[PATCH 0/8] Add a panel API to return panel orientation

[PATCH 0/8] Add a panel API to return panel orientation

[Hsin-Yi Wang]

Panels usually call drm_connector_set_panel_orientation(), which is
later than drm/kms driver calling drm_dev_register(). This leads to a
WARN()[1].

The orientation property is known earlier. For example, some panels
parse the property through device tree during probe.

The series add a panel API drm_panel_get_orientation() for drm/kms
drivers. The drivers can use the API to get panel's orientation, so they
can call drm_connector_set_panel_orientation() before drm_dev_register().

Panel needs to implement .get_orientation callback to return the property.

[1] https://patchwork.kernel.org/project/linux-mediatek/patch/20220530081910.3947168-2-hsinyi@chromium.org/

Hsin-Yi Wang (8):
  drm/panel: Add an API drm_panel_get_orientation() to return panel
    orientation
  drm/panel: boe-tv101wum-nl6: Implement .get_orientation callback
  drm/panel: panel-edp: Implement .get_orientation callback
  drm/panel: lvds: Implement .get_orientation callback
  drm/panel: panel-simple: Implement .get_orientation callback
  drm/panel: ili9881c: Implement .get_orientation callback
  drm/panel: elida-kd35t133: Implement .get_orientation callback
  drm/mediatek: Config orientation property if panel provides it

 drivers/gpu/drm/drm_panel.c                    |  8 ++++++++
 drivers/gpu/drm/mediatek/mtk_dsi.c             | 14 ++++++++++++++
 drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c |  8 ++++++++
 drivers/gpu/drm/panel/panel-edp.c              |  8 ++++++++
 drivers/gpu/drm/panel/panel-elida-kd35t133.c   |  8 ++++++++
 drivers/gpu/drm/panel/panel-ilitek-ili9881c.c  |  8 ++++++++
 drivers/gpu/drm/panel/panel-lvds.c             |  8 ++++++++
 drivers/gpu/drm/panel/panel-simple.c           |  9 +++++++++
 include/drm/drm_panel.h                        | 10 ++++++++++
 9 files changed, 81 insertions(+)

-- 
2.36.1.255.ge46751e96f-goog

[PATCH 1/8] drm/panel: Add an API drm_panel_get_orientation() to return panel orientation

[Hsin-Yi Wang]

Panels usually call drm_connector_set_panel_orientation(), which is
later than drm/kms driver calling drm_dev_register(). This leads to a
WARN().

The orientation property is known earlier. For example, some panels
parse the property through device tree during probe.

Add an API to return the property from panel to drm/kms driver, so the
drivers are able to call drm_connector_set_panel_orientation() before
drm_dev_register().

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
Previous discussion:
https://patchwork.kernel.org/project/linux-mediatek/cover/20220530081910.3947168-1-hsinyi@chromium.org/#24877477
---
 drivers/gpu/drm/drm_panel.c |  8 ++++++++
 include/drm/drm_panel.h     | 10 ++++++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index f634371c717a..4a512ca80673 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -223,6 +223,14 @@ int drm_panel_get_modes(struct drm_panel *panel,
 }
 EXPORT_SYMBOL(drm_panel_get_modes);
 
+enum drm_panel_orientation drm_panel_get_orientation(struct drm_panel *panel)
+{
+	if (panel && panel->funcs && panel->funcs->get_orientation)
+		return panel->funcs->get_orientation(panel);
+
+	return DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
+}
+EXPORT_SYMBOL(drm_panel_get_orientation);
 #ifdef CONFIG_OF
 /**
  * of_drm_find_panel - look up a panel using a device tree node
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 1ba2d424a53f..d1bd3be4bbdf 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -133,6 +133,15 @@ struct drm_panel_funcs {
 	 * Allows panels to create panels-specific debugfs files.
 	 */
 	void (*debugfs_init)(struct drm_panel *panel, struct dentry *root);
+
+	/**
+	 * @get_orientation:
+	 *
+	 * Return the panel orientation set by device tree or EDID.
+	 *
+	 * This function is optional.
+	 */
+	enum drm_panel_orientation (*get_orientation)(struct drm_panel *panel);
 };
 
