[PATCH v7 0/6] Support DRM bridges on NVIDIA Tegra

[PATCH v7 0/6] Support DRM bridges on NVIDIA Tegra

[Dmitry Osipenko]

Hello,

This 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.

Changelog:

v7: - Removed the obscure unused structs (which GCC doesn't detect, but CLANG
      does) in the patch "Wrap directly-connected panel into DRM bridge",
      which was reported by kernel test robot for v6.

v6: - Added r-b and acks from Rob Herring and Sam Ravnborg.

    - Rebased on a recent linux-next, patches now apply without fuzz.

v5: - Added new patches that make drm_of_find_panel_or_bridge() more usable
      if graph isn't defined in a device-tree:

        of_graph: add of_graph_get_local_port()
        drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

    - Updated "Support DRM bridges" patch to use drm_of_find_panel_or_bridge()
      directly and added WARN_ON(output->panel || output->bridge) sanity-check.

    - Added new "Wrap directly-connected panel into DRM bridge" patch, as
      was suggested by Laurent Pinchart.

v4: - Following review comments that were made by Laurent Pinchart to the v3,
      we now create and use the "bridge connector".

v3: - Following recommendation from Sam Ravnborg, the new bridge attachment
      model is now being used, i.e. we ask bridge to *not* create a connector
      using the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag.

    - The bridge is now created only for the RGB (LVDS) output, and only
      when necessary. For now we don't need bridges for HDMI or DSI outputs.

    - I noticed that we're leaking OF node in the panel's error code path,
      this is fixed now by the new patch "Don't leak OF node on error".

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 (6):
  of_graph: add of_graph_get_local_port()
  drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence
  drm/tegra: output: Don't leak OF node on error
  drm/tegra: output: Support DRM bridges
  drm/tegra: output: rgb: Support LVDS encoder bridge
  drm/tegra: output: rgb: Wrap directly-connected panel into DRM bridge

 drivers/gpu/drm/drm_of.c       |  13 ++++-
 drivers/gpu/drm/tegra/drm.h    |   2 +
 drivers/gpu/drm/tegra/output.c |  21 +++++--
 drivers/gpu/drm/tegra/rgb.c    | 102 +++++++++++++++++----------------
 drivers/of/property.c          |  32 ++++++++---
 include/linux/of_graph.h       |   7 +++
 6 files changed, 114 insertions(+), 63 deletions(-)

-- 
2.26.0

[PATCH v7 1/6] of_graph: add of_graph_get_local_port()

[Dmitry Osipenko]

In some case, like a DRM display code for example, it's useful to silently
check whether port node exists at all in a device-tree before proceeding
with parsing the graph.

This patch adds of_graph_get_local_port() which returns pointer to a local
port node, or NULL if graph isn't specified in a device-tree for a given
device node.

Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/of/property.c    | 32 +++++++++++++++++++++++---------
 include/linux/of_graph.h |  7 +++++++
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index 1f2086f4e7ce..05c5f619b8bb 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
 	 * parent port node.
 	 */
 	if (!prev) {
-		struct device_node *node;
-
-		node = of_get_child_by_name(parent, "ports");
-		if (node)
-			parent = node;
-
-		port = of_get_child_by_name(parent, "port");
-		of_node_put(node);
-
+		port = of_graph_get_local_port(parent);
 		if (!port) {
 			pr_err("graph: no port node found in %pOF\n", parent);
 			return NULL;
@@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
 }
 EXPORT_SYMBOL(of_graph_get_remote_port);
 
+/**
+ * of_graph_get_local_port() - get local port node
+ * @node: pointer to a local endpoint device_node
+ *
+ * Return: First local port node associated with local endpoint node linked
+ *	   to @node. Use of_node_put() on it when done.
+ */
+struct device_node *of_graph_get_local_port(const struct device_node *node)
+{
+	struct device_node *ports, *port;
+
+	ports = of_get_child_by_name(node, "ports");
+	if (ports)
+		node = ports;
+
+	port = of_get_child_by_name(node, "port");
+	of_node_put(ports);
+
+	return port;
+}
+EXPORT_SYMBOL(of_graph_get_local_port);
+
 int of_graph_get_endpoint_count(const struct device_node *np)
 {
 	struct device_node *endpoint;
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index 01038a6aade0..1fdeb72c7765 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -54,6 +54,7 @@ struct device_node *of_graph_get_remote_port_parent(
 struct device_node *of_graph_get_remote_port(const struct device_node *node);
 struct device_node *of_graph_get_remote_node(const struct device_node *node,
 					     u32 port, u32 endpoint);
+struct device_node *of_graph_get_local_port(const struct device_node *node);
 #else
 
 static inline int of_graph_parse_endpoint(const struct device_node *node,
@@ -116,6 +117,12 @@ static inline struct device_node *of_graph_get_remote_node(
 	return NULL;
 }
 
