[PATCH v2 0/2] Support DRM bridges on NVIDIA Tegra

[PATCH v2 0/2] Support DRM bridges on NVIDIA Tegra

[Dmitry Osipenko]

Hello,

This small series adds initial support for the DRM bridges to NVIDIA Tegra
DRM driver. This is required by newer device-trees where we model the LVDS
encoder bridge properly.

Please note that the first "Support DRM bridges" patch was previously sent
out as a standalone v1 change.

Changelog:

v2: - Added the new "rgb: Don't register connector if bridge is used"
      patch, which hides the unused connector provided by the Tegra DRM
      driver when bridge is used, since bridge provides its own connector
      to us.

Dmitry Osipenko (2):
  drm/tegra: output: Support DRM bridges
  drm/tegra: output: rgb: Don't register connector if bridge is used

 drivers/gpu/drm/tegra/drm.h    |  2 ++
 drivers/gpu/drm/tegra/output.c | 25 ++++++++++++++++++++++++-
 drivers/gpu/drm/tegra/rgb.c    | 21 ++++++++++++++++-----
 3 files changed, 42 insertions(+), 6 deletions(-)

-- 
2.26.0

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[PATCH v2 1/2] drm/tegra: output: Support DRM bridges

[Dmitry Osipenko]

Newer Tegra device-trees will define a video output graph which involves
a bridge. This patch adds support for the DRM bridges to the Tegra's DRM
output.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/gpu/drm/tegra/drm.h    |  2 ++
 drivers/gpu/drm/tegra/output.c | 25 ++++++++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
index ed99b67deb29..9ca11989679c 100644
--- a/drivers/gpu/drm/tegra/drm.h
+++ b/drivers/gpu/drm/tegra/drm.h
@@ -16,6 +16,7 @@
 #include <drm/drm_encoder.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_fixed.h>
+#include <drm/drm_of.h>
 #include <drm/drm_probe_helper.h>
 #include <uapi/drm/tegra_drm.h>
 
@@ -116,6 +117,7 @@ struct tegra_output {
 	struct device_node *of_node;
 	struct device *dev;
 
+	struct drm_bridge *bridge;
 	struct drm_panel *panel;
 	struct i2c_adapter *ddc;
 	const struct edid *edid;
diff --git a/drivers/gpu/drm/tegra/output.c b/drivers/gpu/drm/tegra/output.c
index a264259b97a2..6b8fae4659b4 100644
--- a/drivers/gpu/drm/tegra/output.c
+++ b/drivers/gpu/drm/tegra/output.c
@@ -96,13 +96,28 @@ static irqreturn_t hpd_irq(int irq, void *data)
 
 int tegra_output_probe(struct tegra_output *output)
 {
-	struct device_node *ddc, *panel;
+	struct device_node *ddc, *panel, *port;
 	unsigned long flags;
 	int err, size;
 
 	if (!output->of_node)
 		output->of_node = output->dev->of_node;
 
+	/* newer device-trees may utilize output graph */
+	port = of_get_child_by_name(output->of_node, "port");
+	if (port) {
+		err = drm_of_find_panel_or_bridge(output->of_node, 0, 0,
+						  &output->panel,
+						  &output->bridge);
+		of_node_put(port);
+		if (err)
+			return err;
+	}
+
+	if (output->panel || output->bridge)
+		goto edid_property;
+
+	/* for older device-trees we fall back to nvidia,panel */
 	panel = of_parse_phandle(output->of_node, "nvidia,panel", 0);
 	if (panel) {
 		output->panel = of_drm_find_panel(panel);
@@ -112,6 +127,7 @@ int tegra_output_probe(struct tegra_output *output)
 		of_node_put(panel);
 	}
 
+edid_property:
 	output->edid = of_get_property(output->of_node, "nvidia,edid", &size);
 
 	ddc = of_parse_phandle(output->of_node, "nvidia,ddc-i2c-bus", 0);
@@ -189,6 +205,13 @@ int tegra_output_init(struct drm_device *drm, struct tegra_output *output)
 		err = drm_panel_attach(output->panel, &output->connector);
 		if (err < 0)
 			return err;
+	} else if (output->bridge) {
+		err = drm_bridge_attach(&output->encoder, output->bridge,
+					NULL, 0);
+		if (err) {
+			dev_err(drm->dev, "cannot connect bridge: %d\n", err);
+			return err;
+		}
 	}
 
 	/*
-- 
2.26.0

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[PATCH v2 2/2] drm/tegra: output: rgb: Don't register connector if bridge is used

[Dmitry Osipenko]

We rely on the connector that is created by the bridge, and thus, the
Tegra's output connector is not needed in this case because it will be
an unused connector.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/gpu/drm/tegra/rgb.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c
index 4be4dfd4a68a..6e6b3fee1d87 100644
--- a/drivers/gpu/drm/tegra/rgb.c
+++ b/drivers/gpu/drm/tegra/rgb.c
@@ -275,21 +275,32 @@ int tegra_dc_rgb_init(struct drm_device *drm, struct tegra_dc *dc)
 	if (!dc->rgb)
 		return -ENODEV;
 
