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From:   Philip Chen <philipchen@chromium.org>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     swboyd@chromium.org, dianders@chromium.org,
        Philip Chen <philipchen@chromium.org>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Robert Foss <robert.foss@linaro.org>,
        dri-devel@lists.freedesktop.org
Subject: [PATCH v5 1/2] drm/bridge: parade-ps8640: Enable runtime power management
Date:   Thu, 28 Oct 2021 10:58:10 -0700
Message-Id: <20211028105754.v5.1.I828f5db745535fb7e36e8ffdd62d546f6d08b6d1@changeid>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Fit ps8640 driver into runtime power management framework:

First, break _poweron() to 3 parts: (1) turn on power and wait for
ps8640's internal MCU to finish init (2) check panel HPD (which is
proxied by GPIO9) (3) the other configs. As runtime_resume() can be
called before panel is powered, we only add (1) to _resume() and leave
(2)(3) to _pre_enable(). We also add (2) to _aux_transfer() as we want
to ensure panel HPD is asserted before we start AUX CH transactions.

Second, the original driver has a mysterious delay of 50 ms between (2)
and (3). Since Parade's support can't explain what the delay is for,
and we don't see removing the delay break any boards at hand, remove
the delay to fit into this driver change.

In addition, rename "powered" to "pre_enabled" and don't check for it
in the pm_runtime calls. The pm_runtime calls are already refcounted
so there's no reason to check there. The other user of "powered",
_get_edid(), only cares if pre_enable() has already been called.

Lastly, change some existing DRM_...() logging to dev_...() along the
way, since DRM_...() seem to be deprecated in [1].

[1] https://patchwork.freedesktop.org/patch/454760/

Signed-off-by: Philip Chen <philipchen@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
---
In v3, I added pm_suspend_ignore_children() in ps8640_probe().
Also, I moved the change of "put_sync_suspend" from patch 2/2 to here.
But I forgot to mention both changes. So edit v3 change log retroactively.

In v4, I moved the change of "ps8640_ensure_hpd" return data type
from patch 2/2 to here. But I forgot to mention it. So edit v4 change log
retroactively.

Changes in v5:
- Move the implementation of _runtime_disable() around to resolve merge
  conflict when rebasing.
- Improve the document for how autosuspend_delay is picked.

Changes in v4:
- Make ps8640_ensure_hpd() return int (This change was mis-added to
  patch 2/2 in this patch series).

Changes in v3:
- Fix typo/wording in the commit message.
- Add ps8640_aux_transfer_msg() for AUX operation. In
  ps8640_aux_transfer(), wrap around ps8640_aux_transfer_msg()
  with PM operations and HPD check.
- Document why autosuspend_delay is set to 500ms.
- Add pm_suspend_ignore_children() in ps8640_probe()
- Replace _put_sync() with _put_sync_suspend() in ps8640_post_disable()
  (The change was mis-added to patch 2/2 in this patch series.)

 drivers/gpu/drm/bridge/parade-ps8640.c | 190 ++++++++++++++++---------
 1 file changed, 119 insertions(+), 71 deletions(-)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index 4b36e4dc78f1..63a817d92c1d 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -9,6 +9,7 @@
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/of_graph.h>
+#include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 
@@ -100,7 +101,7 @@ struct ps8640 {
 	struct regulator_bulk_data supplies[2];
 	struct gpio_desc *gpio_reset;
 	struct gpio_desc *gpio_powerdown;
-	bool powered;
+	bool pre_enabled;
 };
 
 static const struct regmap_config ps8640_regmap_config[] = {
@@ -148,8 +149,29 @@ static inline struct ps8640 *aux_to_ps8640(struct drm_dp_aux *aux)
 	return container_of(aux, struct ps8640, aux);
 }
 
-static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
-				   struct drm_dp_aux_msg *msg)
+static int ps8640_ensure_hpd(struct ps8640 *ps_bridge)
+{
+	struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL];
+	struct device *dev = &ps_bridge->page[PAGE2_TOP_CNTL]->dev;
+	int status;
+	int ret;
+
+	/*
+	 * Apparently something about the firmware in the chip signals that
+	 * HPD goes high by reporting GPIO9 as high (even though HPD isn't
+	 * actually connected to GPIO9).
+	 */
+	ret = regmap_read_poll_timeout(map, PAGE2_GPIO_H, status,
+				status & PS_GPIO9, 20 * 1000, 200 * 1000);
+
+	if (ret < 0)
+		dev_warn(dev, "HPD didn't go high: %d\n", ret);
+
+	return ret;
+}
+
+static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux,
+				       struct drm_dp_aux_msg *msg)
 {
 	struct ps8640 *ps_bridge = aux_to_ps8640(aux);
 	struct regmap *map = ps_bridge->regmap[PAGE0_DP_CNTL];
@@ -274,38 +296,49 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
 	return len;
 }
 
