[PATCH v2 0/2] gpio: Generalise state persistence (was: Expose reset tolerance capability)

[PATCH v2 0/2] gpio: Generalise state persistence (was: Expose reset tolerance capability)

[Andrew Jeffery]

Hello,

This series provides an API to configure general GPIO state persistence in
gpiolib. Previously, only sleep persistence was considered, but controllers
like one found in Aspeed BMCs also support persistence of state across
controller resets. There is some prior discussion on v1[1] and the initial
RFC[2]. The only change in v2 is to rename the new pinconf property to convey
the concept of state persistence rather focussing on reset tolerance, based on
feedback from Charles Keepax[3].

Please review!

Andrew

[1] https://www.spinics.net/lists/devicetree/msg200027.html
[2] https://www.spinics.net/lists/devicetree/msg199559.html
[3] https://www.spinics.net/lists/devicetree/msg200040.html

Andrew Jeffery (2):
  gpio: gpiolib: Generalise state persistence beyond sleep
  gpio: aspeed: Add support for reset tolerance

 drivers/gpio/gpio-aspeed.c              | 39 ++++++++++++++++++++--
 drivers/gpio/gpiolib-of.c               |  6 ++--
 drivers/gpio/gpiolib-sysfs.c            | 14 +++++---
 drivers/gpio/gpiolib.c                  | 58 ++++++++++++++++++++++++++++++---
 drivers/gpio/gpiolib.h                  |  2 +-
 include/dt-bindings/gpio/gpio.h         |  6 ++--
 include/linux/gpio/consumer.h           |  8 +++++
 include/linux/gpio/machine.h            |  4 +--
 include/linux/of_gpio.h                 |  2 +-
 include/linux/pinctrl/pinconf-generic.h |  2 ++
 10 files changed, 121 insertions(+), 20 deletions(-)

-- 
2.11.0

[PATCH v2 1/2] gpio: gpiolib: Generalise state persistence beyond sleep

[Andrew Jeffery]

General support for state persistence is added to gpiolib with the
introduction of a new pinconf parameter to propagate the request to
hardware. The existing persistence support for sleep is adapted to
include hardware support if the GPIO driver provides it. Persistence
continues to be enabled by default; in-kernel consumers can opt out, but
userspace (currently) does not have a choice.

The *_SLEEP_MAY_LOSE_VALUE and *_SLEEP_MAINTAIN_VALUE symbols are
renamed, dropping the SLEEP prefix to reflect that the concept is no
longer sleep-specific.  I feel that renaming to just *_MAY_LOSE_VALUE
could initially be misinterpreted, so I've further changed the symbols
to *_TRANSITORY and *_PERSISTENT to address this.

The sysfs interface is modified only to keep consistency with the
chardev interface in enforcing persistence for userspace exports.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
 drivers/gpio/gpiolib-of.c               |  6 ++--
 drivers/gpio/gpiolib-sysfs.c            | 14 +++++---
 drivers/gpio/gpiolib.c                  | 58 ++++++++++++++++++++++++++++++---
 drivers/gpio/gpiolib.h                  |  2 +-
 include/dt-bindings/gpio/gpio.h         |  6 ++--
 include/linux/gpio/consumer.h           |  8 +++++
 include/linux/gpio/machine.h            |  4 +--
 include/linux/of_gpio.h                 |  2 +-
 include/linux/pinctrl/pinconf-generic.h |  2 ++
 9 files changed, 84 insertions(+), 18 deletions(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index e0d59e61b52f..4a2b8d3397c7 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -153,8 +153,8 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
 			*flags |= GPIO_OPEN_SOURCE;
 	}
 
-	if (of_flags & OF_GPIO_SLEEP_MAY_LOSE_VALUE)
-		*flags |= GPIO_SLEEP_MAY_LOSE_VALUE;
+	if (of_flags & OF_GPIO_TRANSITORY)
+		*flags |= GPIO_TRANSITORY;
 
 	return desc;
 }
@@ -214,6 +214,8 @@ static struct gpio_desc *of_parse_own_gpio(struct device_node *np,
 
 	if (xlate_flags & OF_GPIO_ACTIVE_LOW)
 		*lflags |= GPIO_ACTIVE_LOW;
+	if (xlate_flags & OF_GPIO_TRANSITORY)
+		*lflags |= GPIO_TRANSITORY;
 
