[PATCH v2 0/5] drm/bridge: ps8640: Make sure all needed is powered to get the EDID

[PATCH v2 0/5] drm/bridge: ps8640: Make sure all needed is powered to get the EDID

[Enric Balletbo i Serra]

The first patch was initially part of the series [1] but for some reason
was not picked when the series were merged, so I included in this series
because it is needed to make the others to work properly.

The same happened for the second patch, was part of series [1] but not
merged.

The third patch and next are part of the original series and are to rework
the power handling to get the EDID. Basically, we need to make sure all the
needed is powered to be able to get the EDID. Before, we saw that getting
the EDID failed as explained in the third patch.

[1] https://lkml.org/lkml/2020/6/15/1208

Changes in v2:
- Included the patch `drm/bridge_connector: Set default status connected for eDP connectors`
- Included the patch `drm/bridge: ps8640: Get the EDID from eDP control`
- Use drm_bridge_chain_pre_enable/post_disable() helpers (Sam Ravnborg)

Enric Balletbo i Serra (5):
  drm/bridge_connector: Set default status connected for eDP connectors
  drm/bridge: ps8640: Get the EDID from eDP control
  drm/bridge: ps8640: Return an error for incorrect attach flags
  drm/bridge: ps8640: Print an error if VDO control fails
  drm/bridge: ps8640: Rework power state handling

 drivers/gpu/drm/bridge/parade-ps8640.c | 89 ++++++++++++++++++++++----
 drivers/gpu/drm/drm_bridge_connector.c |  1 +
 2 files changed, 79 insertions(+), 11 deletions(-)

-- 
2.28.0

[PATCH v2 1/5] drm/bridge_connector: Set default status connected for eDP connectors

[Enric Balletbo i Serra]

In an eDP application, HPD is not required and on most bridge chips
useless. If HPD is not used, we need to set initial status as connected,
otherwise the connector created by the drm_bridge_connector API remains
in an unknown state.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---

Changes in v2:
- Included the patch `drm/bridge_connector: Set default status connected for eDP connectors`

 drivers/gpu/drm/drm_bridge_connector.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/drm_bridge_connector.c b/drivers/gpu/drm/drm_bridge_connector.c
index c6994fe673f3..a58cbde59c34 100644
--- a/drivers/gpu/drm/drm_bridge_connector.c
+++ b/drivers/gpu/drm/drm_bridge_connector.c
@@ -187,6 +187,7 @@ drm_bridge_connector_detect(struct drm_connector *connector, bool force)
 		case DRM_MODE_CONNECTOR_DPI:
 		case DRM_MODE_CONNECTOR_LVDS:
 		case DRM_MODE_CONNECTOR_DSI:
+		case DRM_MODE_CONNECTOR_eDP:
 			status = connector_status_connected;
 			break;
 		default:
-- 
2.28.0

[PATCH v2 2/5] drm/bridge: ps8640: Get the EDID from eDP control

[Enric Balletbo i Serra]

The PS8640 DSI-to-eDP bridge can retrieve the EDID, so implement the
.get_edid callback and set the flag to indicate the core to use it.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---

Changes in v2:
- Included the patch `drm/bridge: ps8640: Get the EDID from eDP control`

 drivers/gpu/drm/bridge/parade-ps8640.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index 4b099196afeb..13755d278db6 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -242,8 +242,18 @@ static int ps8640_bridge_attach(struct drm_bridge *bridge,
 	return ret;
 }
 
+static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
+					   struct drm_connector *connector)
+{
+	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
+
+	return drm_get_edid(connector,
+			    ps_bridge->page[PAGE0_DP_CNTL]->adapter);
+}
+
 static const struct drm_bridge_funcs ps8640_bridge_funcs = {
 	.attach = ps8640_bridge_attach,
+	.get_edid = ps8640_bridge_get_edid,
 	.post_disable = ps8640_post_disable,
 	.pre_enable = ps8640_pre_enable,
 };
@@ -294,6 +304,8 @@ static int ps8640_probe(struct i2c_client *client)
 
 	ps_bridge->bridge.funcs = &ps8640_bridge_funcs;
 	ps_bridge->bridge.of_node = dev->of_node;
+	ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID;
+	ps_bridge->bridge.type = DRM_MODE_CONNECTOR_eDP;
 
 	ps_bridge->page[PAGE0_DP_CNTL] = client;
 
-- 
2.28.0

[PATCH v2 3/5] drm/bridge: ps8640: Return an error for incorrect attach flags

[Enric Balletbo i Serra]

Bridge drivers that implement the new model only shall return an error
from their attach() handler when the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag
is not set. So make sure we return an error because only the new
drm_bridge model is supported.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---

