[PATCH v3 0/6] drm: Prepare to use a GPIO on ti-sn65dsi86 for Hot Plug Detect

[PATCH v3 0/6] drm: Prepare to use a GPIO on ti-sn65dsi86 for Hot Plug Detect

[Douglas Anderson]

As talked about in commit c2bfc223882d ("drm/bridge: ti-sn65dsi86:
Remove the mystery delay"), the normal HPD pin on ti-sn65dsi86 is
kinda useless, at least for embedded DisplayPort (eDP).  However,
despite the fact that the actual HPD pin on the bridge is mostly
useless for eDP, the concept of HPD for eDP still makes sense.  It
allows us to optimize out a hardcoded delay that many panels need if
HPD isn't hooked up.  Panel timing diagrams show HPD as one of the
events to measure timing from and we have to assume the worst case if
we can't actually read HPD.

One way to use HPD for eDP without using the mostly useless HPD pin on
ti-sn65dsi86 is to route the panel's HPD somewhere else in the system,
like to a GPIO.  This works great because eDP panels aren't physically
hotplugged.  That means the debouncing logic that caused us problems
wasn't really needed and a raw GPIO works great.

As per the above, a smart board designer would realize the value of
HPD and choose to route it to a GPIO somewhere on the board to avoid
the silly sn65dsi86 debouncing.  While said "smart designer" could
theoretically route HPD anywhere on the board, a really smart designer
would realize that there are several GPIOs on the bridge itself that
are nearly useless for anything but this purpose and route HPD to one
of those.

This series of patches is intended to allow the scenario described
above.

This patch has been tested on a board that is not yet mainline.  On
the hardware I have:
- Panel spec says HPD could take up to 200 ms to come up, so without
  HPD hooked up we need to delay 200 ms.
- On my board the panel is powered by the same rail as the
  touchscreen.  By chance of probe order the touchscreen comes up
  first.  This means by the time we check HPD in ti_sn_bridge_enable()
  it's already up.  Thus we can use the panel on 200 ms earlier.
- If I measure HPD on this pane it comes up ~56 ms after the panel is
  powered.  This means I can save 144 ms of delay.

Side effects (though not main goals) of this series are:
- ti-sn65dsi86 GPIOs are now exported in Linux.
- ti-sn65dsi86 bindings are converted to yaml.
- Common panel bindings now have "hpd-gpios" listed.
- The simple-panel driver in Linux can delay in prepare based on
  "hpd-gpios"
- ti-sn65dsi86 bindings (and current user) now specifies "no-hpd"
  if HPD isn't hooked up.

Changes in v3:
- Becaue => Because
- Add a kernel-doc to our pdata to clarify double-duty of gchip_output.
- More comments about how powering off affects us (get_dir, dir_input).
- Cleanup tail of ti_sn_setup_gpio_controller() to avoid one "return".
- Use a bitmap rather than rolling my own.
- Remind how gpio_get_optional() works in the commit message.
- useful implement => useful to implement

Changes in v2:
- ("Export...GPIOs") is 1/2 of replacement for ("Allow...bridge GPIOs")
- ("dt-bindings: display: Add hpd-gpios to panel-common...") new for v2
- ("simple...hpd-gpios") is 1/2 of replacement for ("Allow...bridge GPIOs")
- specification => specifier.
- power up => power.
- Added back missing suspend-gpios.
- data-lanes and lane-polarities are are the right place now.
- endpoints don't need to be patternProperties.
- Specified more details for data-lanes and lane-polarities.
- Added old example back in, fixing bugs in it.
- Example i2c bus is just called "i2c", not "i2c1" now.
- ("dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd") new for v2.
- ("arm64: dts: sdm845: Add "no-hpd" to sn65dsi86 on cheza") new for v2.

Douglas Anderson (6):
  drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux
  dt-bindings: display: Add hpd-gpios to panel-common bindings
  drm/panel-simple: Support hpd-gpios for delaying prepare()
  dt-bindings: drm/bridge: ti-sn65dsi86: Convert to yaml
  dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd
  arm64: dts: sdm845: Add "no-hpd" to sn65dsi86 on cheza

 .../bindings/display/bridge/ti,sn65dsi86.txt  |  87 ------
 .../bindings/display/bridge/ti,sn65dsi86.yaml | 285 ++++++++++++++++++
 .../bindings/display/panel/panel-common.yaml  |   6 +
 arch/arm64/boot/dts/qcom/sdm845-cheza.dtsi    |   2 +
 drivers/gpu/drm/bridge/ti-sn65dsi86.c         | 194 ++++++++++++
 drivers/gpu/drm/panel/panel-simple.c          |  53 ++++
 6 files changed, 540 insertions(+), 87 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt
 create mode 100644 Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml

-- 
2.26.1.301.g55bc3eb7cb9-goog

[PATCH v3 1/6] drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux

[Douglas Anderson]

The ti-sn65dsi86 MIPI DSI to eDP bridge chip has 4 pins on it that can
be used as GPIOs in a system.  Each pin can be configured as input,
output, or a special function for the bridge chip.  These are:
- GPIO1: SUSPEND Input
- GPIO2: DSIA VSYNC
- GPIO3: DSIA HSYNC or VSYNC
- GPIO4: PWM

Let's expose these pins as GPIOs.  A few notes:
- Access to ti-sn65dsi86 is via i2c so we set "can_sleep".
- These pins can't be configured for IRQ.
- There are no programmable pulls or other fancy features.
- Keeping the bridge chip powered might be expensive.  The driver is
  setup such that if all used GPIOs are only inputs we'll power the
  bridge chip on just long enough to read the GPIO and then power it
  off again.  Setting a GPIO as output will keep the bridge powered.
- If someone releases a GPIO we'll implicitly switch it to an input so
  we no longer need to keep the bridge powered for it.

Because of all of the above limitations we just need to implement a
bare-bones GPIO driver.  The device tree bindings already account for
this device being a GPIO controller so we only need the driver changes
for it.

NOTE: Despite the fact that these pins are nominally muxable I don't
believe it makes sense to expose them through the pinctrl interface as
well as the GPIO interface.  The special functions are things that the
bridge chip driver itself would care about and it can just configure
the pins as needed.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---

Changes in v3:
- Becaue => Because
- Add a kernel-doc to our pdata to clarify double-duty of gchip_output.
- More comments about how powering off affects us (get_dir, dir_input).
- Cleanup tail of ti_sn_setup_gpio_controller() to avoid one "return".
- Use a bitmap rather than rolling my own.

