ARRAY_SIZE(intel_qep_count_synapses),
> +		.ext = intel_qep_count_ext,
> +		.num_ext = ARRAY_SIZE(intel_qep_count_ext),
> +	},
> +};
> +
> +static int intel_qep_probe(struct pci_dev *pci, const struct pci_device_id *id)
> +{
> +	struct intel_qep *qep;
> +	struct device *dev = &pci->dev;
> +	void __iomem *regs;
> +	int ret;
> +
> +	qep = devm_kzalloc(dev, sizeof(*qep), GFP_KERNEL);
> +	if (!qep)
> +		return -ENOMEM;
> +
> +	ret = pcim_enable_device(pci);
> +	if (ret)
> +		return ret;
> +
> +	pci_set_master(pci);
> +
> +	ret = pcim_iomap_regions(pci, BIT(0), pci_name(pci));
> +	if (ret)
> +		return ret;
> +
> +	regs = pcim_iomap_table(pci)[0];
> +	if (!regs)
> +		return -ENOMEM;
> +
> +	qep->dev = dev;
> +	qep->regs = regs;
> +	mutex_init(&qep->lock);
> +
> +	intel_qep_init(qep);
> +	pci_set_drvdata(pci, qep);
> +
> +	qep->counter.name = pci_name(pci);
> +	qep->counter.parent = dev;
> +	qep->counter.ops = &intel_qep_counter_ops;
> +	qep->counter.counts = intel_qep_counter_count;
> +	qep->counter.num_counts = ARRAY_SIZE(intel_qep_counter_count);
> +	qep->counter.signals = intel_qep_signals;
> +	qep->counter.num_signals = ARRAY_SIZE(intel_qep_signals);
> +	qep->counter.priv = qep;
> +	qep->enabled = false;
> +
> +	pm_runtime_put(dev);
> +	pm_runtime_allow(dev);
> +
> +	return devm_counter_register(&pci->dev, &qep->counter);
> +}
> +
> +static void intel_qep_remove(struct pci_dev *pci)
> +{
> +	struct intel_qep *qep = pci_get_drvdata(pci);
> +	struct device *dev = &pci->dev;
> +
> +	pm_runtime_forbid(dev);
> +	if (!qep->enabled)
> +		pm_runtime_get(dev);
> +
> +	intel_qep_writel(qep, INTEL_QEPCON, 0);
> +}
> +
> +#ifdef CONFIG_PM
> +static int intel_qep_suspend(struct device *dev)
> +{
> +	struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
> +	struct intel_qep *qep = pci_get_drvdata(pdev);
> +
> +	qep->qepcon = intel_qep_readl(qep, INTEL_QEPCON);
> +	qep->qepflt = intel_qep_readl(qep, INTEL_QEPFLT);
> +	qep->qepmax = intel_qep_readl(qep, INTEL_QEPMAX);
> +
> +	return 0;
> +}
> +
> +static int intel_qep_resume(struct device *dev)
> +{
> +	struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
> +	struct intel_qep *qep = pci_get_drvdata(pdev);
> +
> +	/*
> +	 * Make sure peripheral is disabled when restoring registers and
> +	 * control register bits that are writable only when the peripheral
> +	 * is disabled
> +	 */
> +	intel_qep_writel(qep, INTEL_QEPCON, 0);
> +	intel_qep_readl(qep, INTEL_QEPCON);
> +
> +	intel_qep_writel(qep, INTEL_QEPFLT, qep->qepflt);
> +	intel_qep_writel(qep, INTEL_QEPMAX, qep->qepmax);
> +	intel_qep_writel(qep, INTEL_QEPINT_MASK, INTEL_QEPINT_MASK_ALL);
> +
> +	/* Restore all other control register bits except enable status */
> +	intel_qep_writel(qep, INTEL_QEPCON, qep->qepcon & ~INTEL_QEPCON_EN);
> +	intel_qep_readl(qep, INTEL_QEPCON);
> +
> +	/* Restore enable status */
> +	intel_qep_writel(qep, INTEL_QEPCON, qep->qepcon);
> +
> +	return 0;
> +}
> +#endif
> +
> +static UNIVERSAL_DEV_PM_OPS(intel_qep_pm_ops,
> +			    intel_qep_suspend, intel_qep_resume, NULL);
> +
> +static const struct pci_device_id intel_qep_id_table[] = {
> +	/* EHL */
> +	{ PCI_VDEVICE(INTEL, 0x4bc3), },
> +	{ PCI_VDEVICE(INTEL, 0x4b81), },
> +	{ PCI_VDEVICE(INTEL, 0x4b82), },
> +	{ PCI_VDEVICE(INTEL, 0x4b83), },
> +	{  } /* Terminating Entry */
> +};
> +MODULE_DEVICE_TABLE(pci, intel_qep_id_table);
> +
> +static struct pci_driver intel_qep_driver = {
> +	.name = "intel-qep",
> +	.id_table = intel_qep_id_table,
> +	.probe = intel_qep_probe,
> +	.remove = intel_qep_remove,
> +	.driver = {
> +		.pm = &intel_qep_pm_ops,
> +	}
> +};
> +
> +module_pci_driver(intel_qep_driver);
> +
> +MODULE_AUTHOR("Felipe Balbi (Intel)");
> +MODULE_AUTHOR("Jarkko Nikula <jarkko.nikula@linux.intel.com>");
> +MODULE_AUTHOR("Raymond Tan <raymond.tan@intel.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Intel Quadrature Encoder Peripheral driver");
> -- 
> 2.30.2
> 