+static inline struct device_node *of_graph_get_local_port(
+					const struct device_node *node)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_OF */
 
 #endif /* __LINUX_OF_GRAPH_H */
-- 
2.26.0

[PATCH v7 2/6] drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

[Dmitry Osipenko]

When graph isn't defined in a device-tree, the of_graph_get_remote_node()
prints a noisy error message, telling that port node is not found. This is
undesirable behaviour in our case because absence of a panel/bridge graph
is a valid case. Let's check presence of the local port in a device-tree
before proceeding with parsing the graph.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/gpu/drm/drm_of.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index b50b44e76279..e0652c38f357 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -239,13 +239,24 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 				struct drm_bridge **bridge)
 {
 	int ret = -EPROBE_DEFER;
-	struct device_node *remote;
+	struct device_node *local, *remote;
 
 	if (!panel && !bridge)
 		return -EINVAL;
 	if (panel)
 		*panel = NULL;
 
+	/*
+	 * of_graph_get_remote_node() produces a noisy error message if port
+	 * node isn't found and the absence of the port is a legit case here,
+	 * so at first we silently check presence of the local port.
+	 */
+	local = of_graph_get_local_port(np);
+	if (!local)
+		return -ENODEV;
+
+	of_node_put(local);
+
 	remote = of_graph_get_remote_node(np, port, endpoint);
 	if (!remote)
 		return -ENODEV;
-- 
2.26.0

[PATCH v7 3/6] drm/tegra: output: Don't leak OF node on error

[Dmitry Osipenko]

The OF node should be put before returning error in tegra_output_probe(),
otherwise node's refcount will be leaked.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/gpu/drm/tegra/output.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/tegra/output.c b/drivers/gpu/drm/tegra/output.c
index e36e5e7c2f69..a6a711d54e88 100644
--- a/drivers/gpu/drm/tegra/output.c
+++ b/drivers/gpu/drm/tegra/output.c
@@ -102,10 +102,10 @@ int tegra_output_probe(struct tegra_output *output)
 	panel = of_parse_phandle(output->of_node, "nvidia,panel", 0);
 	if (panel) {
 		output->panel = of_drm_find_panel(panel);
+		of_node_put(panel);
+
 		if (IS_ERR(output->panel))
 			return PTR_ERR(output->panel);
-
-		of_node_put(panel);
 	}
 
 	output->edid = of_get_property(output->of_node, "nvidia,edid", &size);
@@ -113,13 +113,12 @@ int tegra_output_probe(struct tegra_output *output)
 	ddc = of_parse_phandle(output->of_node, "nvidia,ddc-i2c-bus", 0);
 	if (ddc) {
 		output->ddc = of_find_i2c_adapter_by_node(ddc);
+		of_node_put(ddc);
+
 		if (!output->ddc) {
 			err = -EPROBE_DEFER;
-			of_node_put(ddc);
 			return err;
 		}
-
-		of_node_put(ddc);
 	}
 
 	output->hpd_gpio = devm_gpiod_get_from_of_node(output->dev,
-- 
2.26.0

[PATCH v7 4/6] drm/tegra: output: Support DRM bridges

[Dmitry Osipenko]

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

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/gpu/drm/tegra/drm.h    |  2 ++
 drivers/gpu/drm/tegra/output.c | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
index b25443255be6..f38de08e0c95 100644
--- a/drivers/gpu/drm/tegra/drm.h
+++ b/drivers/gpu/drm/tegra/drm.h
@@ -12,6 +12,7 @@
 #include <linux/gpio/consumer.h>
 
 #include <drm/drm_atomic.h>
+#include <drm/drm_bridge.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_encoder.h>
 #include <drm/drm_fb_helper.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 a6a711d54e88..ccd1421f1b24 100644
--- a/drivers/gpu/drm/tegra/output.c
+++ b/drivers/gpu/drm/tegra/output.c
@@ -5,6 +5,7 @@
  */
 