Changes in v2: None

 drivers/gpu/drm/bridge/parade-ps8640.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index 13755d278db6..ce3e8b2da8c9 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -200,6 +200,10 @@ static int ps8640_bridge_attach(struct drm_bridge *bridge,
 						   .channel = 0,
 						   .node = NULL,
 						 };
+
+	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
+		return -EINVAL;
+
 	/* port@0 is ps8640 dsi input port */
 	in_ep = of_graph_get_endpoint_by_regs(dev->of_node, 0, -1);
 	if (!in_ep)
-- 
2.28.0

[PATCH v2 4/5] drm/bridge: ps8640: Print an error if VDO control fails

[Enric Balletbo i Serra]

Print an error message inside ps8640_bridge_vdo_control() function when
it fails so we can simplify a bit the callers, they will only need to
check the error code.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
---

Changes in v2: None

 drivers/gpu/drm/bridge/parade-ps8640.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index ce3e8b2da8c9..9f7b7a9c53c5 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -82,8 +82,11 @@ static int ps8640_bridge_vdo_control(struct ps8640 *ps_bridge,
 	ret = i2c_smbus_write_i2c_block_data(client, PAGE3_SET_ADD,
 					     sizeof(vdo_ctrl_buf),
 					     vdo_ctrl_buf);
-	if (ret < 0)
+	if (ret < 0) {
+		DRM_ERROR("failed to %sable VDO: %d\n",
+			  ctrl == ENABLE ? "en" : "dis", ret);
 		return ret;
+	}
 
 	return 0;
 }
@@ -150,10 +153,8 @@ static void ps8640_pre_enable(struct drm_bridge *bridge)
 	}
 
 	ret = ps8640_bridge_vdo_control(ps_bridge, ENABLE);
-	if (ret) {
-		DRM_ERROR("failed to enable VDO: %d\n", ret);
+	if (ret)
 		goto err_regulators_disable;
-	}
 
 	/* Switch access edp panel's edid through i2c */
 	ret = i2c_smbus_write_byte_data(client, PAGE2_I2C_BYPASS,
@@ -175,9 +176,7 @@ static void ps8640_post_disable(struct drm_bridge *bridge)
 	struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
 	int ret;
 
-	ret = ps8640_bridge_vdo_control(ps_bridge, DISABLE);
-	if (ret < 0)
-		DRM_ERROR("failed to disable VDO: %d\n", ret);
+	ps8640_bridge_vdo_control(ps_bridge, DISABLE);
 
 	gpiod_set_value(ps_bridge->gpio_reset, 1);
 	gpiod_set_value(ps_bridge->gpio_powerdown, 1);
-- 
2.28.0

[PATCH v2 5/5] drm/bridge: ps8640: Rework power state handling

[Enric Balletbo i Serra]

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>
---

Changes in v2:
- Use drm_bridge_chain_pre_enable/post_disable() helpers (Sam Ravnborg)

 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 = {
-- 
2.28.0

Re: [PATCH v2 1/5] drm/bridge_connector: Set default status connected for eDP connectors

[Bilal Wasim]

On Wed, 26 Aug 2020 10:15:22 +0200
Enric Balletbo i Serra <enric.balletbo@collabora.com> wrote:

> In an eDP application, HPD is not required and on most bridge chips
> useless. If HPD is not used, we need to set initial status as
> connected, otherwise the connector created by the
> drm_bridge_connector API remains in an unknown state.
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Acked-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> 
> Changes in v2:
> - Included the patch `drm/bridge_connector: Set default status
> connected for eDP connectors`
> 
>  drivers/gpu/drm/drm_bridge_connector.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/drm_bridge_connector.c
> b/drivers/gpu/drm/drm_bridge_connector.c index
> c6994fe673f3..a58cbde59c34 100644 ---
> a/drivers/gpu/drm/drm_bridge_connector.c +++
> b/drivers/gpu/drm/drm_bridge_connector.c @@ -187,6 +187,7 @@
> drm_bridge_connector_detect(struct drm_connector *connector, bool
> force) case DRM_MODE_CONNECTOR_DPI: case DRM_MODE_CONNECTOR_LVDS:
>  		case DRM_MODE_CONNECTOR_DSI:
> +		case DRM_MODE_CONNECTOR_eDP:
>  			status = connector_status_connected;
>  			break;
>  		default:

Reviewed-by: Bilal Wasim <bwasim.lkml@gmail.com>
Tested-by: Bilal Wasim <bwasim.lkml@gmail.com>

-Bilal

Re: [PATCH v2 3/5] drm/bridge: ps8640: Return an error for incorrect attach flags

[Bilal Wasim]

On Wed, 26 Aug 2020 10:15:24 +0200
Enric Balletbo i Serra <enric.balletbo@collabora.com> wrote:

> Bridge drivers that implement the new model only shall return an error
> from their attach() handler when the DRM_BRIDGE_ATTACH_NO_CONNECTOR
> flag is not set. So make sure we return an error because only the new
> drm_bridge model is supported.
> 
> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> 
> Changes in v2: None
> 
>  drivers/gpu/drm/bridge/parade-ps8640.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c
> b/drivers/gpu/drm/bridge/parade-ps8640.c index
> 13755d278db6..ce3e8b2da8c9 100644 ---
> a/drivers/gpu/drm/bridge/parade-ps8640.c +++
> b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -200,6 +200,10 @@ static
> int ps8640_bridge_attach(struct drm_bridge *bridge, .channel = 0,
>  						   .node = NULL,
>  						 };
> +
> +	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
> +		return -EINVAL;
> +
>  	/* port@0 is ps8640 dsi input port */
>  	in_ep = of_graph_get_endpoint_by_regs(dev->of_node, 0, -1);
>  	if (!in_ep)

Reviewed-by: Bilal Wasim <bwasim.lkml@gmail.com>
Tested-by: Bilal Wasim <bwasim.lkml@gmail.com>

-Bilal

Re: [PATCH v2 4/5] drm/bridge: ps8640: Print an error if VDO control fails

[Bilal Wasim]

On Wed, 26 Aug 2020 10:15:25 +0200
Enric Balletbo i Serra <enric.balletbo@collabora.com> wrote:

> Print an error message inside ps8640_bridge_vdo_control() function
> when it fails so we can simplify a bit the callers, they will only
> need to check the error code.
> 
> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> 
> Changes in v2: None
> 
>  drivers/gpu/drm/bridge/parade-ps8640.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c
> b/drivers/gpu/drm/bridge/parade-ps8640.c index
> ce3e8b2da8c9..9f7b7a9c53c5 100644 ---
> a/drivers/gpu/drm/bridge/parade-ps8640.c +++
> b/drivers/gpu/drm/bridge/parade-ps8640.c @@ -82,8 +82,11 @@ static
> int ps8640_bridge_vdo_control(struct ps8640 *ps_bridge, ret =
> i2c_smbus_write_i2c_block_data(client, PAGE3_SET_ADD,
> sizeof(vdo_ctrl_buf), vdo_ctrl_buf);
> -	if (ret < 0)
> +	if (ret < 0) {
> +		DRM_ERROR("failed to %sable VDO: %d\n",
> +			  ctrl == ENABLE ? "en" : "dis", ret);
>  		return ret;
> +	}
>  
>  	return 0;
>  }
> @@ -150,10 +153,8 @@ static void ps8640_pre_enable(struct drm_bridge
> *bridge) }
>  
>  	ret = ps8640_bridge_vdo_control(ps_bridge, ENABLE);
> -	if (ret) {
> -		DRM_ERROR("failed to enable VDO: %d\n", ret);
> +	if (ret)
>  		goto err_regulators_disable;
> -	}
>  
>  	/* Switch access edp panel's edid through i2c */
>  	ret = i2c_smbus_write_byte_data(client, PAGE2_I2C_BYPASS,
> @@ -175,9 +176,7 @@ static void ps8640_post_disable(struct drm_bridge
> *bridge) struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
>  	int ret;
>  
> -	ret = ps8640_bridge_vdo_control(ps_bridge, DISABLE);
> -	if (ret < 0)
> -		DRM_ERROR("failed to disable VDO: %d\n", ret);
> +	ps8640_bridge_vdo_control(ps_bridge, DISABLE);
>  
>  	gpiod_set_value(ps_bridge->gpio_reset, 1);
>  	gpiod_set_value(ps_bridge->gpio_powerdown, 1);

Reviewed-by: Bilal Wasim <bwasim.lkml@gmail.com>
Tested-by: Bilal Wasim <bwasim.lkml@gmail.com>

-Bilal

Re: [PATCH v2 5/5] drm/bridge: ps8640: Rework power state handling

[Bilal Wasim]

On Wed, 26 Aug 2020 10:15:26 +0200
Enric Balletbo i Serra <enric.balletbo@collabora.com> wrote:

> 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>
> ---
> 
> Changes in v2:
> - Use drm_bridge_chain_pre_enable/post_disable() helpers (Sam
> Ravnborg)
> 
>  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);

Is it safe for a bridge driver to enable power to other devices in the
bridge? Seems somewhat counter-intuitive, though I understand that the
complete chain needs to be enabled before getting EDID in this case.
Can we consider a more generic solution where the DRM stack enables the
bridge-chain before invoking calls to get EDID based on a DT-binding or
Kconfig option?

Also shouldn't the call to pre_enable be followed by a call to
"drm_bridge_chain_enable"? Similarly we should do both
drm_bridge_chain_post_disable / *_disable when
powering the chips off, right?