-static int ps8640_bridge_vdo_control(struct ps8640 *ps_bridge,
-				     const enum ps8640_vdo_control ctrl)
+static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
+				   struct drm_dp_aux_msg *msg)
+{
+	struct ps8640 *ps_bridge = aux_to_ps8640(aux);
+	struct device *dev = &ps_bridge->page[PAGE0_DP_CNTL]->dev;
+	int ret;
+
+	pm_runtime_get_sync(dev);
+	ret = ps8640_ensure_hpd(ps_bridge);
+	if (!ret)
+		ret = ps8640_aux_transfer_msg(aux, msg);
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	return ret;
+}
+
+static void ps8640_bridge_vdo_control(struct ps8640 *ps_bridge,
+				      const enum ps8640_vdo_control ctrl)
 {
 	struct regmap *map = ps_bridge->regmap[PAGE3_DSI_CNTL1];
+	struct device *dev = &ps_bridge->page[PAGE3_DSI_CNTL1]->dev;
 	u8 vdo_ctrl_buf[] = { VDO_CTL_ADD, ctrl };
 	int ret;
 
 	ret = regmap_bulk_write(map, PAGE3_SET_ADD,
 				vdo_ctrl_buf, sizeof(vdo_ctrl_buf));
 
-	if (ret < 0) {
-		DRM_ERROR("failed to %sable VDO: %d\n",
-			  ctrl == ENABLE ? "en" : "dis", ret);
-		return ret;
-	}
-
-	return 0;
+	if (ret < 0)
+		dev_err(dev, "failed to %sable VDO: %d\n",
+			ctrl == ENABLE ? "en" : "dis", ret);
 }
 
-static void ps8640_bridge_poweron(struct ps8640 *ps_bridge)
+static int __maybe_unused ps8640_resume(struct device *dev)
 {
-	struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL];
-	int ret, status;
-
-	if (ps_bridge->powered)
-		return;
+	struct ps8640 *ps_bridge = dev_get_drvdata(dev);
+	int ret;
 
 	ret = regulator_bulk_enable(ARRAY_SIZE(ps_bridge->supplies),
 				    ps_bridge->supplies);
 	if (ret < 0) {
-		DRM_ERROR("cannot enable regulators %d\n", ret);
-		return;
+		dev_err(dev, "cannot enable regulators %d\n", ret);
+		return ret;
 	}
 
 	gpiod_set_value(ps_bridge->gpio_powerdown, 0);
@@ -314,86 +347,78 @@ static void ps8640_bridge_poweron(struct ps8640 *ps_bridge)
 	gpiod_set_value(ps_bridge->gpio_reset, 0);
 
 	/*
-	 * Wait for the ps8640 embedded MCU to be ready
-	 * First wait 200ms and then check the MCU ready flag every 20ms
+	 * Mystery 200 ms delay for the "MCU to be ready". It's unclear if
+	 * this is truly necessary since the MCU will already signal that
+	 * things are "good to go" by signaling HPD on "gpio 9". See
+	 * ps8640_ensure_hpd(). For now we'll keep this mystery delay just in
+	 * case.
 	 */
 	msleep(200);
 
-	ret = regmap_read_poll_timeout(map, PAGE2_GPIO_H, status,
-				       status & PS_GPIO9, 20 * 1000, 200 * 1000);
-
-	if (ret < 0) {
-		DRM_ERROR("failed read PAGE2_GPIO_H: %d\n", ret);
-		goto err_regulators_disable;
-	}
-
-	msleep(50);
-
-	/*
-	 * The Manufacturer Command Set (MCS) is a device dependent interface
-	 * intended for factory programming of the display module default
-	 * parameters. Once the display module is configured, the MCS shall be
-	 * disabled by the manufacturer. Once disabled, all MCS commands are
-	 * ignored by the display interface.
-	 */
-
-	ret = regmap_update_bits(map, PAGE2_MCS_EN, MCS_EN, 0);
-	if (ret < 0) {
-		DRM_ERROR("failed write PAGE2_MCS_EN: %d\n", ret);
-		goto err_regulators_disable;
-	}
-
-	/* Switch access edp panel's edid through i2c */
-	ret = regmap_write(map, PAGE2_I2C_BYPASS, I2C_BYPASS_EN);
-	if (ret < 0) {
-		DRM_ERROR("failed write PAGE2_I2C_BYPASS: %d\n", ret);
-		goto err_regulators_disable;
-	}
-
-	ps_bridge->powered = true;
-
-	return;
-
-err_regulators_disable:
-	regulator_bulk_disable(ARRAY_SIZE(ps_bridge->supplies),
-			       ps_bridge->supplies);
+	return 0;
 }
 
-static void ps8640_bridge_poweroff(struct ps8640 *ps_bridge)
+static int __maybe_unused ps8640_suspend(struct device *dev)
 {
+	struct ps8640 *ps_bridge = dev_get_drvdata(dev);
 	int ret;
 