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_of.h>
 #include <drm/drm_panel.h>
 #include <drm/drm_simple_kms_helper.h>
 
@@ -99,8 +100,19 @@ int tegra_output_probe(struct tegra_output *output)
 	if (!output->of_node)
 		output->of_node = output->dev->of_node;
 
+	err = drm_of_find_panel_or_bridge(output->of_node, -1, -1,
+					  &output->panel, &output->bridge);
+	if (err && err != -ENODEV)
+		return err;
+
 	panel = of_parse_phandle(output->of_node, "nvidia,panel", 0);
 	if (panel) {
+		/*
+		 * Don't mix nvidia,panel phandle with the graph in a
+		 * device-tree.
+		 */
+		WARN_ON(output->panel || output->bridge);
+
 		output->panel = of_drm_find_panel(panel);
 		of_node_put(panel);
 
-- 
2.26.0

[PATCH v7 5/6] drm/tegra: output: rgb: Support LVDS encoder bridge

[Dmitry Osipenko]

Newer Tegra device-trees will specify a video output graph, which involves
LVDS encoder bridge. This patch adds support for the LVDS encoder bridge
to the RGB output, allowing us to model the display hardware properly.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/gpu/drm/tegra/rgb.c | 58 +++++++++++++++++++++++++++++++------
 1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c
index 0562a7eb793f..9a7024ec96bc 100644
--- a/drivers/gpu/drm/tegra/rgb.c
+++ b/drivers/gpu/drm/tegra/rgb.c
@@ -7,6 +7,7 @@
 #include <linux/clk.h>
 
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge_connector.h>
 #include <drm/drm_panel.h>
 #include <drm/drm_simple_kms_helper.h>
 
@@ -267,24 +268,63 @@ int tegra_dc_rgb_remove(struct tegra_dc *dc)
 int tegra_dc_rgb_init(struct drm_device *drm, struct tegra_dc *dc)
 {
 	struct tegra_output *output = dc->rgb;
+	struct drm_connector *connector;
 	int err;
 
 	if (!dc->rgb)
 		return -ENODEV;
 
-	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_simple_encoder_init(drm, &output->encoder, DRM_MODE_ENCODER_LVDS);
 	drm_encoder_helper_add(&output->encoder,
 			       &tegra_rgb_encoder_helper_funcs);
 
-	drm_connector_attach_encoder(&output->connector,
-					  &output->encoder);
-	drm_connector_register(&output->connector);
+	/*
+	 * Tegra devices that have LVDS panel utilize LVDS encoder bridge
+	 * for converting up to 28 LCD LVTTL lanes into 5/4 LVDS lanes that
+	 * go to display panel's receiver.
+	 *
+	 * Encoder usually have a power-down control which needs to be enabled
+	 * in order to transmit data to the panel.  Historically devices that
+	 * use an older device-tree version didn't model the bridge, assuming
+	 * that encoder is turned ON by default, while today's DRM allows us
+	 * to model LVDS encoder properly.
+	 *
+	 * Newer device-trees utilize LVDS encoder bridge, which provides
+	 * us with a connector and handles the display panel.
+	 *
+	 * For older device-trees we fall back to our own connector and use
+	 * nvidia,panel phandle.
+	 */
+	if (output->bridge) {
+		err = drm_bridge_attach(&output->encoder, output->bridge,
+					NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+		if (err) {
+			dev_err(output->dev, "failed to attach bridge: %d\n",
+				err);
+			return err;
+		}
+
+		connector = drm_bridge_connector_init(drm, &output->encoder);
+		if (IS_ERR(connector)) {
+			dev_err(output->dev,
+				"failed to initialize bridge connector: %pe\n",
+				connector);
+			return PTR_ERR(connector);
+		}
+
+		drm_connector_attach_encoder(connector, &output->encoder);
+	} else {
+		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_connector_attach_encoder(&output->connector,
+					     &output->encoder);
+		drm_connector_register(&output->connector);
+	}
 
 	err = tegra_output_init(drm, output);
 	if (err < 0) {
-- 
2.26.0

[PATCH v7 6/6] drm/tegra: output: rgb: Wrap directly-connected panel into DRM bridge

[Dmitry Osipenko]

Currently Tegra DRM driver manually manages display panel, but this
management could be moved out into DRM core if we'll wrap panel into
DRM bridge. This patch wraps RGB panel into a DRM bridge and removes
manual handling of the panel from the RGB output code.

Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/gpu/drm/tegra/rgb.c | 70 ++++++++++---------------------------
 1 file changed, 18 insertions(+), 52 deletions(-)

diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c
index 9a7024ec96bc..4142a56ca764 100644
--- a/drivers/gpu/drm/tegra/rgb.c
+++ b/drivers/gpu/drm/tegra/rgb.c
@@ -8,7 +8,6 @@
 
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_bridge_connector.h>
-#include <drm/drm_panel.h>
 #include <drm/drm_simple_kms_helper.h>
 
 #include "drm.h"
@@ -86,45 +85,13 @@ static void tegra_dc_write_regs(struct tegra_dc *dc,
 		tegra_dc_writel(dc, table[i].value, table[i].offset);
 }
 
-static const struct drm_connector_funcs tegra_rgb_connector_funcs = {
-	.reset = drm_atomic_helper_connector_reset,
-	.detect = tegra_output_connector_detect,
-	.fill_modes = drm_helper_probe_single_connector_modes,
-	.destroy = tegra_output_connector_destroy,
-	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
-	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
-};
-
-static enum drm_mode_status
-tegra_rgb_connector_mode_valid(struct drm_connector *connector,
-			       struct drm_display_mode *mode)
-{
-	/*
-	 * FIXME: For now, always assume that the mode is okay. There are
-	 * unresolved issues with clk_round_rate(), which doesn't always
-	 * reliably report whether a frequency can be set or not.
-	 */
-	return MODE_OK;
-}
-
-static const struct drm_connector_helper_funcs tegra_rgb_connector_helper_funcs = {
-	.get_modes = tegra_output_connector_get_modes,
-	.mode_valid = tegra_rgb_connector_mode_valid,
-};
-
 static void tegra_rgb_encoder_disable(struct drm_encoder *encoder)
 {
 	struct tegra_output *output = encoder_to_output(encoder);
 	struct tegra_rgb *rgb = to_rgb(output);
 
-	if (output->panel)
-		drm_panel_disable(output->panel);
-
 	tegra_dc_write_regs(rgb->dc, rgb_disable, ARRAY_SIZE(rgb_disable));
 	tegra_dc_commit(rgb->dc);
-
-	if (output->panel)
-		drm_panel_unprepare(output->panel);
 }
 
 static void tegra_rgb_encoder_enable(struct drm_encoder *encoder)
@@ -133,9 +100,6 @@ static void tegra_rgb_encoder_enable(struct drm_encoder *encoder)
 	struct tegra_rgb *rgb = to_rgb(output);
 	u32 value;
 
-	if (output->panel)
-		drm_panel_prepare(output->panel);
-
 	tegra_dc_write_regs(rgb->dc, rgb_enable, ARRAY_SIZE(rgb_enable));
 
 	value = DE_SELECT_ACTIVE | DE_CONTROL_NORMAL;
@@ -157,9 +121,6 @@ static void tegra_rgb_encoder_enable(struct drm_encoder *encoder)
 	tegra_dc_writel(rgb->dc, value, DC_DISP_SHIFT_CLOCK_OPTIONS);
 
 	tegra_dc_commit(rgb->dc);
-
-	if (output->panel)
-		drm_panel_enable(output->panel);
 }
 
 static int
@@ -278,6 +239,23 @@ int tegra_dc_rgb_init(struct drm_device *drm, struct tegra_dc *dc)
 	drm_encoder_helper_add(&output->encoder,
 			       &tegra_rgb_encoder_helper_funcs);
 
+	/*
+	 * Wrap directly-connected panel into DRM bridge in order to let
+	 * DRM core to handle panel for us.
+	 */
+	if (output->panel) {
+		output->bridge = devm_drm_panel_bridge_add(output->dev,
+							   output->panel);
+		if (IS_ERR(output->bridge)) {
+			dev_err(output->dev,
+				"failed to wrap panel into bridge: %pe\n",
+				output->bridge);
+			return PTR_ERR(output->bridge);
+		}
+
+		output->panel = NULL;
+	}
+
 	/*
 	 * Tegra devices that have LVDS panel utilize LVDS encoder bridge
 	 * for converting up to 28 LCD LVTTL lanes into 5/4 LVDS lanes that
@@ -292,8 +270,7 @@ int tegra_dc_rgb_init(struct drm_device *drm, struct tegra_dc *dc)
 	 * Newer device-trees utilize LVDS encoder bridge, which provides
 	 * us with a connector and handles the display panel.
 	 *
-	 * For older device-trees we fall back to our own connector and use
-	 * nvidia,panel phandle.
+	 * For older device-trees we wrapped panel into the panel-bridge.
 	 */
 	if (output->bridge) {
 		err = drm_bridge_attach(&output->encoder, output->bridge,
@@ -313,17 +290,6 @@ int tegra_dc_rgb_init(struct drm_device *drm, struct tegra_dc *dc)
 		}
 