 /**
@@ -195,6 +204,7 @@ int drm_panel_enable(struct drm_panel *panel);
 int drm_panel_disable(struct drm_panel *panel);
 
 int drm_panel_get_modes(struct drm_panel *panel, struct drm_connector *connector);
+enum drm_panel_orientation drm_panel_get_orientation(struct drm_panel *panel);
 
 #if defined(CONFIG_OF) && defined(CONFIG_DRM_PANEL)
 struct drm_panel *of_drm_find_panel(const struct device_node *np);
-- 
2.36.1.255.ge46751e96f-goog

[PATCH 2/8] drm/panel: boe-tv101wum-nl6: Implement .get_orientation callback

[Hsin-Yi Wang]

To return the orientation property to drm/kms driver.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c b/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
index 1be150ac758f..0f1c9b685da3 100644
--- a/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
+++ b/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
@@ -1516,11 +1516,19 @@ static int boe_panel_get_modes(struct drm_panel *panel,
 	return 1;
 }
 
+static enum drm_panel_orientation boe_panel_get_orientation(struct drm_panel *panel)
+{
+	struct boe_panel *boe = to_boe_panel(panel);
+
+	return boe->orientation;
+}
+
 static const struct drm_panel_funcs boe_panel_funcs = {
 	.unprepare = boe_panel_unprepare,
 	.prepare = boe_panel_prepare,
 	.enable = boe_panel_enable,
 	.get_modes = boe_panel_get_modes,
+	.get_orientation = boe_panel_get_orientation,
 };
 
 static int boe_panel_add(struct boe_panel *boe)
-- 
2.36.1.255.ge46751e96f-goog

[PATCH 3/8] drm/panel: panel-edp: Implement .get_orientation callback

[Hsin-Yi Wang]

To return the orientation property to drm/kms driver.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 drivers/gpu/drm/panel/panel-edp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
index 1732b4f56e38..a2133581a72d 100644
--- a/drivers/gpu/drm/panel/panel-edp.c
+++ b/drivers/gpu/drm/panel/panel-edp.c
@@ -609,6 +609,13 @@ static int panel_edp_get_timings(struct drm_panel *panel,
 	return p->desc->num_timings;
 }
 
+static enum drm_panel_orientation panel_edp_get_orientation(struct drm_panel *panel)
+{
+	struct panel_edp *p = to_panel_edp(panel);
+
+       return p->orientation;
+}
+
 static int detected_panel_show(struct seq_file *s, void *data)
 {
 	struct drm_panel *panel = s->private;
@@ -637,6 +644,7 @@ static const struct drm_panel_funcs panel_edp_funcs = {
 	.prepare = panel_edp_prepare,
 	.enable = panel_edp_enable,
 	.get_modes = panel_edp_get_modes,
+	.get_orientation = panel_edp_get_orientation,
 	.get_timings = panel_edp_get_timings,
 	.debugfs_init = panel_edp_debugfs_init,
 };
-- 
2.36.1.255.ge46751e96f-goog

[PATCH 4/8] drm/panel: lvds: Implement .get_orientation callback

[Hsin-Yi Wang]

To return the orientation property to drm/kms driver.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 drivers/gpu/drm/panel/panel-lvds.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-lvds.c b/drivers/gpu/drm/panel/panel-lvds.c
index 27a1c9923b09..dc50f73d400f 100644
--- a/drivers/gpu/drm/panel/panel-lvds.c
+++ b/drivers/gpu/drm/panel/panel-lvds.c
@@ -107,10 +107,18 @@ static int panel_lvds_get_modes(struct drm_panel *panel,
 	return 1;
 }
 