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH v2 1/2] counter: Add support for Quadrature x4 with swapped inputs

[Jarkko Nikula]

Hi

On 5/27/21 4:10 AM, William Breathitt Gray wrote:
> On Wed, May 26, 2021 at 06:06:00PM +0300, Jarkko Nikula wrote:
>> Some Quadrature Encoders can swap phase inputs A and B internally. This
>> new function will allow drivers to configure input swap mode.
>>
>> This was implemented by Felipe Balbi while he was working at Intel.
>>
>> Signed-off-by: Felipe Balbi (Intel) <balbi@kernel.org>
>> Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
> 
> There's no change in this patch from the last revision, right?
> 
> Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
> 
Yes, no changes. Will add your ack to the next version.

Jarkko

Re: [PATCH v2 2/2] counter: Add support for Intel Quadrature Encoder Peripheral

[Jarkko Nikula]

Hi

On 5/27/21 5:16 AM, William Breathitt Gray wrote:
>> +What:		/sys/bus/counter/devices/counterX/signalY/invert
>> +KernelVersion:	5.14
>> +Contact:	linux-iio@vger.kernel.org
>> +Description:
>> +		Whether signal Y inversion is enabled. Valid attribute values
>> +		are boolean.
>> +
>> +		For counter devices that have feature to control inversion of
>> +		signal Y.
> 
> I want to understand this functionality a bit better. So, this device
> has two quadrature encoder signals coming in (Phase A and Phase B) and
> this "invert" option allows the user to configure the device to invert
> these signals in hardware before before they are evaluated by the
> quadrature encoding counter. Users are able to invert each signal
> independent of the other; e.g. Phase A can be inverted, but Phase B can
> be left alone. Is my understanding correct, or is the inversion applied
> across all signals rather than just one independently?
> 
> What is the purpose of this functionality? Is this to allow users to
> adjust the direction of the count without having to physically reorient
> the encoding device (e.g. tracking counter-clockwise versus clockwise
> movement)?
> 
Yes, it's independent for each signal. Here Phase A, B and Index.

According to specification idea is to remove need for board specific 
inversion logic. Which makes me thinking this kind configuration should 
come from firmware. As well as inputs swapped function. Which is for 
correcting possible miswiring of Phase A and B signals on the board.

I'm now puzzled is there even need to have userspace visibility and 
control for these signal inversions and input swapping? Of course yes 
with my hacker hat on but for an ordinary Linux distribution point of 
view those inversions and input swapping should be set by the kernel 
automatically IMHO.

What do you think? Should I keep these sysfs attributes in the next 
version or remove them? Though I don't have plans to add firmware data 
this time. It's nice to save room for future contributions if there is a 
real need for these features :-)

>> +	return sysfs_emit(buf, "%u\n", !(reg & (uintptr_t)signal->priv));
> 
> It's easy to forget what signal->priv represents. I recommend using a
> variable to hold this value so that the logic is a bit easier to
> understand for future reviewers.
> 
Ok.

>> +static struct counter_signal intel_qep_signals[] = {
>> +	INTEL_QEP_SIGNAL(0, "Phase A", INTEL_QEPCON_EDGE_A),
>> +	INTEL_QEP_SIGNAL(1, "Phase B", INTEL_QEPCON_EDGE_A),
>> +	INTEL_QEP_SIGNAL(2, "Index", INTEL_QEPCON_EDGE_A),
> 
> Is INTEL_QEPCON_EDGE_A three times here correct, or did mean to use
> INTEL_QEPCON_EDGE_B and INTEL_QEPCON_EDGE_INDX as well?
> 
What a facepalm... last minute "lets have a nice macro here and blind 
copy-pasting" just before sending this out.