Changes in v2:
- ("Export...GPIOs") is 1/2 of replacement for ("Allow...bridge GPIOs")

 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 194 ++++++++++++++++++++++++++
 1 file changed, 194 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index 6ad688b320ae..fcd817835c43 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -7,6 +7,8 @@
 #include <linux/clk.h>
 #include <linux/debugfs.h>
 #include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio.h>
 #include <linux/i2c.h>
 #include <linux/iopoll.h>
 #include <linux/module.h>
@@ -54,6 +56,13 @@
 #define  BPP_18_RGB				BIT(0)
 #define SN_HPD_DISABLE_REG			0x5C
 #define  HPD_DISABLE				BIT(0)
+#define SN_GPIO_IO_REG				0x5E
+#define  SN_GPIO_INPUT_SHIFT			4
+#define  SN_GPIO_OUTPUT_SHIFT			0
+#define SN_GPIO_CTRL_REG			0x5F
+#define  SN_GPIO_MUX_INPUT			0
+#define  SN_GPIO_MUX_OUTPUT			1
+#define  SN_GPIO_MUX_SPECIAL			2
 #define SN_AUX_WDATA_REG(x)			(0x64 + (x))
 #define SN_AUX_ADDR_19_16_REG			0x74
 #define SN_AUX_ADDR_15_8_REG			0x75
@@ -88,6 +97,31 @@
 
 #define SN_REGULATOR_SUPPLY_NUM		4
 
+#define SN_NUM_GPIOS			4
+
+/**
+ * struct ti_sn_bridge - Platform data for ti-sn65dsi86 driver.
+ * @dev:          Pointer to our device.
+ * @regmap:       Regmap for accessing i2c.
+ * @aux:          Our aux channel.
+ * @bridge:       Our bridge.
+ * @connector:    Our connector.
+ * @debugfs:      Used for managing our debugfs.
+ * @host_node:    Remote DSI node.
+ * @dsi:          Our MIPI DSI source.
+ * @refclk:       Our reference clock.
+ * @panel:        Our panel.
+ * @enable_gpio:  The GPIO we toggle to enable the bridge.
+ * @supplies:     Data for bulk enabling/disabling our regulators.
+ * @dp_lanes:     Count of dp_lanes we're using.
+ *
+ * @gchip:        If we expose our GPIOs, this is used.
+ * @gchip_output: A cache of whether we've set GPIOs to output.  This
+ *                serves double-duty of keeping track of the direction and
+ *                also keeping track of whether we've incremented the
+ *                pm_runtime reference count for this pin, which we do
+ *                whenever a pin is configured as an output.
+ */
 struct ti_sn_bridge {
 	struct device			*dev;
 	struct regmap			*regmap;
@@ -102,6 +136,9 @@ struct ti_sn_bridge {
 	struct gpio_desc		*enable_gpio;
 	struct regulator_bulk_data	supplies[SN_REGULATOR_SUPPLY_NUM];
 	int				dp_lanes;
+
+	struct gpio_chip		gchip;
+	DECLARE_BITMAP(gchip_output, SN_NUM_GPIOS);
 };
 
 static const struct regmap_range ti_sn_bridge_volatile_ranges[] = {
@@ -874,6 +911,157 @@ static int ti_sn_bridge_parse_dsi_host(struct ti_sn_bridge *pdata)
 	return 0;
 }
 
+static struct ti_sn_bridge *gchip_to_pdata(struct gpio_chip *chip)
+{
+	return container_of(chip, struct ti_sn_bridge, gchip);
+}
+
+static int ti_sn_bridge_gpio_get_direction(struct gpio_chip *chip,
+					   unsigned int offset)
+{
+	struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
+
+	/*
+	 * We already have to keep track of the direction because we use
+	 * that to figure out whether we've powered the device.  We can
+	 * just return that rather than (maybe) powering up the device
+	 * to ask its direction.
+	 */
+	return test_bit(offset, pdata->gchip_output) ?
+		GPIOF_DIR_OUT : GPIOF_DIR_IN;
+}
+
+static int ti_sn_bridge_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
+	unsigned int val;
+	int ret;
+
+	/*
+	 * When the pin is an input we don't forcibly keep the bridge
+	 * powered--we just power it on to read the pin.  NOTE: part of
+	 * the reason this works is that the bridge defaults (when
+	 * powered back on) to all 4 GPIOs being configured as GPIO input.
+	 * Also note that if something else is keeping the chip powered the
+	 * pm_runtime functions are lightweight increments of a refcount.
+	 */
+	pm_runtime_get_sync(pdata->dev);
+	ret = regmap_read(pdata->regmap, SN_GPIO_IO_REG, &val);
+	pm_runtime_put(pdata->dev);
+
+	if (ret)
+		return ret;
+
+	return (val >> (SN_GPIO_INPUT_SHIFT + offset)) & 1;
+}
+
+static void ti_sn_bridge_gpio_set(struct gpio_chip *chip, unsigned int offset,
+				  int val)
+{
+	struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
+	int ret;
+
+	if (!test_bit(offset, pdata->gchip_output)) {
+		dev_err(pdata->dev, "Ignoring GPIO set while input\n");
+		return;
+	}
+
+	val &= 1;
+	ret = regmap_update_bits(pdata->regmap, SN_GPIO_IO_REG,
+				 BIT(SN_GPIO_OUTPUT_SHIFT + offset),
+				 val << (SN_GPIO_OUTPUT_SHIFT + offset));
+}
+
+static int ti_sn_bridge_gpio_direction_input(struct gpio_chip *chip,
+					     unsigned int offset)
+{
+	struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
+	int shift = offset * 2;
+	int ret;
+
+	if (!test_and_clear_bit(offset, pdata->gchip_output))
+		return 0;
+
+	ret = regmap_update_bits(pdata->regmap, SN_GPIO_CTRL_REG,
+				 0x3 << shift, SN_GPIO_MUX_INPUT << shift);
+	if (ret) {
+		set_bit(offset, pdata->gchip_output);
+		return ret;
+	}
+
+	/*
+	 * NOTE: if nobody else is powering the device this may fully power
+	 * it off and when it comes back it will have lost all state, but
+	 * that's OK because the default is input and we're now an input.
+	 */
+	pm_runtime_put(pdata->dev);
+
+	return 0;
+}
+
+static int ti_sn_bridge_gpio_direction_output(struct gpio_chip *chip,
+					      unsigned int offset, int val)
+{
+	struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
+	int shift = offset * 2;
+	int ret;
+
+	if (test_and_set_bit(offset, pdata->gchip_output))
+		return 0;
+
+	pm_runtime_get_sync(pdata->dev);
+
+	/* Set value first to avoid glitching */
+	ti_sn_bridge_gpio_set(chip, offset, val);
+
+	/* Set direction */
+	ret = regmap_update_bits(pdata->regmap, SN_GPIO_CTRL_REG,
+				 0x3 << shift, SN_GPIO_MUX_OUTPUT << shift);
+	if (ret) {
+		clear_bit(offset, pdata->gchip_output);
+		pm_runtime_put(pdata->dev);
+	}
+
+	return ret;
+}
+
+static void ti_sn_bridge_gpio_free(struct gpio_chip *chip, unsigned int offset)
+{
+	/* We won't keep pm_runtime if we're input, so switch there on free */
+	ti_sn_bridge_gpio_direction_input(chip, offset);
+}
+
+static const char * const ti_sn_bridge_gpio_names[SN_NUM_GPIOS] = {
+	"GPIO1", "GPIO2", "GPIO3", "GPIO4"
+};
+
+static int ti_sn_setup_gpio_controller(struct ti_sn_bridge *pdata)
+{
+	int ret;
+
+	/* Only init if someone is going to use us as a GPIO controller */
+	if (!of_property_read_bool(pdata->dev->of_node, "gpio-controller"))
+		return 0;
+
+	pdata->gchip.label = dev_name(pdata->dev);
+	pdata->gchip.parent = pdata->dev;
+	pdata->gchip.owner = THIS_MODULE;
+	pdata->gchip.free = ti_sn_bridge_gpio_free;
+	pdata->gchip.get_direction = ti_sn_bridge_gpio_get_direction;
+	pdata->gchip.direction_input = ti_sn_bridge_gpio_direction_input;
+	pdata->gchip.direction_output = ti_sn_bridge_gpio_direction_output;
+	pdata->gchip.get = ti_sn_bridge_gpio_get;
+	pdata->gchip.set = ti_sn_bridge_gpio_set;
+	pdata->gchip.can_sleep = true;
+	pdata->gchip.names = ti_sn_bridge_gpio_names;
+	pdata->gchip.ngpio = SN_NUM_GPIOS;
+	ret = devm_gpiochip_add_data(pdata->dev, &pdata->gchip, pdata);
+	if (ret)
+		dev_err(pdata->dev, "can't add gpio chip\n");
+
+	return ret;
+}
+
 static int ti_sn_bridge_probe(struct i2c_client *client,
 			      const struct i2c_device_id *id)
 {
@@ -937,6 +1125,12 @@ static int ti_sn_bridge_probe(struct i2c_client *client,
 