+	drm_encoder_init(drm, &output->encoder, &tegra_rgb_encoder_funcs,
+			 DRM_MODE_ENCODER_LVDS, NULL);
+	drm_encoder_helper_add(&output->encoder,
+			       &tegra_rgb_encoder_helper_funcs);
+
+	/*
+	 * We don't create a parent "output bridge" that sets the
+	 * DRM_BRIDGE_ATTACH_NO_CONNECTOR flag for drm_bridge_attach(),
+	 * and thus, the bridge creates connector for us in this case.
+	 * The output's connector is unused and not needed if bridge is
+	 * used, so skip the connector's registration in this case.
+	 */
+	if (output->bridge)
+		goto init_output;
+
 	drm_connector_init(drm, &output->connector, &tegra_rgb_connector_funcs,
 			   DRM_MODE_CONNECTOR_LVDS);
 	drm_connector_helper_add(&output->connector,
 				 &tegra_rgb_connector_helper_funcs);
 	output->connector.dpms = DRM_MODE_DPMS_OFF;
 
-	drm_encoder_init(drm, &output->encoder, &tegra_rgb_encoder_funcs,
-			 DRM_MODE_ENCODER_LVDS, NULL);
-	drm_encoder_helper_add(&output->encoder,
-			       &tegra_rgb_encoder_helper_funcs);
-
 	drm_connector_attach_encoder(&output->connector,
 					  &output->encoder);
 	drm_connector_register(&output->connector);
 
+init_output:
 	err = tegra_output_init(drm, output);
 	if (err < 0) {
 		dev_err(output->dev, "failed to initialize output: %d\n", err);
-- 
2.26.0

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Re: [PATCH v2 0/2] Support DRM bridges on NVIDIA Tegra

[Sam Ravnborg]

Hi Dimitry.

Added Laurent that is the arthitecht behind the new bridge model
briefly explained below.

On Wed, Apr 15, 2020 at 01:20:05AM +0300, Dmitry Osipenko wrote:
> Hello,
> 
> This small series adds initial support for the DRM bridges to NVIDIA Tegra
> DRM driver. This is required by newer device-trees where we model the LVDS
> encoder bridge properly.
> 
> Please note that the first "Support DRM bridges" patch was previously sent
> out as a standalone v1 change.
> 
> Changelog:
> 
> v2: - Added the new "rgb: Don't register connector if bridge is used"
>       patch, which hides the unused connector provided by the Tegra DRM
>       driver when bridge is used, since bridge provides its own connector
>       to us.

We are moving to a model where the display driver have the
responsibility to create the connector - not the bridge.

The flags argument to:

    drm_bridge_attach(encoder, bridge, previous, flags);

is used to tell if the brigde shall create the connector or the display
driver does it - DRM_BRIDGE_ATTACH_NO_CONNECTOR.

It would be preferred that we moved the relevant bridge drivers to the
new model no so you did not need to support the old model in the driver.

If you help identify the bridge drivers we could migrate them to the new
model and you could help testing?

What bridge drivers will be used for tegra?

	Sam
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Re: [PATCH v2 0/2] Support DRM bridges on NVIDIA Tegra

[Dmitry Osipenko]

15.04.2020 12:53, Sam Ravnborg пишет:
> Hi Dimitry.
> 
> Added Laurent that is the arthitecht behind the new bridge model
> briefly explained below.
> 
> On Wed, Apr 15, 2020 at 01:20:05AM +0300, Dmitry Osipenko wrote:
>> Hello,
>>
>> This small series adds initial support for the DRM bridges to NVIDIA Tegra
>> DRM driver. This is required by newer device-trees where we model the LVDS
>> encoder bridge properly.
>>
>> Please note that the first "Support DRM bridges" patch was previously sent
>> out as a standalone v1 change.
>>
>> Changelog:
>>
>> v2: - Added the new "rgb: Don't register connector if bridge is used"
>>       patch, which hides the unused connector provided by the Tegra DRM
>>       driver when bridge is used, since bridge provides its own connector
>>       to us.
> 
> We are moving to a model where the display driver have the
> responsibility to create the connector - not the bridge.
> 
> The flags argument to:
> 
>     drm_bridge_attach(encoder, bridge, previous, flags);
> 
> is used to tell if the brigde shall create the connector or the display
> driver does it - DRM_BRIDGE_ATTACH_NO_CONNECTOR.
> 
> It would be preferred that we moved the relevant bridge drivers to the
> new model no so you did not need to support the old model in the driver.

Hello Sam,

Thank you very much for the clarification! To be honest, I was a bit
confused by the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag.

Perhaps would be nice if the code told explicitly that drivers should
use the new flag because it appeared to me that adding bridge functions
to the DRM driver is a step backwards since looks like it involves
writing some more code :)

> If you help identify the bridge drivers we could migrate them to the new
> model and you could help testing?
> 
> What bridge drivers will be used for tegra?

It's lvds-encoder of bridge/lvds-codec.c, which supports the new model.

I'll try to move to the new model in v3. Thanks again!
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