+static enum drm_panel_orientation panel_lvds_get_orientation,(struct drm_panel *panel)
+{
+       struct panel_lvds *lvds = to_panel_lvds(panel);
+
+       return lvds->orientation;
+}
+
 static const struct drm_panel_funcs panel_lvds_funcs = {
 	.unprepare = panel_lvds_unprepare,
 	.prepare = panel_lvds_prepare,
 	.get_modes = panel_lvds_get_modes,
+	.get_orientation = panel_lvds_get_orientation,
 };
 
 static int panel_lvds_parse_dt(struct panel_lvds *lvds)
-- 
2.36.1.255.ge46751e96f-goog

[PATCH 5/8] drm/panel: panel-simple: Implement .get_orientation callback

[Hsin-Yi Wang]

To return the orientation property to drm/kms driver.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 drivers/gpu/drm/panel/panel-simple.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index a34f4198a534..54e78d978dcb 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -434,6 +434,14 @@ static int panel_simple_get_timings(struct drm_panel *panel,
 	return p->desc->num_timings;
 }
 
+static enum drm_panel_orientation panel_simple_get_orientation(struct drm_panel *panel)
+{
+       struct panel_simple *p = to_panel_simple(panel);
+
+       return p->orientation;
+}
+
+
 static const struct drm_panel_funcs panel_simple_funcs = {
 	.disable = panel_simple_disable,
 	.unprepare = panel_simple_unprepare,
@@ -441,6 +449,7 @@ static const struct drm_panel_funcs panel_simple_funcs = {
 	.enable = panel_simple_enable,
 	.get_modes = panel_simple_get_modes,
 	.get_timings = panel_simple_get_timings,
+	.get_orientation = panel_simple_get_orientation,
 };
 
 static struct panel_desc panel_dpi;
-- 
2.36.1.255.ge46751e96f-goog

[PATCH 6/8] drm/panel: ili9881c: Implement .get_orientation callback

[Hsin-Yi Wang]

To return the orientation property to drm/kms driver.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
index ba30d11547ad..238b6a75d2ed 100644
--- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
+++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
@@ -858,12 +858,20 @@ static int ili9881c_get_modes(struct drm_panel *panel,
 	return 1;
 }
 
+static enum drm_panel_orientation ili9881c_get_orientation(struct drm_panel *panel)
+{
+       struct ili9881c *ctx = panel_to_ili9881c(panel);
+
+       return ctx->orientation;
+}
+
 static const struct drm_panel_funcs ili9881c_funcs = {
 	.prepare	= ili9881c_prepare,
 	.unprepare	= ili9881c_unprepare,
 	.enable		= ili9881c_enable,
 	.disable	= ili9881c_disable,
 	.get_modes	= ili9881c_get_modes,
+	.get_orientation = ili9881c_get_orientation,
 };
 
 static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi)
-- 
2.36.1.255.ge46751e96f-goog

[PATCH 7/8] drm/panel: elida-kd35t133: Implement .get_orientation callback

[Hsin-Yi Wang]

To return the orientation property to drm/kms driver.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 drivers/gpu/drm/panel/panel-elida-kd35t133.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-elida-kd35t133.c b/drivers/gpu/drm/panel/panel-elida-kd35t133.c
index 80227617a4d6..079ed71f660c 100644
--- a/drivers/gpu/drm/panel/panel-elida-kd35t133.c
+++ b/drivers/gpu/drm/panel/panel-elida-kd35t133.c
@@ -222,10 +222,18 @@ static int kd35t133_get_modes(struct drm_panel *panel,
 	return 1;
 }
 
+static enum drm_panel_orientation kd35t133_get_orientation(struct drm_panel *panel)
+{
+       struct kd35t133 *ctx = panel_to_kd35t133(panel);
+
+       return ctx->orientation;
+}
+
 static const struct drm_panel_funcs kd35t133_funcs = {
 	.unprepare	= kd35t133_unprepare,
 	.prepare	= kd35t133_prepare,
 	.get_modes	= kd35t133_get_modes,
+	.get_orientation = kd35t133_get_orientation,
 };
 
 static int kd35t133_probe(struct mipi_dsi_device *dsi)
-- 
2.36.1.255.ge46751e96f-goog