 	pm_runtime_enable(pdata->dev);
 
+	ret = ti_sn_setup_gpio_controller(pdata);
+	if (ret) {
+		pm_runtime_disable(pdata->dev);
+		return ret;
+	}
+
 	i2c_set_clientdata(client, pdata);
 
 	pdata->aux.name = "ti-sn65dsi86-aux";
-- 
2.26.1.301.g55bc3eb7cb9-goog

[PATCH v3 2/6] dt-bindings: display: Add hpd-gpios to panel-common bindings

[Douglas Anderson]

In the cases where there is no connector in a system there's no great
place to put "hpd-gpios".  As per discussion [1] the best place to put
it is in the panel.  Add this to the device tree bindings.

[1] https://lore.kernel.org/r/20200417180819.GE5861@pendragon.ideasonboard.com

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
---

Changes in v3: None
Changes in v2:
- ("dt-bindings: display: Add hpd-gpios to panel-common...") new for v2

 .../devicetree/bindings/display/panel/panel-common.yaml     | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/panel/panel-common.yaml b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
index ed051ba12084..e9a04a3a4f5f 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-common.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
@@ -96,6 +96,12 @@ properties:
       (hot plug detect) signal, but the signal isn't hooked up so we should
       hardcode the max delay from the panel spec when powering up the panel.
 
+  hpd-gpios:
+    maxItems: 1
+    description:
+      If Hot Plug Detect (HPD) is connected to a GPIO in the system rather
+      than a dedicated HPD pin the pin can be specified here.
+
   # Control I/Os
 
   # Many display panels can be controlled through pins driven by GPIOs. The nature
-- 
2.26.1.301.g55bc3eb7cb9-goog

[PATCH v3 3/6] drm/panel-simple: Support hpd-gpios for delaying prepare()

[Douglas Anderson]

People use panel-simple when they have panels that are builtin to
their device.  In these cases the HPD (Hot Plug Detect) signal isn't
really used for hotplugging devices but instead is used for power
sequencing.  Panel timing diagrams (especially for eDP panels) usually
have the HPD signal in them and it acts as an indicator that the panel
is ready for us to talk to it.

Sometimes the HPD signal is hooked up to a normal GPIO on a system.
In this case we need to poll it in the correct place to know that the
panel is ready for us.  In some system designs the right place for
this is panel-simple.

When adding this support, we'll account for the case that there might
be a circular dependency between panel-simple and the provider of the
GPIO.  The case this was designed for was for the "ti-sn65dsi86"
bridge chip.  If HPD is hooked up to one of the GPIOs provided by the
bridge chip then in our probe function we'll always get back
-EPROBE_DEFER.  Let's handle this by allowing this GPIO to show up
late if we saw -EPROBE_DEFER during probe.  NOTE: since the
gpio_get_optional() is used, if the "hpd-gpios" isn't there our
variable will just be NULL and we won't do anything in prepare().

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
---

Changes in v3:
- Remind how gpio_get_optional() works in the commit message.

Changes in v2:
- ("simple...hpd-gpios") is 1/2 of replacement for ("Allow...bridge GPIOs")

 drivers/gpu/drm/panel/panel-simple.c | 53 ++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 3ad828eaefe1..f816e2aa29cd 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -23,6 +23,7 @@
 
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
@@ -108,6 +109,7 @@ struct panel_simple {
 	struct i2c_adapter *ddc;
 
 	struct gpio_desc *enable_gpio;
+	struct gpio_desc *hpd_gpio;
 
 	struct drm_display_mode override_mode;
 };
@@ -259,11 +261,37 @@ static int panel_simple_unprepare(struct drm_panel *panel)
 	return 0;
 }
 
+static int panel_simple_get_hpd_gpio(struct device *dev,
+				     struct panel_simple *p, bool from_probe)
+{
+	int err;
+
+	p->hpd_gpio = devm_gpiod_get_optional(dev, "hpd", GPIOD_IN);
+	if (IS_ERR(p->hpd_gpio)) {
+		err = PTR_ERR(p->hpd_gpio);
+
+		/*
+		 * If we're called from probe we won't consider '-EPROBE_DEFER'
+		 * to be an error--we'll leave the error code in "hpd_gpio".
+		 * When we try to use it we'll try again.  This allows for
+		 * circular dependencies where the component providing the
+		 * hpd gpio needs the panel to init before probing.
+		 */
+		if (err != -EPROBE_DEFER || !from_probe) {
+			dev_err(dev, "failed to get 'hpd' GPIO: %d\n", err);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
 static int panel_simple_prepare(struct drm_panel *panel)
 {
 	struct panel_simple *p = to_panel_simple(panel);
 	unsigned int delay;
 	int err;
+	int hpd_asserted;
 
 	if (p->prepared)
 		return 0;
@@ -282,6 +310,26 @@ static int panel_simple_prepare(struct drm_panel *panel)
 	if (delay)
 		msleep(delay);
 
+	if (p->hpd_gpio) {
+		if (IS_ERR(p->hpd_gpio)) {
+			err = panel_simple_get_hpd_gpio(panel->dev, p, false);
+			if (err)
+				return err;
+		}
+
+		err = readx_poll_timeout(gpiod_get_value_cansleep, p->hpd_gpio,
+					 hpd_asserted, hpd_asserted,
+					 1000, 2000000);
+		if (hpd_asserted < 0)
+			err = hpd_asserted;
+
+		if (err) {
+			dev_err(panel->dev,
+				"error waiting for hpd GPIO: %d\n", err);
+			return err;
+		}
+	}
+
 	p->prepared = true;
 
 	return 0;
@@ -462,6 +510,11 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 	panel->desc = desc;
 
 	panel->no_hpd = of_property_read_bool(dev->of_node, "no-hpd");
+	if (!panel->no_hpd) {
+		err = panel_simple_get_hpd_gpio(dev, panel, true);
+		if (err)
+			return err;
+	}
 
 	panel->supply = devm_regulator_get(dev, "power");
 	if (IS_ERR(panel->supply))
-- 
2.26.1.301.g55bc3eb7cb9-goog

[PATCH v3 4/6] dt-bindings: drm/bridge: ti-sn65dsi86: Convert to yaml

[Douglas Anderson]

This moves the bindings over, based a lot on toshiba,tc358768.yaml.
Unless there's someone known to be better, I've set the maintainer in
the yaml as the first person to submit bindings.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v3: None
Changes in v2:
- specification => specifier.
- power up => power.
- Added back missing suspend-gpios.
- data-lanes and lane-polarities are are the right place now.
- endpoints don't need to be patternProperties.
- Specified more details for data-lanes and lane-polarities.
- Added old example back in, fixing bugs in it.
- Example i2c bus is just called "i2c", not "i2c1" now.