>> +	 * Spike filter length is (MAX_COUNT + 2) clock periods. Disable
>> +	 * filter when user space supplies shorter than 2 clock periods and
>> +	 * otherwise enable and set MAX_COUNT = clock periods - 2.
>> +	 */
>> +	length /= INTEL_QEP_CLK_PERIOD_NS;
>> +	if (length < 2) {
> 
> If userspace supplies a value that the filter cannot support, I think it
> makes more sense to return an -EINVAL here. Otherwise, the user may
> believe they have enabled the filter when it is in fact now disabled.
> 
Fair point. Will change.

Jarkko

Re: [PATCH v2 2/2] counter: Add support for Intel Quadrature Encoder Peripheral

[William Breathitt Gray]

[-- Attachment #1: Type: text/plain, Size: 3532 bytes --]

On Thu, May 27, 2021 at 11:14:06AM +0300, Jarkko Nikula wrote:
> Hi
> 
> On 5/27/21 5:16 AM, William Breathitt Gray wrote:
> >> +What:		/sys/bus/counter/devices/counterX/signalY/invert
> >> +KernelVersion:	5.14
> >> +Contact:	linux-iio@vger.kernel.org
> >> +Description:
> >> +		Whether signal Y inversion is enabled. Valid attribute values
> >> +		are boolean.
> >> +
> >> +		For counter devices that have feature to control inversion of
> >> +		signal Y.
> > 
> > I want to understand this functionality a bit better. So, this device
> > has two quadrature encoder signals coming in (Phase A and Phase B) and
> > this "invert" option allows the user to configure the device to invert
> > these signals in hardware before before they are evaluated by the
> > quadrature encoding counter. Users are able to invert each signal
> > independent of the other; e.g. Phase A can be inverted, but Phase B can
> > be left alone. Is my understanding correct, or is the inversion applied
> > across all signals rather than just one independently?
> > 
> > What is the purpose of this functionality? Is this to allow users to
> > adjust the direction of the count without having to physically reorient
> > the encoding device (e.g. tracking counter-clockwise versus clockwise
> > movement)?
> > 
> Yes, it's independent for each signal. Here Phase A, B and Index.
> 
> According to specification idea is to remove need for board specific 
> inversion logic. Which makes me thinking this kind configuration should 
> come from firmware. As well as inputs swapped function. Which is for 
> correcting possible miswiring of Phase A and B signals on the board.
> 
> I'm now puzzled is there even need to have userspace visibility and 
> control for these signal inversions and input swapping? Of course yes 
> with my hacker hat on but for an ordinary Linux distribution point of 
> view those inversions and input swapping should be set by the kernel 
> automatically IMHO.
> 
> What do you think? Should I keep these sysfs attributes in the next 
> version or remove them? Though I don't have plans to add firmware data 
> this time. It's nice to save room for future contributions if there is a 
> real need for these features :-)

Hi Jarkko,

Right now I'm not sure whether this inversion functionality should be
exposed to userspace as sysfs attributes in this particular way just
yet. We should be careful in introducing new sysfs attributes because
once they're released we're stuck supporting them for the indefinite
future.

Because of these reasons, I think it's best for us to err on the side of
simplicity and postpone these extensions for the future if the need
arises; we can always add them later after this driver is stabilized and
merged. For now, let's remove these sysfs attributes from the next
version and keep it simple.

> >> +static struct counter_signal intel_qep_signals[] = {
> >> +	INTEL_QEP_SIGNAL(0, "Phase A", INTEL_QEPCON_EDGE_A),
> >> +	INTEL_QEP_SIGNAL(1, "Phase B", INTEL_QEPCON_EDGE_A),
> >> +	INTEL_QEP_SIGNAL(2, "Index", INTEL_QEPCON_EDGE_A),
> > 
> > Is INTEL_QEPCON_EDGE_A three times here correct, or did mean to use
> > INTEL_QEPCON_EDGE_B and INTEL_QEPCON_EDGE_INDX as well?
> > 
> What a facepalm... last minute "lets have a nice macro here and blind 
> copy-pasting" just before sending this out.

No worries, I can ensure you I've made the same mistake as well far more
times than I care to admit. ;-)

William Breathitt Gray

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]