>  
> -	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 = {

-Bilal

Re: [PATCH v2 0/5] drm/bridge: ps8640: Make sure all needed is powered to get the EDID

[Sam Ravnborg]

Hi Enric

On Wed, Aug 26, 2020 at 10:15:21AM +0200, Enric Balletbo i Serra wrote:
> The first patch was initially part of the series [1] but for some reason
> was not picked when the series were merged, so I included in this series
> because it is needed to make the others to work properly.
> 
> The same happened for the second patch, was part of series [1] but not
> merged.
> 
> The third patch and next are part of the original series and are to rework
> the power handling to get the EDID. Basically, we need to make sure all the
> needed is powered to be able to get the EDID. Before, we saw that getting
> the EDID failed as explained in the third patch.
> 
> [1] https://lkml.org/lkml/2020/6/15/1208
> 
> Changes in v2:
> - Included the patch `drm/bridge_connector: Set default status connected for eDP connectors`
> - Included the patch `drm/bridge: ps8640: Get the EDID from eDP control`
> - Use drm_bridge_chain_pre_enable/post_disable() helpers (Sam Ravnborg)
> 
> Enric Balletbo i Serra (5):
>   drm/bridge_connector: Set default status connected for eDP connectors
>   drm/bridge: ps8640: Get the EDID from eDP control
>   drm/bridge: ps8640: Return an error for incorrect attach flags
>   drm/bridge: ps8640: Print an error if VDO control fails
The first 4 patches are applied to drm-misc-next.

>   drm/bridge: ps8640: Rework power state handling
Let give this a copuple of days on the mailing list to see what we
conclude.

	Sam
> 
>  drivers/gpu/drm/bridge/parade-ps8640.c | 89 ++++++++++++++++++++++----
>  drivers/gpu/drm/drm_bridge_connector.c |  1 +
>  2 files changed, 79 insertions(+), 11 deletions(-)
> 
> -- 
> 2.28.0

Re: [PATCH v2 5/5] drm/bridge: ps8640: Rework power state handling

[Sam Ravnborg]

Hi Enric.

On Wed, Aug 26, 2020 at 10:15:26AM +0200, Enric Balletbo i Serra wrote:
> 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>
> ---
> 
> Changes in v2:
> - Use drm_bridge_chain_pre_enable/post_disable() helpers (Sam Ravnborg)
> 
>  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);
> +}

The impleimentation of ps8640_bridge_poweron() versus
ps8640_bridge_poweroff() is confusing.

ps8640_bridge_poweron() includes ps8640_bridge_vdo_control(.., ENABLE),
but ps8640_bridge_poweroff() does not include
ps8640_bridge_vdo_control(..., DISABLE).

This is inconsistent and confusing. At least it was for me when
reviewing. Can this be improved - or maybe just use naming that does not
indicate they are the reverse of each other?

> +
> +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;
>  }

The use of drm_bridge_chain_pre_enable() and
drm_bridge_chain_post_disable() was exactly what I was asking for -
looks good.

I have not really considered the idea from Balil that we should provide
better infrastructure support powering on the bridge chain when reading
the edid. Maybe an idea for later?

	Sam



>  
>  static const struct drm_bridge_funcs ps8640_bridge_funcs = {
> -- 
> 2.28.0

Re: [PATCH v2 5/5] drm/bridge: ps8640: Rework power state handling

[Enric Balletbo i Serra]

Hi Sam,

Thanks for your comments.

On 26/8/20 20:46, Sam Ravnborg wrote:
> Hi Enric.
> 
> On Wed, Aug 26, 2020 at 10:15:26AM +0200, Enric Balletbo i Serra wrote:
>> 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>
>> ---
>>
>> Changes in v2:
>> - Use drm_bridge_chain_pre_enable/post_disable() helpers (Sam Ravnborg)
>>
>>  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);
>> +}
> 
> The impleimentation of ps8640_bridge_poweron() versus
> ps8640_bridge_poweroff() is confusing.
> 
> ps8640_bridge_poweron() includes ps8640_bridge_vdo_control(.., ENABLE),
> but ps8640_bridge_poweroff() does not include
> ps8640_bridge_vdo_control(..., DISABLE).
> 
> This is inconsistent and confusing. At least it was for me when
> reviewing. Can this be improved - or maybe just use naming that does not
> indicate they are the reverse of each other?
> 

Right, I think I can implement reverse of each other. So I'll send an updated
series.

Thanks,
 Enric

>> +
>> +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;
>>  }
> 
> The use of drm_bridge_chain_pre_enable() and
> drm_bridge_chain_post_disable() was exactly what I was asking for -
> looks good.
> 
> I have not really considered the idea from Balil that we should provide
> better infrastructure support powering on the bridge chain when reading
> the edid. Maybe an idea for later?
> 
> 	Sam
> 
> 
> 
>>  
>>  static const struct drm_bridge_funcs ps8640_bridge_funcs = {
>> -- 
>> 2.28.0
>