 .../bindings/display/bridge/ti,sn65dsi86.txt  |  87 ------
 .../bindings/display/bridge/ti,sn65dsi86.yaml | 279 ++++++++++++++++++
 2 files changed, 279 insertions(+), 87 deletions(-)
 delete mode 100644 Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt
 create mode 100644 Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml

diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt
deleted file mode 100644
index 8ec4a7f2623a..000000000000
--- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt
+++ /dev/null
@@ -1,87 +0,0 @@
-SN65DSI86 DSI to eDP bridge chip
---------------------------------
-
-This is the binding for Texas Instruments SN65DSI86 bridge.
-http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=sn65dsi86&fileType=pdf
-
-Required properties:
-- compatible: Must be "ti,sn65dsi86"
-- reg: i2c address of the chip, 0x2d as per datasheet
-- enable-gpios: gpio specification for bridge_en pin (active high)
-
-- vccio-supply: A 1.8V supply that powers up the digital IOs.
-- vpll-supply: A 1.8V supply that powers up the displayport PLL.
-- vcca-supply: A 1.2V supply that powers up the analog circuits.
-- vcc-supply: A 1.2V supply that powers up the digital core.
-
-Optional properties:
-- interrupts-extended: Specifier for the SN65DSI86 interrupt line.
-
-- gpio-controller: Marks the device has a GPIO controller.
-- #gpio-cells    : Should be two. The first cell is the pin number and
-                   the second cell is used to specify flags.
-                   See ../../gpio/gpio.txt for more information.
-- #pwm-cells : Should be one. See ../../pwm/pwm.yaml for description of
-               the cell formats.
-
-- clock-names: should be "refclk"
-- clocks: Specification for input reference clock. The reference
-	  clock rate must be 12 MHz, 19.2 MHz, 26 MHz, 27 MHz or 38.4 MHz.
-
-- data-lanes: See ../../media/video-interface.txt
-- lane-polarities: See ../../media/video-interface.txt
-
-- suspend-gpios: specification for GPIO1 pin on bridge (active low)
-
-Required nodes:
-This device has two video ports. Their connections are modelled using the
-OF graph bindings specified in Documentation/devicetree/bindings/graph.txt.
-
-- Video port 0 for DSI input
-- Video port 1 for eDP output
-
-Example
--------
-
-edp-bridge@2d {
-	compatible = "ti,sn65dsi86";
-	#address-cells = <1>;
-	#size-cells = <0>;
-	reg = <0x2d>;
-
-	enable-gpios = <&msmgpio 33 GPIO_ACTIVE_HIGH>;
-	suspend-gpios = <&msmgpio 34 GPIO_ACTIVE_LOW>;
-
-	interrupts-extended = <&gpio3 4 IRQ_TYPE_EDGE_FALLING>;
-
-	vccio-supply = <&pm8916_l17>;
-	vcca-supply = <&pm8916_l6>;
-	vpll-supply = <&pm8916_l17>;
-	vcc-supply = <&pm8916_l6>;
-
-	clock-names = "refclk";
-	clocks = <&input_refclk>;
-
-	ports {
-		#address-cells = <1>;
-		#size-cells = <0>;
-
-		port@0 {
-			reg = <0>;
-
-			edp_bridge_in: endpoint {
-				remote-endpoint = <&dsi_out>;
-			};
-		};
-
-		port@1 {
-			reg = <1>;
-
-			edp_bridge_out: endpoint {
-				data-lanes = <2 1 3 0>;
-				lane-polarities = <0 1 0 1>;
-				remote-endpoint = <&edp_panel_in>;
-			};
-		};
-	};
-}
diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
new file mode 100644
index 000000000000..6d7d40ad45ac
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
@@ -0,0 +1,279 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/ti,sn65dsi86.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SN65DSI86 DSI to eDP bridge chip
+
+maintainers:
+  - Sandeep Panda <spanda@codeaurora.org>
+
+description: |
+  The Texas Instruments SN65DSI86 bridge takes MIPI DSI in and outputs eDP.
+  http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=sn65dsi86&fileType=pdf
+
+properties:
+  compatible:
+    const: ti,sn65dsi86
+
+  reg:
+    const: 0x2d
+
+  enable-gpios:
+    maxItems: 1
+    description: GPIO specifier for bridge_en pin (active high).
+
+  suspend-gpios:
+    maxItems: 1
+    description: GPIO specifier for GPIO1 pin on bridge (active low).
+
+  vccio-supply:
+    description: A 1.8V supply that powers the digital IOs.
+
+  vpll-supply:
+    description: A 1.8V supply that powers the DisplayPort PLL.
+
+  vcca-supply:
+    description: A 1.2V supply that powers the analog circuits.
+
+  vcc-supply:
+    description: A 1.2V supply that powers the digital core.
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+    description:
+      Clock specifier for input reference clock. The reference clock rate must
+      be 12 MHz, 19.2 MHz, 26 MHz, 27 MHz or 38.4 MHz.
+
+  clock-names:
+    const: refclk
+
+  gpio-controller: true
+  '#gpio-cells':
+    const: 2
+    description:
+      First cell is pin number, second cell is flags.  GPIO pin numbers are
+      1-based to match the datasheet.  See ../../gpio/gpio.txt for more
+      information.
+
+  '#pwm-cells':
+    const: 1
+    description: See ../../pwm/pwm.yaml for description of the cell formats.
+
+  ports:
+    type: object
+
+    properties:
+      "#address-cells":
+        const: 1
+
+      "#size-cells":
+        const: 0
+
+      port@0:
+        type: object
+        additionalProperties: false
+
+        description:
+          Video port for MIPI DSI input
+
+        properties:
+          reg:
+            const: 0
+
+          endpoint:
+            type: object
+            additionalProperties: false
+
+            properties:
+              remote-endpoint: true
+
+              data-lanes:
+                minItems: 1
+                maxItems: 4
+                items:
+                  enum:
+                    - 0
+                    - 1
+                    - 2
+                    - 3
+                description: See ../../media/video-interface.txt
+
+              lane-polarities:
+                minItems: 1
+                maxItems: 4
+                items:
+                  enum:
+                    - 0
+                    - 1
+                description: See ../../media/video-interface.txt
+
+            dependencies:
+              data-lanes: [lane-polarities]
+
+        required:
+          - reg
+
+      port@1:
+        type: object
+        additionalProperties: false
+
+        description:
+          Video port for eDP output (panel or connector).
+
+        properties:
+          reg:
+            const: 1
+
+          endpoint:
+            type: object
+            additionalProperties: false
+
+            properties:
+              remote-endpoint: true
+
+              data-lanes:
+                minItems: 1
+                maxItems: 4
+                items:
+                  enum:
+                    - 0
+                    - 1
+                    - 2
+                    - 3
+                description: See ../../media/video-interface.txt
+
+              lane-polarities:
+                minItems: 1
+                maxItems: 4
+                items:
+                  enum:
+                    - 0
+                    - 1
+                description: See ../../media/video-interface.txt
+
+            dependencies:
+              data-lanes: [lane-polarities]
+
+        required:
+          - reg
+
+    required:
+      - "#address-cells"
+      - "#size-cells"
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - reg
+  - enable-gpios
+  - vccio-supply
+  - vpll-supply
+  - vcca-supply
+  - vcc-supply
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/qcom,rpmh.h>
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      bridge@2d {
+        compatible = "ti,sn65dsi86";
+        reg = <0x2d>;
+
+        interrupt-parent = <&tlmm>;
+        interrupts = <10 IRQ_TYPE_LEVEL_HIGH>;
+
+        enable-gpios = <&tlmm 102 GPIO_ACTIVE_HIGH>;
+
+        vpll-supply = <&src_pp1800_s4a>;
+        vccio-supply = <&src_pp1800_s4a>;
+        vcca-supply = <&src_pp1200_l2a>;
+        vcc-supply = <&src_pp1200_l2a>;
+
+        clocks = <&rpmhcc RPMH_LN_BB_CLK2>;
+        clock-names = "refclk";
+
+        ports {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          port@0 {
+            reg = <0>;
+            endpoint {
+              remote-endpoint = <&dsi0_out>;
+            };
+          };
+
+          port@1 {
+            reg = <1>;
+            endpoint {
+              remote-endpoint = <&panel_in_edp>;
+            };
+          };
+        };
+      };
+    };
+  - |
+    #include <dt-bindings/clock/qcom,rpmh.h>
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      bridge@2d {
+        compatible = "ti,sn65dsi86";
+        reg = <0x2d>;
+
+        enable-gpios = <&msmgpio 33 GPIO_ACTIVE_HIGH>;
+        suspend-gpios = <&msmgpio 34 GPIO_ACTIVE_LOW>;
+
+        interrupts-extended = <&gpio3 4 IRQ_TYPE_EDGE_FALLING>;
+
+        vccio-supply = <&pm8916_l17>;
+        vcca-supply = <&pm8916_l6>;
+        vpll-supply = <&pm8916_l17>;
+        vcc-supply = <&pm8916_l6>;
+
+        clock-names = "refclk";
+        clocks = <&input_refclk>;
+
+        ports {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          port@0 {
+            reg = <0>;
+
+            edp_bridge_in: endpoint {
+              remote-endpoint = <&dsi_out>;
+            };
+          };
+
+          port@1 {
+            reg = <1>;
+
+            edp_bridge_out: endpoint {
+              data-lanes = <2 1 3 0>;
+              lane-polarities = <0 1 0 1>;
+              remote-endpoint = <&edp_panel_in>;
+            };
+          };
+        };
+      };
+    };
-- 
2.26.1.301.g55bc3eb7cb9-goog