 	if (of_property_read_bool(np, "input"))
 		*dflags |= GPIOD_IN;
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 3f454eaf2101..0bd472ffb072 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -474,11 +474,15 @@ static ssize_t export_store(struct class *class,
 			status = -ENODEV;
 		goto done;
 	}
-	status = gpiod_export(desc, true);
-	if (status < 0)
-		gpiod_free(desc);
-	else
-		set_bit(FLAG_SYSFS, &desc->flags);
+
+	status = gpiod_set_transitory(desc, false);
+	if (!status) {
+		status = gpiod_export(desc, true);
+		if (status < 0)
+			gpiod_free(desc);
+		else
+			set_bit(FLAG_SYSFS, &desc->flags);
+	}
 
 done:
 	if (status)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 3827f0767101..0d0ab5744f46 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -503,6 +503,10 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 		if (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)
 			set_bit(FLAG_OPEN_SOURCE, &desc->flags);
 
+		ret = gpiod_set_transitory(desc, false);
+		if (ret < 0)
+			goto out_free_descs;
+
 		/*
 		 * Lines have to be requested explicitly for input
 		 * or output, else the line will be treated "as is".
@@ -2424,6 +2428,46 @@ int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
 EXPORT_SYMBOL_GPL(gpiod_set_debounce);
 
 /**
+ * gpiod_set_transitory - Lose or retain GPIO state on suspend or reset
+ * @desc: descriptor of the GPIO for which to configure persistence
+ * @transitory: True to lose state on suspend or reset, false for persistence
+ *
+ * Returns:
+ * 0 on success, otherwise a negative error code.
+ */
+int gpiod_set_transitory(struct gpio_desc *desc, bool transitory)
+{
+	struct gpio_chip *chip;
+	unsigned long packed;
+	int gpio;
+	int rc;
+
+	/* Handle FLAG_TRANSITORY first for suspend case */
+	if (transitory)
+		set_bit(FLAG_TRANSITORY, &desc->flags);
+	else
+		clear_bit(FLAG_TRANSITORY, &desc->flags);
+
+	/* Configure reset persistence if the controller supports it */
+	chip = desc->gdev->chip;
+	if (!chip->set_config)
+		return 0;
+
+	packed = pinconf_to_config_packed(PIN_CONFIG_PERSIST_STATE,
+					  !transitory);
+	gpio = gpio_chip_hwgpio(desc);
+	rc = chip->set_config(chip, gpio, packed);
+	if (rc == -ENOTSUPP) {
+		dev_dbg(&desc->gdev->dev, "Reset tolerance not supported for GPIO %d\n",
+				gpio);
+		return 0;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(gpiod_set_transitory);
+
+/**
  * gpiod_is_active_low - test whether a GPIO is active-low or not
  * @desc: the gpio descriptor to test
  *
@@ -3010,8 +3054,7 @@ bool gpiochip_line_is_persistent(struct gpio_chip *chip, unsigned int offset)
 	if (offset >= chip->ngpio)
 		return false;
 
-	return !test_bit(FLAG_SLEEP_MAY_LOSE_VALUE,
-			 &chip->gpiodev->descs[offset].flags);
+	return !test_bit(FLAG_TRANSITORY, &chip->gpiodev->descs[offset].flags);
 }
 EXPORT_SYMBOL_GPL(gpiochip_line_is_persistent);
 
@@ -3435,8 +3478,10 @@ int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
 		set_bit(FLAG_OPEN_DRAIN, &desc->flags);
 	if (lflags & GPIO_OPEN_SOURCE)
 		set_bit(FLAG_OPEN_SOURCE, &desc->flags);
-	if (lflags & GPIO_SLEEP_MAY_LOSE_VALUE)
-		set_bit(FLAG_SLEEP_MAY_LOSE_VALUE, &desc->flags);
+
+	status = gpiod_set_transitory(desc, (lflags & GPIO_TRANSITORY));
+	if (status < 0)
+		return status;
 