[PATCH 8/8] drm/mediatek: Config orientation property if panel provides it

[Hsin-Yi Wang]

Panel orientation property should be set before drm_dev_register().
Mediatek drm driver calls drm_dev_register() in .bind(). However, most
panels sets orientation property relatively late, mostly in .get_modes()
callback, since this is when they are able to get the connector and
binds the orientation property to it, though the value should be known
when the panel is probed.

Let the drm driver check if the remote end point is a panel and if it
contains the orientation property. If it does, set it before
drm_dev_register() is called.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
The concept is the same as the previous version.
https://patchwork.kernel.org/project/linux-mediatek/patch/20220530113033.124072-1-hsinyi@chromium.org/
The only difference is, it now uses the panel API instead of parsing
orientation from the driver.
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index bd3f5b485085..12836a697f56 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -185,6 +185,7 @@ struct mtk_dsi {
 	struct drm_encoder encoder;
 	struct drm_bridge bridge;
 	struct drm_bridge *next_bridge;
+	struct drm_panel *panel;
 	struct drm_connector *connector;
 	struct phy *phy;
 
@@ -822,6 +823,16 @@ static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
 		ret = PTR_ERR(dsi->connector);
 		goto err_cleanup_encoder;
 	}
+
+	/* Read panel orientation */
+	if (dsi->panel) {
+		enum drm_panel_orientation orientation;
+
+		orientation = drm_panel_get_orientation(dsi->panel);
+		if (orientation != DRM_MODE_PANEL_ORIENTATION_UNKNOWN)
+			drm_connector_set_panel_orientation(dsi->connector, orientation);
+	}
+
 	drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
 
 	return 0;
@@ -837,6 +848,9 @@ static int mtk_dsi_bind(struct device *dev, struct device *master, void *data)
 	struct drm_device *drm = data;
 	struct mtk_dsi *dsi = dev_get_drvdata(dev);
 
+	/* Get panel if existed */
+	ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0, &dsi->panel, NULL);
+
 	ret = mtk_dsi_encoder_init(drm, dsi);
 	if (ret)
 		return ret;
-- 
2.36.1.255.ge46751e96f-goog

Re: [PATCH 0/8] Add a panel API to return panel orientation

[Hans de Goede]

Hi,

On 6/1/22 10:18, Hsin-Yi Wang wrote:
> Panels usually call drm_connector_set_panel_orientation(), which is
> later than drm/kms driver calling drm_dev_register(). This leads to a
> WARN()[1].
> 
> The orientation property is known earlier. For example, some panels
> parse the property through device tree during probe.
> 
> The series add a panel API drm_panel_get_orientation() for drm/kms
> drivers. The drivers can use the API to get panel's orientation, so they
> can call drm_connector_set_panel_orientation() before drm_dev_register().
> 
> Panel needs to implement .get_orientation callback to return the property.
> 
> [1] https://patchwork.kernel.org/project/linux-mediatek/patch/20220530081910.3947168-2-hsinyi@chromium.org/

Thank you for implementing this.

Patches 1-7 look good to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

I've a few small remarks on patch 8, see my reply
to that patch.