[PATCH v3 5/6] dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd

[Douglas Anderson]

The ti-sn65dsi86 MIPI DSI to eDP bridge chip has a dedicated hardware
HPD (Hot Plug Detect) pin on it, but it's mostly useless for eDP
because of excessive debouncing in hardware.  Specifically there is no
way to disable the debouncing and for eDP debouncing hurts you because
HPD is just used for knowing when the panel is ready, not for
detecting physical plug events.

Currently the driver in Linux just assumes that nobody has HPD hooked
up.  It relies on folks setting the "no-hpd" property in the panel
node to specify that HPD isn't hooked up and then the panel driver
using this to add some worst case delays when turning on the panel.

Apparently it's also useful to specify "no-hpd" in the bridge node so
that the bridge driver can make sure it's doing the right thing
without peeking into the panel [1].  This would be used if anyone ever
found it useful to implement support for the HW HPD pin on the bridge.
Let's add this property to the bindings.

NOTES:
- This is somewhat of a backward-incompatible change.  All current
  known users of ti-sn65dsi86 didn't have "no-hpd" specified in the
  bridge node yet none of them had HPD hooked up.  This worked because
  the current Linux driver just assumed that HPD was never hooked up.
  We could make it less incompatible by saying that for this bridge
  it's assumed HPD isn't hooked up _unless_ a property is defined, but
  "no-hpd" is much more standard and it's unlikely to matter unless
  someone quickly goes and implements HPD in the driver.
- It is sensible to specify "no-hpd" at the bridge chip level and
  specify "hpd-gpios" at the panel level.  That would mean HPD is
  hooked up to some other GPIO in the system, just not the hardware
  HPD pin on the bridge chip.

[1] https://lore.kernel.org/r/20200417180819.GE5861@pendragon.ideasonboard.com

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
---

Changes in v3:
- useful implement => useful to implement

Changes in v2:
- ("dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd") new for v2.

 .../devicetree/bindings/display/bridge/ti,sn65dsi86.yaml    | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
index 6d7d40ad45ac..5746416b0f73 100644
--- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.yaml
@@ -28,6 +28,10 @@ properties:
     maxItems: 1
     description: GPIO specifier for GPIO1 pin on bridge (active low).
 
+  no-hpd:
+    type: boolean
+    description: Set if the HPD line on the bridge isn't hooked up to anything.
+
   vccio-supply:
     description: A 1.8V supply that powers the digital IOs.
 
@@ -207,6 +211,8 @@ examples:
         clocks = <&rpmhcc RPMH_LN_BB_CLK2>;
         clock-names = "refclk";
 
+        no-hpd;
+
         ports {
           #address-cells = <1>;
           #size-cells = <0>;
-- 
2.26.1.301.g55bc3eb7cb9-goog

[PATCH v3 6/6] arm64: dts: sdm845: Add "no-hpd" to sn65dsi86 on cheza

[Douglas Anderson]

We don't have the HPD line hooked up to the bridge chip.  Add it as
suggested in the patch ("dt-bindings: drm/bridge: ti-sn65dsi86:
Document no-hpd").