 	/* No particular flag request, return here... */
 	if (!(dflags & GPIOD_FLAGS_BIT_DIR_SET)) {
@@ -3550,6 +3595,7 @@ struct gpio_desc *fwnode_get_named_gpiod(struct fwnode_handle *fwnode,
 	bool active_low = false;
 	bool single_ended = false;
 	bool open_drain = false;
+	bool transitory = false;
 	int ret;
 
 	if (!fwnode)
@@ -3564,6 +3610,7 @@ struct gpio_desc *fwnode_get_named_gpiod(struct fwnode_handle *fwnode,
 			active_low = flags & OF_GPIO_ACTIVE_LOW;
 			single_ended = flags & OF_GPIO_SINGLE_ENDED;
 			open_drain = flags & OF_GPIO_OPEN_DRAIN;
+			transitory = flags & OF_GPIO_TRANSITORY;
 		}
 	} else if (is_acpi_node(fwnode)) {
 		struct acpi_gpio_info info;
@@ -3594,6 +3641,9 @@ struct gpio_desc *fwnode_get_named_gpiod(struct fwnode_handle *fwnode,
 			lflags |= GPIO_OPEN_SOURCE;
 	}
 
+	if (transitory)
+		lflags |= GPIO_TRANSITORY;
+
 	ret = gpiod_configure_flags(desc, propname, lflags, dflags);
 	if (ret < 0) {
 		gpiod_put(desc);
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index af48322839c3..736b189d1bb5 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -205,7 +205,7 @@ struct gpio_desc {
 #define FLAG_OPEN_SOURCE 8	/* Gpio is open source type */
 #define FLAG_USED_AS_IRQ 9	/* GPIO is connected to an IRQ */
 #define FLAG_IS_HOGGED	11	/* GPIO is hogged */
-#define FLAG_SLEEP_MAY_LOSE_VALUE 12	/* GPIO may lose value in sleep */
+#define FLAG_TRANSITORY 12	/* GPIO may lose value in sleep or reset */
 
 	/* Connection label */
 	const char		*label;
diff --git a/include/dt-bindings/gpio/gpio.h b/include/dt-bindings/gpio/gpio.h
index 70de5b7a6c9b..43dc230d3921 100644
--- a/include/dt-bindings/gpio/gpio.h
+++ b/include/dt-bindings/gpio/gpio.h
@@ -28,8 +28,8 @@
 #define GPIO_OPEN_DRAIN (GPIO_SINGLE_ENDED | GPIO_LINE_OPEN_DRAIN)
 #define GPIO_OPEN_SOURCE (GPIO_SINGLE_ENDED | GPIO_LINE_OPEN_SOURCE)
 
-/* Bit 3 express GPIO suspend/resume persistence */
-#define GPIO_SLEEP_MAINTAIN_VALUE 0
-#define GPIO_SLEEP_MAY_LOSE_VALUE 8
+/* Bit 3 express GPIO suspend/resume and reset persistence */
+#define GPIO_PERSISTENT 0
+#define GPIO_TRANSITORY 8
 
 #endif
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index d4920ec1f1da..d77e88c96f38 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -132,6 +132,7 @@ void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
 					int *value_array);
 
 int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce);
+int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);
 
 int gpiod_is_active_low(const struct gpio_desc *desc);
 int gpiod_cansleep(const struct gpio_desc *desc);
@@ -424,6 +425,13 @@ static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
 	return -ENOSYS;
 }
 
+static inline int gpiod_set_transitory(struct gpio_desc *desc, bool transitory)
+{
+	/* GPIO can never have been requested */
+	WARN_ON(1);
+	return -ENOSYS;
+}
+
 static inline int gpiod_is_active_low(const struct gpio_desc *desc)
 {
 	/* GPIO can never have been requested */
diff --git a/include/linux/gpio/machine.h b/include/linux/gpio/machine.h
index 5e9f294c29eb..33a97ede6404 100644
--- a/include/linux/gpio/machine.h
+++ b/include/linux/gpio/machine.h
@@ -9,8 +9,8 @@ enum gpio_lookup_flags {
 	GPIO_ACTIVE_LOW = (1 << 0),
 	GPIO_OPEN_DRAIN = (1 << 1),
 	GPIO_OPEN_SOURCE = (1 << 2),
-	GPIO_SLEEP_MAINTAIN_VALUE = (0 << 3),
-	GPIO_SLEEP_MAY_LOSE_VALUE = (1 << 3),
+	GPIO_PERSISTENT = (0 << 3),
+	GPIO_TRANSITORY = (1 << 3),
 };
 