 		drm_connector_attach_encoder(connector, &output->encoder);
-	} else {
-		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_connector_attach_encoder(&output->connector,
-					     &output->encoder);
-		drm_connector_register(&output->connector);
 	}
 
 	err = tegra_output_init(drm, output);
-- 
2.26.0

Re: [PATCH v7 1/6] of_graph: add of_graph_get_local_port()

[Laurent Pinchart]

Hi Dmitry,

Thank you for the patch.

On Sun, Jun 14, 2020 at 08:22:29PM +0300, Dmitry Osipenko wrote:
> In some case, like a DRM display code for example, it's useful to silently
> check whether port node exists at all in a device-tree before proceeding
> with parsing the graph.
> 
> This patch adds of_graph_get_local_port() which returns pointer to a local
> port node, or NULL if graph isn't specified in a device-tree for a given
> device node.
> 
> Reviewed-by: Rob Herring <robh@kernel.org>
> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/of/property.c    | 32 +++++++++++++++++++++++---------
>  include/linux/of_graph.h |  7 +++++++
>  2 files changed, 30 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 1f2086f4e7ce..05c5f619b8bb 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
>  	 * parent port node.
>  	 */
>  	if (!prev) {
> -		struct device_node *node;
> -
> -		node = of_get_child_by_name(parent, "ports");
> -		if (node)
> -			parent = node;
> -
> -		port = of_get_child_by_name(parent, "port");
> -		of_node_put(node);
> -
> +		port = of_graph_get_local_port(parent);
>  		if (!port) {
>  			pr_err("graph: no port node found in %pOF\n", parent);
>  			return NULL;
> @@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
>  }
>  EXPORT_SYMBOL(of_graph_get_remote_port);
>  
> +/**
> + * of_graph_get_local_port() - get local port node
> + * @node: pointer to a local endpoint device_node
> + *
> + * Return: First local port node associated with local endpoint node linked
> + *	   to @node. Use of_node_put() on it when done.
> + */
> +struct device_node *of_graph_get_local_port(const struct device_node *node)
> +{
> +	struct device_node *ports, *port;
> +
> +	ports = of_get_child_by_name(node, "ports");
> +	if (ports)
> +		node = ports;
> +
> +	port = of_get_child_by_name(node, "port");
> +	of_node_put(ports);
> +
> +	return port;

The implementation doesn't seem to match the documentation. If node is a
pointer to an endpoint, it should not have any ports child.

> +}
> +EXPORT_SYMBOL(of_graph_get_local_port);
> +
>  int of_graph_get_endpoint_count(const struct device_node *np)
>  {
>  	struct device_node *endpoint;
> diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
> index 01038a6aade0..1fdeb72c7765 100644
> --- a/include/linux/of_graph.h
> +++ b/include/linux/of_graph.h
> @@ -54,6 +54,7 @@ struct device_node *of_graph_get_remote_port_parent(
>  struct device_node *of_graph_get_remote_port(const struct device_node *node);
>  struct device_node *of_graph_get_remote_node(const struct device_node *node,
>  					     u32 port, u32 endpoint);
> +struct device_node *of_graph_get_local_port(const struct device_node *node);
>  #else
>  
>  static inline int of_graph_parse_endpoint(const struct device_node *node,
> @@ -116,6 +117,12 @@ static inline struct device_node *of_graph_get_remote_node(
>  	return NULL;
>  }
>  
> +static inline struct device_node *of_graph_get_local_port(
> +					const struct device_node *node)
> +{
> +	return NULL;
> +}
> +
>  #endif /* CONFIG_OF */
>  
>  #endif /* __LINUX_OF_GRAPH_H */
> -- 
> 2.26.0
> 

-- 
Regards,

Laurent Pinchart

Re: [PATCH v7 1/6] of_graph: add of_graph_get_local_port()

[Laurent Pinchart]