Regards,

Hans


> 
> Hsin-Yi Wang (8):
>   drm/panel: Add an API drm_panel_get_orientation() to return panel
>     orientation
>   drm/panel: boe-tv101wum-nl6: Implement .get_orientation callback
>   drm/panel: panel-edp: Implement .get_orientation callback
>   drm/panel: lvds: Implement .get_orientation callback
>   drm/panel: panel-simple: Implement .get_orientation callback
>   drm/panel: ili9881c: Implement .get_orientation callback
>   drm/panel: elida-kd35t133: Implement .get_orientation callback
>   drm/mediatek: Config orientation property if panel provides it
> 
>  drivers/gpu/drm/drm_panel.c                    |  8 ++++++++
>  drivers/gpu/drm/mediatek/mtk_dsi.c             | 14 ++++++++++++++
>  drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c |  8 ++++++++
>  drivers/gpu/drm/panel/panel-edp.c              |  8 ++++++++
>  drivers/gpu/drm/panel/panel-elida-kd35t133.c   |  8 ++++++++
>  drivers/gpu/drm/panel/panel-ilitek-ili9881c.c  |  8 ++++++++
>  drivers/gpu/drm/panel/panel-lvds.c             |  8 ++++++++
>  drivers/gpu/drm/panel/panel-simple.c           |  9 +++++++++
>  include/drm/drm_panel.h                        | 10 ++++++++++
>  9 files changed, 81 insertions(+)
> 

Re: [PATCH 8/8] drm/mediatek: Config orientation property if panel provides it

[Hans de Goede]

Hi,

On 6/1/22 10:18, Hsin-Yi Wang wrote:
> Panel orientation property should be set before drm_dev_register().
> Mediatek drm driver calls drm_dev_register() in .bind(). However, most
> panels sets orientation property relatively late, mostly in .get_modes()
> callback, since this is when they are able to get the connector and
> binds the orientation property to it, though the value should be known
> when the panel is probed.
> 
> Let the drm driver check if the remote end point is a panel and if it
> contains the orientation property. If it does, set it before
> drm_dev_register() is called.
> 
> Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
> ---
> The concept is the same as the previous version.
> https://patchwork.kernel.org/project/linux-mediatek/patch/20220530113033.124072-1-hsinyi@chromium.org/
> The only difference is, it now uses the panel API instead of parsing
> orientation from the driver.
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index bd3f5b485085..12836a697f56 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -185,6 +185,7 @@ struct mtk_dsi {
>  	struct drm_encoder encoder;
>  	struct drm_bridge bridge;
>  	struct drm_bridge *next_bridge;
> +	struct drm_panel *panel;
>  	struct drm_connector *connector;
>  	struct phy *phy;
>  
> @@ -822,6 +823,16 @@ static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
>  		ret = PTR_ERR(dsi->connector);
>  		goto err_cleanup_encoder;
>  	}
> +
> +	/* Read panel orientation */
> +	if (dsi->panel) {
> +		enum drm_panel_orientation orientation;
> +
> +		orientation = drm_panel_get_orientation(dsi->panel);
> +		if (orientation != DRM_MODE_PANEL_ORIENTATION_UNKNOWN)
> +			drm_connector_set_panel_orientation(dsi->connector, orientation);
> +	}
> +
>  	drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
>  
>  	return 0;

drm_connector_set_panel_orientation() is a no-op when called with 
DRM_MODE_PANEL_ORIENTATION_UNKNOWN, so the check for this is not
necessary. This allows this to be simplified to:

	/* Read panel orientation */
	if (dsi->panel)
		drm_connector_set_panel_orientation(dsi->connector,
						    drm_panel_get_orientation(dsi->panel));


Note since drm_panel_get_orientation() checks for a NULL panel, you could even
drop the "if (dsi->panel)", but I think the meaning of the code is more
clear with that present.






> @@ -837,6 +848,9 @@ static int mtk_dsi_bind(struct device *dev, struct device *master, void *data)
>  	struct drm_device *drm = data;
>  	struct mtk_dsi *dsi = dev_get_drvdata(dev);
>  
> +	/* Get panel if existed */
> +	ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0, &dsi->panel, NULL);
> +

Check ret? or maybe not assign to ret ?    I understand some errors are expected
so maybe something like:

	if (ret && ret != -ENODEV)
		return ret;

?

Note -ENODEV is probably not the right error the check for!