 /**
diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h
index 1fe205582111..18a7f03e1182 100644
--- a/include/linux/of_gpio.h
+++ b/include/linux/of_gpio.h
@@ -31,7 +31,7 @@ enum of_gpio_flags {
 	OF_GPIO_ACTIVE_LOW = 0x1,
 	OF_GPIO_SINGLE_ENDED = 0x2,
 	OF_GPIO_OPEN_DRAIN = 0x4,
-	OF_GPIO_SLEEP_MAY_LOSE_VALUE = 0x8,
+	OF_GPIO_TRANSITORY = 0x8,
 };
 
 #ifdef CONFIG_OF_GPIO
diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
index 5d8bc7f21c2a..824094f39ad2 100644
--- a/include/linux/pinctrl/pinconf-generic.h
+++ b/include/linux/pinctrl/pinconf-generic.h
@@ -90,6 +90,7 @@
  * @PIN_CONFIG_SLEW_RATE: if the pin can select slew rate, the argument to
  *	this parameter (on a custom format) tells the driver which alternative
  *	slew rate to use.
+ * @PIN_CONFIG_PERSIST_STATE: retain pin state across sleep or controller reset
  * @PIN_CONFIG_END: this is the last enumerator for pin configurations, if
  *	you need to pass in custom configurations to the pin controller, use
  *	PIN_CONFIG_END+1 as the base offset.
@@ -117,6 +118,7 @@ enum pin_config_param {
 	PIN_CONFIG_POWER_SOURCE,
 	PIN_CONFIG_SLEEP_HARDWARE_STATE,
 	PIN_CONFIG_SLEW_RATE,
+	PIN_CONFIG_PERSIST_STATE,
 	PIN_CONFIG_END = 0x7F,
 	PIN_CONFIG_MAX = 0xFF,
 };
-- 
2.11.0

[PATCH v2 2/2] gpio: aspeed: Add support for reset tolerance

[Andrew Jeffery]

Use the new pinconf parameter for state persistence to expose the
associated capability of the Aspeed GPIO controller.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
---
 drivers/gpio/gpio-aspeed.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-aspeed.c b/drivers/gpio/gpio-aspeed.c
index 00dc1c020198..3125dcb9211d 100644
--- a/drivers/gpio/gpio-aspeed.c
+++ b/drivers/gpio/gpio-aspeed.c
@@ -60,6 +60,7 @@ struct aspeed_gpio_bank {
 	uint16_t	val_regs;
 	uint16_t	irq_regs;
 	uint16_t	debounce_regs;
+	uint16_t	tolerance_regs;
 	const char	names[4][3];
 };
 
@@ -70,48 +71,56 @@ static const struct aspeed_gpio_bank aspeed_gpio_banks[] = {
 		.val_regs = 0x0000,
 		.irq_regs = 0x0008,
 		.debounce_regs = 0x0040,
+		.tolerance_regs = 0x001c,
 		.names = { "A", "B", "C", "D" },
 	},
 	{
 		.val_regs = 0x0020,
 		.irq_regs = 0x0028,
 		.debounce_regs = 0x0048,
+		.tolerance_regs = 0x003c,
 		.names = { "E", "F", "G", "H" },
 	},
 	{
 		.val_regs = 0x0070,
 		.irq_regs = 0x0098,
 		.debounce_regs = 0x00b0,
+		.tolerance_regs = 0x00ac,
 		.names = { "I", "J", "K", "L" },
 	},
 	{
 		.val_regs = 0x0078,
 		.irq_regs = 0x00e8,
 		.debounce_regs = 0x0100,
+		.tolerance_regs = 0x00fc,
 		.names = { "M", "N", "O", "P" },
 	},
 	{
 		.val_regs = 0x0080,
 		.irq_regs = 0x0118,
 		.debounce_regs = 0x0130,
+		.tolerance_regs = 0x012c,
 		.names = { "Q", "R", "S", "T" },
 	},
 	{
 		.val_regs = 0x0088,
 		.irq_regs = 0x0148,
 		.debounce_regs = 0x0160,
+		.tolerance_regs = 0x015c,
 		.names = { "U", "V", "W", "X" },
 	},
 	{
 		.val_regs = 0x01E0,
 		.irq_regs = 0x0178,
 		.debounce_regs = 0x0190,
+		.tolerance_regs = 0x018c,
 		.names = { "Y", "Z", "AA", "AB" },
 	},
 	{
-		.val_regs = 0x01E8,
-		.irq_regs = 0x01A8,
+		.val_regs = 0x01e8,
+		.irq_regs = 0x01a8,
 		.debounce_regs = 0x01c0,
+		.tolerance_regs = 0x01bc,
 		.names = { "AC", "", "", "" },
 	},
 };
@@ -534,6 +543,30 @@ static int aspeed_gpio_setup_irqs(struct aspeed_gpio *gpio,
 	return 0;
 }
 