On Tue, Jun 16, 2020 at 04:21:12AM +0300, Laurent Pinchart wrote:
> Hi Dmitry,
> 
> Thank you for the patch.
> 
> On Sun, Jun 14, 2020 at 08:22:29PM +0300, Dmitry Osipenko wrote:
> > In some case, like a DRM display code for example, it's useful to silently
> > check whether port node exists at all in a device-tree before proceeding
> > with parsing the graph.
> > 
> > This patch adds of_graph_get_local_port() which returns pointer to a local
> > port node, or NULL if graph isn't specified in a device-tree for a given
> > device node.
> > 
> > Reviewed-by: Rob Herring <robh@kernel.org>
> > Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> > Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> > ---
> >  drivers/of/property.c    | 32 +++++++++++++++++++++++---------
> >  include/linux/of_graph.h |  7 +++++++
> >  2 files changed, 30 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/of/property.c b/drivers/of/property.c
> > index 1f2086f4e7ce..05c5f619b8bb 100644
> > --- a/drivers/of/property.c
> > +++ b/drivers/of/property.c
> > @@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
> >  	 * parent port node.
> >  	 */
> >  	if (!prev) {
> > -		struct device_node *node;
> > -
> > -		node = of_get_child_by_name(parent, "ports");
> > -		if (node)
> > -			parent = node;
> > -
> > -		port = of_get_child_by_name(parent, "port");
> > -		of_node_put(node);
> > -
> > +		port = of_graph_get_local_port(parent);
> >  		if (!port) {
> >  			pr_err("graph: no port node found in %pOF\n", parent);
> >  			return NULL;
> > @@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
> >  }
> >  EXPORT_SYMBOL(of_graph_get_remote_port);
> >  
> > +/**
> > + * of_graph_get_local_port() - get local port node
> > + * @node: pointer to a local endpoint device_node
> > + *
> > + * Return: First local port node associated with local endpoint node linked
> > + *	   to @node. Use of_node_put() on it when done.
> > + */
> > +struct device_node *of_graph_get_local_port(const struct device_node *node)

I forgot to mention that, given that there could be multiple 'port'
nodes, this function would be better named
of_graph_get_first_local_port(). 'first' here would refer to the nodes
order in the device tree, which I believe may not match the port number.
For instance, in the following case

	ports {
		#address-cells = <1>;
		#size-cells = <1>;
		port@1 {
			reg = <1>;
		};
		port@0 {
			reg = <0>;
		};
	};

the function would I believe return port@1. It may be a good idea to
explain this in the documentation. Depending on how you use this
function, if your only use case is to test for the presence of port
nodes, it may be best to return a bool and name it of_graph_has_port()
or something similar.

> > +{
> > +	struct device_node *ports, *port;
> > +
> > +	ports = of_get_child_by_name(node, "ports");
> > +	if (ports)
> > +		node = ports;
> > +
> > +	port = of_get_child_by_name(node, "port");
> > +	of_node_put(ports);
> > +
> > +	return port;
> 
> The implementation doesn't seem to match the documentation. If node is a
> pointer to an endpoint, it should not have any ports child.
> 
> > +}
> > +EXPORT_SYMBOL(of_graph_get_local_port);
> > +
> >  int of_graph_get_endpoint_count(const struct device_node *np)
> >  {
> >  	struct device_node *endpoint;
> > diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
> > index 01038a6aade0..1fdeb72c7765 100644
> > --- a/include/linux/of_graph.h
> > +++ b/include/linux/of_graph.h
> > @@ -54,6 +54,7 @@ struct device_node *of_graph_get_remote_port_parent(
> >  struct device_node *of_graph_get_remote_port(const struct device_node *node);
> >  struct device_node *of_graph_get_remote_node(const struct device_node *node,
> >  					     u32 port, u32 endpoint);
> > +struct device_node *of_graph_get_local_port(const struct device_node *node);
> >  #else
> >  
> >  static inline int of_graph_parse_endpoint(const struct device_node *node,
> > @@ -116,6 +117,12 @@ static inline struct device_node *of_graph_get_remote_node(
> >  	return NULL;
> >  }
> >  
> > +static inline struct device_node *of_graph_get_local_port(
> > +					const struct device_node *node)
> > +{
> > +	return NULL;
> > +}
> > +
> >  #endif /* CONFIG_OF */
> >  
> >  #endif /* __LINUX_OF_GRAPH_H */

-- 
Regards,

Laurent Pinchart

Re: [PATCH v7 2/6] drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

[Laurent Pinchart]

Hi Dmitry,

Thank you for the patch.