Regards,

Hans



>  	ret = mtk_dsi_encoder_init(drm, dsi);
>  	if (ret)
>  		return ret;

Re: [PATCH 8/8] drm/mediatek: Config orientation property if panel provides it

[Hsin-Yi Wang]

On Wed, Jun 1, 2022 at 4:57 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Hi,
>
> On 6/1/22 10:18, Hsin-Yi Wang wrote:
> > Panel orientation property should be set before drm_dev_register().
> > Mediatek drm driver calls drm_dev_register() in .bind(). However, most
> > panels sets orientation property relatively late, mostly in .get_modes()
> > callback, since this is when they are able to get the connector and
> > binds the orientation property to it, though the value should be known
> > when the panel is probed.
> >
> > Let the drm driver check if the remote end point is a panel and if it
> > contains the orientation property. If it does, set it before
> > drm_dev_register() is called.
> >
> > Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
> > ---
> > The concept is the same as the previous version.
> > https://patchwork.kernel.org/project/linux-mediatek/patch/20220530113033.124072-1-hsinyi@chromium.org/
> > The only difference is, it now uses the panel API instead of parsing
> > orientation from the driver.
> > ---
> >  drivers/gpu/drm/mediatek/mtk_dsi.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > index bd3f5b485085..12836a697f56 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > @@ -185,6 +185,7 @@ struct mtk_dsi {
> >       struct drm_encoder encoder;
> >       struct drm_bridge bridge;
> >       struct drm_bridge *next_bridge;
> > +     struct drm_panel *panel;
> >       struct drm_connector *connector;
> >       struct phy *phy;
> >
> > @@ -822,6 +823,16 @@ static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
> >               ret = PTR_ERR(dsi->connector);
> >               goto err_cleanup_encoder;
> >       }
> > +
> > +     /* Read panel orientation */
> > +     if (dsi->panel) {
> > +             enum drm_panel_orientation orientation;
> > +
> > +             orientation = drm_panel_get_orientation(dsi->panel);
> > +             if (orientation != DRM_MODE_PANEL_ORIENTATION_UNKNOWN)
> > +                     drm_connector_set_panel_orientation(dsi->connector, orientation);
> > +     }
> > +
> >       drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
> >
> >       return 0;
>
> drm_connector_set_panel_orientation() is a no-op when called with
> DRM_MODE_PANEL_ORIENTATION_UNKNOWN, so the check for this is not
> necessary. This allows this to be simplified to:
>
>         /* Read panel orientation */
>         if (dsi->panel)
>                 drm_connector_set_panel_orientation(dsi->connector,
>                                                     drm_panel_get_orientation(dsi->panel));
>
>
> Note since drm_panel_get_orientation() checks for a NULL panel, you could even
> drop the "if (dsi->panel)", but I think the meaning of the code is more
> clear with that present.
>
Will update this
>
>
>
>
>
> > @@ -837,6 +848,9 @@ static int mtk_dsi_bind(struct device *dev, struct device *master, void *data)
> >       struct drm_device *drm = data;
> >       struct mtk_dsi *dsi = dev_get_drvdata(dev);
> >
> > +     /* Get panel if existed */
> > +     ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0, &dsi->panel, NULL);
> > +
>
> Check ret? or maybe not assign to ret ?    I understand some errors are expected
> so maybe something like:
>
>         if (ret && ret != -ENODEV)
>                 return ret;
>
I will choose not to assign ret. In some cases that the end point is a
bridge (not panel), since we assign NULL to the bridge, we will get
EPROBE_DEFER.

If the panel fails at this stage,
drm_connector_set_panel_orientation() is just a no-op. Let dsi still
be able to be binded.


> ?
>
> Note -ENODEV is probably not the right error the check for!
>
> Regards,
>
> Hans
>
>
>
> >       ret = mtk_dsi_encoder_init(drm, dsi);
> >       if (ret)
> >               return ret;
>