-	if (!ps_bridge->powered)
-		return;
-
 	gpiod_set_value(ps_bridge->gpio_reset, 1);
 	gpiod_set_value(ps_bridge->gpio_powerdown, 1);
 	ret = regulator_bulk_disable(ARRAY_SIZE(ps_bridge->supplies),
 				     ps_bridge->supplies);
 	if (ret < 0)
-		DRM_ERROR("cannot disable regulators %d\n", ret);
+		dev_err(dev, "cannot disable regulators %d\n", ret);
 
-	ps_bridge->powered = false;
+	return ret;
 }
 
+static const struct dev_pm_ops ps8640_pm_ops = {
+	SET_RUNTIME_PM_OPS(ps8640_suspend, ps8640_resume, NULL)
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+};
+
 static void ps8640_pre_enable(struct drm_bridge *bridge)
 {
 	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+	struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL];
+	struct device *dev = &ps_bridge->page[PAGE0_DP_CNTL]->dev;
 	int ret;
 
-	ps8640_bridge_poweron(ps_bridge);
+	pm_runtime_get_sync(dev);
+	ps8640_ensure_hpd(ps_bridge);
+
+	/*
+	 * The Manufacturer Command Set (MCS) is a device dependent interface
+	 * intended for factory programming of the display module default
+	 * parameters. Once the display module is configured, the MCS shall be
+	 * disabled by the manufacturer. Once disabled, all MCS commands are
+	 * ignored by the display interface.
+	 */
+
+	ret = regmap_update_bits(map, PAGE2_MCS_EN, MCS_EN, 0);
+	if (ret < 0)
+		dev_warn(dev, "failed write PAGE2_MCS_EN: %d\n", ret);
 
-	ret = ps8640_bridge_vdo_control(ps_bridge, ENABLE);
+	/* Switch access edp panel's edid through i2c */
+	ret = regmap_write(map, PAGE2_I2C_BYPASS, I2C_BYPASS_EN);
 	if (ret < 0)
-		ps8640_bridge_poweroff(ps_bridge);
+		dev_warn(dev, "failed write PAGE2_MCS_EN: %d\n", ret);
+
+	ps8640_bridge_vdo_control(ps_bridge, ENABLE);
+
+	ps_bridge->pre_enabled = true;
 }
 
 static void ps8640_post_disable(struct drm_bridge *bridge)
 {
 	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
 
+	ps_bridge->pre_enabled = false;
+
 	ps8640_bridge_vdo_control(ps_bridge, DISABLE);
-	ps8640_bridge_poweroff(ps_bridge);
+	pm_runtime_put_sync_suspend(&ps_bridge->page[PAGE0_DP_CNTL]->dev);
 }
 
 static int ps8640_bridge_attach(struct drm_bridge *bridge,
@@ -426,7 +451,7 @@ static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
 					   struct drm_connector *connector)
 {
 	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
-	bool poweroff = !ps_bridge->powered;
+	bool poweroff = !ps_bridge->pre_enabled;
 	struct edid *edid;
 
 	/*
@@ -456,6 +481,12 @@ static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
 	return edid;
 }
 
+static void ps8640_runtime_disable(void *data)
+{
+	pm_runtime_dont_use_autosuspend(data);
+	pm_runtime_disable(data);
+}
+
 static const struct drm_bridge_funcs ps8640_bridge_funcs = {
 	.attach = ps8640_bridge_attach,
 	.detach = ps8640_bridge_detach,
@@ -586,6 +617,22 @@ static int ps8640_probe(struct i2c_client *client)
 	ps_bridge->aux.transfer = ps8640_aux_transfer;
 	drm_dp_aux_init(&ps_bridge->aux);
 
+	pm_runtime_enable(dev);
+	/*
+	 * Powering on ps8640 takes ~300ms. To avoid wasting time on power
+	 * cycling ps8640 too often, set autosuspend_delay to 500ms to ensure
+	 * the bridge wouldn't suspend in between each _aux_transfer_msg() call
+	 * during EDID read (~20ms in my experiment) and in between the last
+	 * _aux_transfer_msg() call during EDID read and the _pre_enable() call
+	 * (~100ms in my experiment).
+	 */
+	pm_runtime_set_autosuspend_delay(dev, 500);
+	pm_runtime_use_autosuspend(dev);
+	pm_suspend_ignore_children(dev, true);
+	ret = devm_add_action_or_reset(dev, ps8640_runtime_disable, dev);
+	if (ret)
+		return ret;
+
 	drm_bridge_add(&ps_bridge->bridge);
 
 	ret = ps8640_bridge_host_attach(dev, ps_bridge);
@@ -620,6 +667,7 @@ static struct i2c_driver ps8640_driver = {
 	.driver = {
 		.name = "ps8640",
 		.of_match_table = ps8640_match,
+		.pm = &ps8640_pm_ops,
 	},
 };
 module_i2c_driver(ps8640_driver);
-- 
2.33.0.1079.g6e70778dc9-goog