NOTE: this patch isn't expected to have any effect but just keeps us
cleaner for the future.  Currently the driver in Linux just assumes
that nobody has HPD hooked up.  This change allows us to later
implement HPD support in the driver without messing up sdm845-cheza.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
---

Changes in v3: None
Changes in v2:
- ("arm64: dts: sdm845: Add "no-hpd" to sn65dsi86 on cheza") new for v2.

 arch/arm64/boot/dts/qcom/sdm845-cheza.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sdm845-cheza.dtsi b/arch/arm64/boot/dts/qcom/sdm845-cheza.dtsi
index 9070be43a309..5938f8b2aa2f 100644
--- a/arch/arm64/boot/dts/qcom/sdm845-cheza.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdm845-cheza.dtsi
@@ -548,6 +548,8 @@ sn65dsi86_bridge: bridge@2d {
 		clocks = <&rpmhcc RPMH_LN_BB_CLK2>;
 		clock-names = "refclk";
 
+		no-hpd;
+
 		ports {
 			#address-cells = <1>;
 			#size-cells = <0>;
-- 
2.26.1.301.g55bc3eb7cb9-goog

Re: [PATCH v3 4/6] dt-bindings: drm/bridge: ti-sn65dsi86: Convert to yaml

[Stephen Boyd]

Quoting Douglas Anderson (2020-04-23 09:25:46)
> This moves the bindings over, based a lot on toshiba,tc358768.yaml.
> Unless there's someone known to be better, I've set the maintainer in
> the yaml as the first person to submit bindings.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Re: [PATCH v3 1/6] drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux

[Stephen Boyd]

Quoting Douglas Anderson (2020-04-23 09:25:43)
> The ti-sn65dsi86 MIPI DSI to eDP bridge chip has 4 pins on it that can
> be used as GPIOs in a system.  Each pin can be configured as input,
> output, or a special function for the bridge chip.  These are:
> - GPIO1: SUSPEND Input
> - GPIO2: DSIA VSYNC
> - GPIO3: DSIA HSYNC or VSYNC
> - GPIO4: PWM
> 
> Let's expose these pins as GPIOs.  A few notes:
> - Access to ti-sn65dsi86 is via i2c so we set "can_sleep".
> - These pins can't be configured for IRQ.
> - There are no programmable pulls or other fancy features.
> - Keeping the bridge chip powered might be expensive.  The driver is
>   setup such that if all used GPIOs are only inputs we'll power the
>   bridge chip on just long enough to read the GPIO and then power it
>   off again.  Setting a GPIO as output will keep the bridge powered.
> - If someone releases a GPIO we'll implicitly switch it to an input so
>   we no longer need to keep the bridge powered for it.
> 
> Because of all of the above limitations we just need to implement a
> bare-bones GPIO driver.  The device tree bindings already account for
> this device being a GPIO controller so we only need the driver changes
> for it.
> 
> NOTE: Despite the fact that these pins are nominally muxable I don't
> believe it makes sense to expose them through the pinctrl interface as
> well as the GPIO interface.  The special functions are things that the
> bridge chip driver itself would care about and it can just configure
> the pins as needed.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Re: [PATCH v3 2/6] dt-bindings: display: Add hpd-gpios to panel-common bindings

[Linus Walleij]

On Thu, Apr 23, 2020 at 6:26 PM Douglas Anderson <dianders@chromium.org> wrote:

> In the cases where there is no connector in a system there's no great
> place to put "hpd-gpios".  As per discussion [1] the best place to put
> it is in the panel.  Add this to the device tree bindings.
>
> [1] https://lore.kernel.org/r/20200417180819.GE5861@pendragon.ideasonboard.com
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: [PATCH v3 3/6] drm/panel-simple: Support hpd-gpios for delaying prepare()

[Linus Walleij]

On Thu, Apr 23, 2020 at 6:26 PM Douglas Anderson <dianders@chromium.org> wrote:

> People use panel-simple when they have panels that are builtin to
> their device.  In these cases the HPD (Hot Plug Detect) signal isn't
> really used for hotplugging devices but instead is used for power
> sequencing.  Panel timing diagrams (especially for eDP panels) usually
> have the HPD signal in them and it acts as an indicator that the panel
> is ready for us to talk to it.
>
> Sometimes the HPD signal is hooked up to a normal GPIO on a system.
> In this case we need to poll it in the correct place to know that the
> panel is ready for us.  In some system designs the right place for
> this is panel-simple.
>
> When adding this support, we'll account for the case that there might
> be a circular dependency between panel-simple and the provider of the
> GPIO.  The case this was designed for was for the "ti-sn65dsi86"
> bridge chip.  If HPD is hooked up to one of the GPIOs provided by the
> bridge chip then in our probe function we'll always get back
> -EPROBE_DEFER.  Let's handle this by allowing this GPIO to show up
> late if we saw -EPROBE_DEFER during probe.  NOTE: since the
> gpio_get_optional() is used, if the "hpd-gpios" isn't there our
> variable will just be NULL and we won't do anything in prepare().
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>
> ---
>
> Changes in v3:
> - Remind how gpio_get_optional() works in the commit message.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

I have a small inkling to protest against calling this driver "panel-simple"
as we tend to stockpile things like this.

I suppose panel-panacea.c is a better name at this point :/

Yours,
Linus Walleij

Re: [PATCH v3 5/6] dt-bindings: drm/bridge: ti-sn65dsi86: Document no-hpd

[Linus Walleij]

On Thu, Apr 23, 2020 at 6:26 PM Douglas Anderson <dianders@chromium.org> wrote:

> The ti-sn65dsi86 MIPI DSI to eDP bridge chip has a dedicated hardware
> HPD (Hot Plug Detect) pin on it, but it's mostly useless for eDP
> because of excessive debouncing in hardware.  Specifically there is no
> way to disable the debouncing and for eDP debouncing hurts you because
> HPD is just used for knowing when the panel is ready, not for
> detecting physical plug events.
>
> Currently the driver in Linux just assumes that nobody has HPD hooked
> up.  It relies on folks setting the "no-hpd" property in the panel
> node to specify that HPD isn't hooked up and then the panel driver
> using this to add some worst case delays when turning on the panel.
>
> Apparently it's also useful to specify "no-hpd" in the bridge node so
> that the bridge driver can make sure it's doing the right thing
> without peeking into the panel [1].  This would be used if anyone ever
> found it useful to implement support for the HW HPD pin on the bridge.
> Let's add this property to the bindings.
>
> NOTES:
> - This is somewhat of a backward-incompatible change.  All current
>   known users of ti-sn65dsi86 didn't have "no-hpd" specified in the
>   bridge node yet none of them had HPD hooked up.  This worked because
>   the current Linux driver just assumed that HPD was never hooked up.
>   We could make it less incompatible by saying that for this bridge
>   it's assumed HPD isn't hooked up _unless_ a property is defined, but
>   "no-hpd" is much more standard and it's unlikely to matter unless
>   someone quickly goes and implements HPD in the driver.
> - It is sensible to specify "no-hpd" at the bridge chip level and
>   specify "hpd-gpios" at the panel level.  That would mean HPD is
>   hooked up to some other GPIO in the system, just not the hardware
>   HPD pin on the bridge chip.
>
> [1] https://lore.kernel.org/r/20200417180819.GE5861@pendragon.ideasonboard.com
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>

Makes sense to me so:
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

> +  no-hpd:
> +    type: boolean
> +    description: Set if the HPD line on the bridge isn't hooked up to anything.

I would perhaps tag on:
... or is otherwise unusable?