On Sun, Jun 14, 2020 at 08:22:30PM +0300, Dmitry Osipenko wrote:
> When graph isn't defined in a device-tree, the of_graph_get_remote_node()
> prints a noisy error message, telling that port node is not found. This is
> undesirable behaviour in our case because absence of a panel/bridge graph
> is a valid case. Let's check presence of the local port in a device-tree
> before proceeding with parsing the graph.
> 
> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/gpu/drm/drm_of.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index b50b44e76279..e0652c38f357 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -239,13 +239,24 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>  				struct drm_bridge **bridge)
>  {
>  	int ret = -EPROBE_DEFER;
> -	struct device_node *remote;
> +	struct device_node *local, *remote;
>  
>  	if (!panel && !bridge)
>  		return -EINVAL;
>  	if (panel)
>  		*panel = NULL;
>  
> +	/*
> +	 * of_graph_get_remote_node() produces a noisy error message if port
> +	 * node isn't found and the absence of the port is a legit case here,
> +	 * so at first we silently check presence of the local port.
> +	 */
> +	local = of_graph_get_local_port(np);
> +	if (!local)
> +		return -ENODEV;
> +
> +	of_node_put(local);
> +

The code looks fine, but you may want to take into account my proposal
in 1/7 to instead create a of_graph_has_port() function. The could would
be simpler here.

>  	remote = of_graph_get_remote_node(np, port, endpoint);
>  	if (!remote)
>  		return -ENODEV;

-- 
Regards,

Laurent Pinchart

Re: [PATCH v7 1/6] of_graph: add of_graph_get_local_port()

[Dmitry Osipenko]

16.06.2020 04:25, Laurent Pinchart пишет:
> On Tue, Jun 16, 2020 at 04:21:12AM +0300, Laurent Pinchart wrote:
>> Hi Dmitry,
>>
>> Thank you for the patch.
>>
>> On Sun, Jun 14, 2020 at 08:22:29PM +0300, Dmitry Osipenko wrote:
>>> In some case, like a DRM display code for example, it's useful to silently
>>> check whether port node exists at all in a device-tree before proceeding
>>> with parsing the graph.
>>>
>>> This patch adds of_graph_get_local_port() which returns pointer to a local
>>> port node, or NULL if graph isn't specified in a device-tree for a given
>>> device node.
>>>
>>> Reviewed-by: Rob Herring <robh@kernel.org>
>>> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>> ---
>>>  drivers/of/property.c    | 32 +++++++++++++++++++++++---------
>>>  include/linux/of_graph.h |  7 +++++++
>>>  2 files changed, 30 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/of/property.c b/drivers/of/property.c
>>> index 1f2086f4e7ce..05c5f619b8bb 100644
>>> --- a/drivers/of/property.c
>>> +++ b/drivers/of/property.c
>>> @@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
>>>  	 * parent port node.
>>>  	 */
>>>  	if (!prev) {
>>> -		struct device_node *node;
>>> -
>>> -		node = of_get_child_by_name(parent, "ports");
>>> -		if (node)
>>> -			parent = node;
>>> -
>>> -		port = of_get_child_by_name(parent, "port");
>>> -		of_node_put(node);
>>> -
>>> +		port = of_graph_get_local_port(parent);
>>>  		if (!port) {
>>>  			pr_err("graph: no port node found in %pOF\n", parent);
>>>  			return NULL;
>>> @@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
>>>  }
>>>  EXPORT_SYMBOL(of_graph_get_remote_port);
>>>  
>>> +/**
>>> + * of_graph_get_local_port() - get local port node
>>> + * @node: pointer to a local endpoint device_node
>>> + *
>>> + * Return: First local port node associated with local endpoint node linked
>>> + *	   to @node. Use of_node_put() on it when done.
>>> + */
>>> +struct device_node *of_graph_get_local_port(const struct device_node *node)
> 
> I forgot to mention that, given that there could be multiple 'port'
> nodes, this function would be better named
> of_graph_get_first_local_port(). 'first' here would refer to the nodes
> order in the device tree, which I believe may not match the port number.
> For instance, in the following case
> 
> 	ports {
> 		#address-cells = <1>;
> 		#size-cells = <1>;
> 		port@1 {
> 			reg = <1>;
> 		};
> 		port@0 {
> 			reg = <0>;
> 		};
> 	};
> 
> the function would I believe return port@1. It may be a good idea to
> explain this in the documentation.