+static int aspeed_gpio_reset_tolerance(struct gpio_chip *chip,
+					unsigned int offset, bool enable)
+{
+	struct aspeed_gpio *gpio = gpiochip_get_data(chip);
+	const struct aspeed_gpio_bank *bank;
+	unsigned long flags;
+	u32 val;
+
+	bank = to_bank(offset);
+
+	spin_lock_irqsave(&gpio->lock, flags);
+	val = readl(gpio->base + bank->tolerance_regs);
+
+	if (enable)
+		val |= GPIO_BIT(offset);
+	else
+		val &= ~GPIO_BIT(offset);
+
+	writel(val, gpio->base + bank->tolerance_regs);
+	spin_unlock_irqrestore(&gpio->lock, flags);
+
+	return 0;
+}
+
 static int aspeed_gpio_request(struct gpio_chip *chip, unsigned int offset)
 {
 	if (!have_gpio(gpiochip_get_data(chip), offset))
@@ -771,6 +804,8 @@ static int aspeed_gpio_set_config(struct gpio_chip *chip, unsigned int offset,
 			param == PIN_CONFIG_DRIVE_OPEN_SOURCE)
 		/* Return -ENOTSUPP to trigger emulation, as per datasheet */
 		return -ENOTSUPP;
+	else if (param == PIN_CONFIG_PERSIST_STATE)
+		return aspeed_gpio_reset_tolerance(chip, offset, arg);
 
 	return -ENOTSUPP;
 }
-- 
2.11.0

Re: [PATCH v2 1/2] gpio: gpiolib: Generalise state persistence beyond sleep

[Charles Keepax]

On Mon, Oct 30, 2017 at 04:52:17PM +1030, Andrew Jeffery wrote:
> General support for state persistence is added to gpiolib with the
> introduction of a new pinconf parameter to propagate the request to
> hardware. The existing persistence support for sleep is adapted to
> include hardware support if the GPIO driver provides it. Persistence
> continues to be enabled by default; in-kernel consumers can opt out, but
> userspace (currently) does not have a choice.
> 
> The *_SLEEP_MAY_LOSE_VALUE and *_SLEEP_MAINTAIN_VALUE symbols are
> renamed, dropping the SLEEP prefix to reflect that the concept is no
> longer sleep-specific.  I feel that renaming to just *_MAY_LOSE_VALUE
> could initially be misinterpreted, so I've further changed the symbols
> to *_TRANSITORY and *_PERSISTENT to address this.
> 
> The sysfs interface is modified only to keep consistency with the
> chardev interface in enforcing persistence for userspace exports.
> 
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> ---
>  /**
> + * gpiod_set_transitory - Lose or retain GPIO state on suspend or reset
> + * @desc: descriptor of the GPIO for which to configure persistence
> + * @transitory: True to lose state on suspend or reset, false for persistence
> + *
> + * Returns:
> + * 0 on success, otherwise a negative error code.
> + */
> +int gpiod_set_transitory(struct gpio_desc *desc, bool transitory)
> +{
> +	struct gpio_chip *chip;
> +	unsigned long packed;
> +	int gpio;
> +	int rc;
> +
> +	/* Handle FLAG_TRANSITORY first for suspend case */
> +	if (transitory)
> +		set_bit(FLAG_TRANSITORY, &desc->flags);
> +	else
> +		clear_bit(FLAG_TRANSITORY, &desc->flags);
> +
> +	/* Configure reset persistence if the controller supports it */

This comment could use an update.

> +	chip = desc->gdev->chip;
> +	if (!chip->set_config)
> +		return 0;
> +
> +	packed = pinconf_to_config_packed(PIN_CONFIG_PERSIST_STATE,
> +					  !transitory);
> +	gpio = gpio_chip_hwgpio(desc);
> +	rc = chip->set_config(chip, gpio, packed);
> +	if (rc == -ENOTSUPP) {
> +		dev_dbg(&desc->gdev->dev, "Reset tolerance not supported for GPIO %d\n",
> +				gpio);

And this debug message.

> +		return 0;
> +	}
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(gpiod_set_transitory);
> +

Otherwise think this all looks good to me.

Thanks,
Charles