Yours,
Linus Walleij

Re: [PATCH v3 1/6] drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux

[Linus Walleij]

On Thu, Apr 23, 2020 at 6:26 PM Douglas Anderson <dianders@chromium.org> wrote:

> The ti-sn65dsi86 MIPI DSI to eDP bridge chip has 4 pins on it that can
> be used as GPIOs in a system.  Each pin can be configured as input,
> output, or a special function for the bridge chip.  These are:
> - GPIO1: SUSPEND Input
> - GPIO2: DSIA VSYNC
> - GPIO3: DSIA HSYNC or VSYNC
> - GPIO4: PWM
>
> Let's expose these pins as GPIOs.  A few notes:
> - Access to ti-sn65dsi86 is via i2c so we set "can_sleep".
> - These pins can't be configured for IRQ.
> - There are no programmable pulls or other fancy features.
> - Keeping the bridge chip powered might be expensive.  The driver is
>   setup such that if all used GPIOs are only inputs we'll power the
>   bridge chip on just long enough to read the GPIO and then power it
>   off again.  Setting a GPIO as output will keep the bridge powered.
> - If someone releases a GPIO we'll implicitly switch it to an input so
>   we no longer need to keep the bridge powered for it.
>
> Because of all of the above limitations we just need to implement a
> bare-bones GPIO driver.  The device tree bindings already account for
> this device being a GPIO controller so we only need the driver changes
> for it.
>
> NOTE: Despite the fact that these pins are nominally muxable I don't
> believe it makes sense to expose them through the pinctrl interface as
> well as the GPIO interface.  The special functions are things that the
> bridge chip driver itself would care about and it can just configure
> the pins as needed.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Pretty cool.

I wonder if this chip could use the generic regmap GPIO helpers
that we are working on when they come around?
https://lore.kernel.org/linux-gpio/20200423174543.17161-11-michael@walle.cc/

> +#include <linux/gpio/driver.h>
> +#include <linux/gpio.h>

Only <linux/gpio/driver.h> should be needed else you are doing
something wrong.

> + * @gchip:        If we expose our GPIOs, this is used.
> + * @gchip_output: A cache of whether we've set GPIOs to output.  This
> + *                serves double-duty of keeping track of the direction and
> + *                also keeping track of whether we've incremented the
> + *                pm_runtime reference count for this pin, which we do
> + *                whenever a pin is configured as an output.

That sounds a bit hairy but I guess it's fine.

> + */
>  struct ti_sn_bridge {
>         struct device                   *dev;
>         struct regmap                   *regmap;
> @@ -102,6 +136,9 @@ struct ti_sn_bridge {
>         struct gpio_desc                *enable_gpio;
>         struct regulator_bulk_data      supplies[SN_REGULATOR_SUPPLY_NUM];
>         int                             dp_lanes;
> +
> +       struct gpio_chip                gchip;
> +       DECLARE_BITMAP(gchip_output, SN_NUM_GPIOS);

Do you really need a bitmap for 4 bits? Can't you just have something
like an u8 and check bit 0,1,2,3 ... well I suppose it has some elegance to
it as well but... hm.

> +static struct ti_sn_bridge *gchip_to_pdata(struct gpio_chip *chip)
> +{
> +       return container_of(chip, struct ti_sn_bridge, gchip);
> +}
> +
> +static int ti_sn_bridge_gpio_get_direction(struct gpio_chip *chip,
> +                                          unsigned int offset)
> +{
> +       struct ti_sn_bridge *pdata = gchip_to_pdata(chip);

Is there some specific reason why you don't just use
gpiochip_get_data()?

> +       /*
> +        * We already have to keep track of the direction because we use
> +        * that to figure out whether we've powered the device.  We can
> +        * just return that rather than (maybe) powering up the device
> +        * to ask its direction.
> +        */
> +       return test_bit(offset, pdata->gchip_output) ?
> +               GPIOF_DIR_OUT : GPIOF_DIR_IN;
> +}

Don't use these legacy defines, they are for consumers.
Use GPIO_LINE_DIRECTION_IN  and GPIO_LINE_DIRECTION_OUT.
from <linux/gpio/driver.h>

> +       ret = regmap_read(pdata->regmap, SN_GPIO_IO_REG, &val);
> +       pm_runtime_put(pdata->dev);
> +
> +       if (ret)
> +               return ret;
> +
> +       return (val >> (SN_GPIO_INPUT_SHIFT + offset)) & 1;

My preferred way to do this is:

#include <linux/bits.h>

return !!(val & BIT(SN_GPIO_INPUT_SHIFT + offset));

> +static void ti_sn_bridge_gpio_set(struct gpio_chip *chip, unsigned int offset,
> +                                 int val)
> +{
> +       struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
> +       int ret;
> +
> +       if (!test_bit(offset, pdata->gchip_output)) {
> +               dev_err(pdata->dev, "Ignoring GPIO set while input\n");
> +               return;
> +       }
> +
> +       val &= 1;
> +       ret = regmap_update_bits(pdata->regmap, SN_GPIO_IO_REG,
> +                                BIT(SN_GPIO_OUTPUT_SHIFT + offset),
> +                                val << (SN_GPIO_OUTPUT_SHIFT + offset));

Looks like a job for the generic helper library.

> +static int ti_sn_bridge_gpio_direction_input(struct gpio_chip *chip,
> +                                            unsigned int offset)
> +{
> +       struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
> +       int shift = offset * 2;
> +       int ret;
> +
> +       if (!test_and_clear_bit(offset, pdata->gchip_output))
> +               return 0;
> +
> +       ret = regmap_update_bits(pdata->regmap, SN_GPIO_CTRL_REG,
> +                                0x3 << shift, SN_GPIO_MUX_INPUT << shift);

But this 0x03 does not look very generic, it's not just 1 bit but 2.

Overall it looks good, just the minor things above need fixing or
looking into.

Yours,
Linus Walleij

Re: [PATCH v3 1/6] drm/bridge: ti-sn65dsi86: Export bridge GPIOs to Linux

[Doug Anderson]

Hi,

On Tue, Apr 28, 2020 at 5:44 AM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Thu, Apr 23, 2020 at 6:26 PM Douglas Anderson <dianders@chromium.org> wrote:
>
> > The ti-sn65dsi86 MIPI DSI to eDP bridge chip has 4 pins on it that can
> > be used as GPIOs in a system.  Each pin can be configured as input,
> > output, or a special function for the bridge chip.  These are:
> > - GPIO1: SUSPEND Input
> > - GPIO2: DSIA VSYNC
> > - GPIO3: DSIA HSYNC or VSYNC
> > - GPIO4: PWM
> >
> > Let's expose these pins as GPIOs.  A few notes:
> > - Access to ti-sn65dsi86 is via i2c so we set "can_sleep".
> > - These pins can't be configured for IRQ.
> > - There are no programmable pulls or other fancy features.
> > - Keeping the bridge chip powered might be expensive.  The driver is
> >   setup such that if all used GPIOs are only inputs we'll power the
> >   bridge chip on just long enough to read the GPIO and then power it
> >   off again.  Setting a GPIO as output will keep the bridge powered.
> > - If someone releases a GPIO we'll implicitly switch it to an input so
> >   we no longer need to keep the bridge powered for it.
> >
> > Because of all of the above limitations we just need to implement a
> > bare-bones GPIO driver.  The device tree bindings already account for
> > this device being a GPIO controller so we only need the driver changes
> > for it.
> >
> > NOTE: Despite the fact that these pins are nominally muxable I don't
> > believe it makes sense to expose them through the pinctrl interface as
> > well as the GPIO interface.  The special functions are things that the
> > bridge chip driver itself would care about and it can just configure
> > the pins as needed.
> >
> > Signed-off-by: Douglas Anderson <dianders@chromium.org>
> > Cc: Linus Walleij <linus.walleij@linaro.org>
> > Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> Pretty cool.
>
> I wonder if this chip could use the generic regmap GPIO helpers
> that we are working on when they come around?
> https://lore.kernel.org/linux-gpio/20200423174543.17161-11-michael@walle.cc/

An important part of my patch is the handling of power management.
Specifically:
* If the GPIO is an input we don't need to keep the device powered,
just power it temporarily to read the pin.
* If the GPIO is an output we do need to keep the device powered.

