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-rw-r--r--board/chromebook/elm/patches/linux/0005-drm-bridge-ps8640-Rework-power-state-handling.patch162
1 files changed, 162 insertions, 0 deletions
diff --git a/board/chromebook/elm/patches/linux/0005-drm-bridge-ps8640-Rework-power-state-handling.patch b/board/chromebook/elm/patches/linux/0005-drm-bridge-ps8640-Rework-power-state-handling.patch
new file mode 100644
index 0000000000..f682600d11
--- /dev/null
+++ b/board/chromebook/elm/patches/linux/0005-drm-bridge-ps8640-Rework-power-state-handling.patch
@@ -0,0 +1,162 @@
+From 5bb60fe7c748a0aae2bdbab10e73b2dc48c09dda Mon Sep 17 00:00:00 2001
+From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+Date: Wed, 26 Aug 2020 10:15:26 +0200
+Subject: [PATCH 5/5] drm/bridge: ps8640: Rework power state handling
+
+The get_edid() callback can be triggered anytime by an ioctl, i.e
+
+ drm_mode_getconnector (ioctl)
+ -> drm_helper_probe_single_connector_modes
+ -> drm_bridge_connector_get_modes
+ -> ps8640_bridge_get_edid
+
+Actually if the bridge pre_enable() function was not called before
+get_edid(), the driver will not be able to get the EDID properly and
+display will not work until a second get_edid() call is issued and if
+pre_enable() is called before. The side effect of this, for example, is
+that you see anything when `Frecon` starts, neither the splash screen,
+until the graphical session manager starts.
+
+To fix this we need to make sure that all we need is enabled before
+reading the EDID. This means the following:
+
+1. If get_edid() is called before having the device powered we need to
+ power on the device. In such case, the driver will power off again the
+ device.
+
+2. If get_edid() is called after having the device powered, all should
+ just work. We added a powered flag in order to avoid recurrent calls
+ to ps8640_bridge_poweron() and unneeded delays.
+
+3. This seems to be specific for this device, but we need to make sure
+ the panel is powered on before do a power on cycle on this device.
+ Otherwise the device fails to retrieve the EDID.
+
+Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
+---
+ drivers/gpu/drm/bridge/parade-ps8640.c | 64 +++++++++++++++++++++++---
+ 1 file changed, 58 insertions(+), 6 deletions(-)
+
+diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
+index 9f7b7a9c53c5..c5d76e209bda 100644
+--- a/drivers/gpu/drm/bridge/parade-ps8640.c
++++ b/drivers/gpu/drm/bridge/parade-ps8640.c
+@@ -65,6 +65,7 @@ struct ps8640 {
+ struct regulator_bulk_data supplies[2];
+ struct gpio_desc *gpio_reset;
+ struct gpio_desc *gpio_powerdown;
++ bool powered;
+ };
+
+ static inline struct ps8640 *bridge_to_ps8640(struct drm_bridge *e)
+@@ -91,13 +92,15 @@ static int ps8640_bridge_vdo_control(struct ps8640 *ps_bridge,
+ return 0;
+ }
+
+-static void ps8640_pre_enable(struct drm_bridge *bridge)
++static void ps8640_bridge_poweron(struct ps8640 *ps_bridge)
+ {
+- struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+ struct i2c_client *client = ps_bridge->page[PAGE2_TOP_CNTL];
+ unsigned long timeout;
+ int ret, status;
+
++ if (ps_bridge->powered)
++ return;
++
+ ret = regulator_bulk_enable(ARRAY_SIZE(ps_bridge->supplies),
+ ps_bridge->supplies);
+ if (ret < 0) {
+@@ -164,6 +167,8 @@ static void ps8640_pre_enable(struct drm_bridge *bridge)
+ goto err_regulators_disable;
+ }
+
++ ps_bridge->powered = true;
++
+ return;
+
+ err_regulators_disable:
+@@ -171,12 +176,12 @@ static void ps8640_pre_enable(struct drm_bridge *bridge)
+ ps_bridge->supplies);
+ }
+
+-static void ps8640_post_disable(struct drm_bridge *bridge)
++static void ps8640_bridge_poweroff(struct ps8640 *ps_bridge)
+ {
+- struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+ int ret;
+
+- ps8640_bridge_vdo_control(ps_bridge, DISABLE);
++ if (!ps_bridge->powered)
++ return;
+
+ gpiod_set_value(ps_bridge->gpio_reset, 1);
+ gpiod_set_value(ps_bridge->gpio_powerdown, 1);
+@@ -184,6 +189,28 @@ static void ps8640_post_disable(struct drm_bridge *bridge)
+ ps_bridge->supplies);
+ if (ret < 0)
+ DRM_ERROR("cannot disable regulators %d\n", ret);
++
++ ps_bridge->powered = false;
++}
++
++static void ps8640_pre_enable(struct drm_bridge *bridge)
++{
++ struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
++ int ret;
++
++ ps8640_bridge_poweron(ps_bridge);
++
++ ret = ps8640_bridge_vdo_control(ps_bridge, DISABLE);
++ if (ret < 0)
++ ps8640_bridge_poweroff(ps_bridge);
++}
++
++static void ps8640_post_disable(struct drm_bridge *bridge)
++{
++ struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
++
++ ps8640_bridge_vdo_control(ps_bridge, DISABLE);
++ ps8640_bridge_poweroff(ps_bridge);
+ }
+
+ static int ps8640_bridge_attach(struct drm_bridge *bridge,
+@@ -249,9 +276,34 @@ 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;
++ struct edid *edid;
++
++ /*
++ * When we end calling get_edid() triggered by an ioctl, i.e
++ *
++ * drm_mode_getconnector (ioctl)
++ * -> drm_helper_probe_single_connector_modes
++ * -> drm_bridge_connector_get_modes
++ * -> ps8640_bridge_get_edid
++ *
++ * We need to make sure that what we need is enabled before reading
++ * EDID, for this chip, we need to do a full poweron, otherwise it will
++ * fail.
++ */
++ drm_bridge_chain_pre_enable(bridge);
+
+- return drm_get_edid(connector,
++ edid = drm_get_edid(connector,
+ ps_bridge->page[PAGE0_DP_CNTL]->adapter);
++
++ /*
++ * If we call the get_edid() function without having enabled the chip
++ * before, return the chip to its original power state.
++ */
++ if (poweroff)
++ drm_bridge_chain_post_disable(bridge);
++
++ return edid;
+ }
+
+ static const struct drm_bridge_funcs ps8640_bridge_funcs = {
+--
+2.25.1
+