I suppose that could be common for other similar devices so as long as
the generic interfaces can handle this concept we can try to use it.


> > +#include <linux/gpio/driver.h>
> > +#include <linux/gpio.h>
>
> Only <linux/gpio/driver.h> should be needed else you are doing
> something wrong.

It's because I needed GPIOF_DIR_OUT / GPIOF_DIR_IN which was
apparently wrong.  See below.


> > + * @gchip:        If we expose our GPIOs, this is used.
> > + * @gchip_output: A cache of whether we've set GPIOs to output.  This
> > + *                serves double-duty of keeping track of the direction and
> > + *                also keeping track of whether we've incremented the
> > + *                pm_runtime reference count for this pin, which we do
> > + *                whenever a pin is configured as an output.
>
> That sounds a bit hairy but I guess it's fine.
>
> > + */
> >  struct ti_sn_bridge {
> >         struct device                   *dev;
> >         struct regmap                   *regmap;
> > @@ -102,6 +136,9 @@ struct ti_sn_bridge {
> >         struct gpio_desc                *enable_gpio;
> >         struct regulator_bulk_data      supplies[SN_REGULATOR_SUPPLY_NUM];
> >         int                             dp_lanes;
> > +
> > +       struct gpio_chip                gchip;
> > +       DECLARE_BITMAP(gchip_output, SN_NUM_GPIOS);
>
> Do you really need a bitmap for 4 bits? Can't you just have something
> like an u8 and check bit 0,1,2,3 ... well I suppose it has some elegance to
> it as well but... hm.

Doing so requires adding a lock to this driver to handle concurrent
users of the different GPIOs.  I can go back and do that but I'd
rather not.

Some prior discussion:

https://lore.kernel.org/r/CAD=FV=WJONhm4ukwZa2vGtozrz_SmLuTCLxVimnGba7wRPPzgQ@mail.gmail.com

...if you want me to change this to a u8 + a mutex then please let me
know, otherwise I'll assume keeping it a bitmap is fine.


> > +static struct ti_sn_bridge *gchip_to_pdata(struct gpio_chip *chip)
> > +{
> > +       return container_of(chip, struct ti_sn_bridge, gchip);
> > +}
> > +
> > +static int ti_sn_bridge_gpio_get_direction(struct gpio_chip *chip,
> > +                                          unsigned int offset)
> > +{
> > +       struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
>
> Is there some specific reason why you don't just use
> gpiochip_get_data()?

I guess I'm used to interfaces that don't have a data pointer.  I'll
change it to gpiochip_get_data() at your suggestion, though (I think)
it might be slightly less efficient (a function call and a pointer
dereference compared to a subtract operation).


> > +       /*
> > +        * We already have to keep track of the direction because we use
> > +        * that to figure out whether we've powered the device.  We can
> > +        * just return that rather than (maybe) powering up the device
> > +        * to ask its direction.
> > +        */
> > +       return test_bit(offset, pdata->gchip_output) ?
> > +               GPIOF_DIR_OUT : GPIOF_DIR_IN;
> > +}
>
> Don't use these legacy defines, they are for consumers.
> Use GPIO_LINE_DIRECTION_IN  and GPIO_LINE_DIRECTION_OUT.
> from <linux/gpio/driver.h>

That's what I get for reading the comments.  I'll change this in the
next version.  I've also sent the following patch to help keep other
people from falling into my trap:

https://lore.kernel.org/r/20200428172322.1.I396f351e364f3c09df7c7606e79abefb8682c092@changeid/


> > +       ret = regmap_read(pdata->regmap, SN_GPIO_IO_REG, &val);
> > +       pm_runtime_put(pdata->dev);
> > +
> > +       if (ret)
> > +               return ret;
> > +
> > +       return (val >> (SN_GPIO_INPUT_SHIFT + offset)) & 1;
>
> My preferred way to do this is:
>
> #include <linux/bits.h>
>
> return !!(val & BIT(SN_GPIO_INPUT_SHIFT + offset));

Somehow I think of "!!" as being a bool and this function as returning
something that's logically an int.  It really doesn't matter a whole
lot and I'm happy to change it, so I'll change it in the next version.


> > +static void ti_sn_bridge_gpio_set(struct gpio_chip *chip, unsigned int offset,
> > +                                 int val)
> > +{
> > +       struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
> > +       int ret;
> > +
> > +       if (!test_bit(offset, pdata->gchip_output)) {
> > +               dev_err(pdata->dev, "Ignoring GPIO set while input\n");
> > +               return;
> > +       }
> > +
> > +       val &= 1;
> > +       ret = regmap_update_bits(pdata->regmap, SN_GPIO_IO_REG,
> > +                                BIT(SN_GPIO_OUTPUT_SHIFT + offset),
> > +                                val << (SN_GPIO_OUTPUT_SHIFT + offset));
>
> Looks like a job for the generic helper library.

I think that (for now) this comment is a no-op since the generic
helper library isn't landed yet, right?  ...and it wouldn't handle the
power management I need?  If I'm confused and I need to act on this
comment, please let me know.


> > +static int ti_sn_bridge_gpio_direction_input(struct gpio_chip *chip,
> > +                                            unsigned int offset)
> > +{
> > +       struct ti_sn_bridge *pdata = gchip_to_pdata(chip);
> > +       int shift = offset * 2;
> > +       int ret;
> > +
> > +       if (!test_and_clear_bit(offset, pdata->gchip_output))
> > +               return 0;
> > +
> > +       ret = regmap_update_bits(pdata->regmap, SN_GPIO_CTRL_REG,
> > +                                0x3 << shift, SN_GPIO_MUX_INPUT << shift);
>
> But this 0x03 does not look very generic, it's not just 1 bit but 2.

Sure, I can add #define SN_GPIO_MUX_MASK 0x3.  Basically the mux is:

* 0: input
* 1: output
* 2: special function

As talked about in the patch comments, I don't define this as an
official pinmux driver because that seems overkill.  I'll assume it's
OK to just do the #define and use it.  If you want something more, let
me know.


> Overall it looks good, just the minor things above need fixing or
> looking into.

Thank you very much for the review!  I'll plan to send a new patch out
in the next day or two with minor comments addressed and making the
assumptions I've documented above.  If I got something wrong then
please yell.  ...or yell after I send the next version and I'll send
yet another version after that!  :-)

-Doug