Hello Laurent,

It's correct that the port@1 will be returned in yours example.

I'll improve the doc and the function's name in the next revision, thank
you for the suggestions!

> Depending on how you use this
> function, if your only use case is to test for the presence of port
> nodes, it may be best to return a bool and name it of_graph_has_port()
> or something similar.
> 
>>> +{
>>> +	struct device_node *ports, *port;
>>> +
>>> +	ports = of_get_child_by_name(node, "ports");
>>> +	if (ports)
>>> +		node = ports;
>>> +
>>> +	port = of_get_child_by_name(node, "port");
>>> +	of_node_put(ports);
>>> +
>>> +	return port;
>>
>> The implementation doesn't seem to match the documentation. If node is a
>> pointer to an endpoint, it should not have any ports child.

Right, I'll reword the doc in v8. This function doesn't differentiate
between start / end points. It's up to a user of this function to check
whether node is endpoint or something else if needed.

Thank you very much for the comments!

Re: [PATCH v7 1/6] of_graph: add of_graph_get_local_port()

[Dmitry Osipenko]

16.06.2020 16:56, Dmitry Osipenko пишет:
> 16.06.2020 04:25, Laurent Pinchart пишет:
>> On Tue, Jun 16, 2020 at 04:21:12AM +0300, Laurent Pinchart wrote:
>>> Hi Dmitry,
>>>
>>> Thank you for the patch.
>>>
>>> On Sun, Jun 14, 2020 at 08:22:29PM +0300, Dmitry Osipenko wrote:
>>>> In some case, like a DRM display code for example, it's useful to silently
>>>> check whether port node exists at all in a device-tree before proceeding
>>>> with parsing the graph.
>>>>
>>>> This patch adds of_graph_get_local_port() which returns pointer to a local
>>>> port node, or NULL if graph isn't specified in a device-tree for a given
>>>> device node.
>>>>
>>>> Reviewed-by: Rob Herring <robh@kernel.org>
>>>> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
>>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>>> ---
>>>>  drivers/of/property.c    | 32 +++++++++++++++++++++++---------
>>>>  include/linux/of_graph.h |  7 +++++++
>>>>  2 files changed, 30 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/drivers/of/property.c b/drivers/of/property.c
>>>> index 1f2086f4e7ce..05c5f619b8bb 100644
>>>> --- a/drivers/of/property.c
>>>> +++ b/drivers/of/property.c
>>>> @@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
>>>>  	 * parent port node.
>>>>  	 */
>>>>  	if (!prev) {
>>>> -		struct device_node *node;
>>>> -
>>>> -		node = of_get_child_by_name(parent, "ports");
>>>> -		if (node)
>>>> -			parent = node;
>>>> -
>>>> -		port = of_get_child_by_name(parent, "port");
>>>> -		of_node_put(node);
>>>> -
>>>> +		port = of_graph_get_local_port(parent);
>>>>  		if (!port) {
>>>>  			pr_err("graph: no port node found in %pOF\n", parent);
>>>>  			return NULL;
>>>> @@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
>>>>  }
>>>>  EXPORT_SYMBOL(of_graph_get_remote_port);
>>>>  
>>>> +/**
>>>> + * of_graph_get_local_port() - get local port node
>>>> + * @node: pointer to a local endpoint device_node
>>>> + *
>>>> + * Return: First local port node associated with local endpoint node linked
>>>> + *	   to @node. Use of_node_put() on it when done.
>>>> + */
>>>> +struct device_node *of_graph_get_local_port(const struct device_node *node)
>>
>> I forgot to mention that, given that there could be multiple 'port'
>> nodes, this function would be better named
>> of_graph_get_first_local_port(). 'first' here would refer to the nodes
>> order in the device tree, which I believe may not match the port number.
>> For instance, in the following case
>>
>> 	ports {
>> 		#address-cells = <1>;
>> 		#size-cells = <1>;
>> 		port@1 {
>> 			reg = <1>;
>> 		};
>> 		port@0 {
>> 			reg = <0>;
>> 		};
>> 	};
>>
>> the function would I believe return port@1. It may be a good idea to
>> explain this in the documentation.
> 
> Hello Laurent,
> 
> It's correct that the port@1 will be returned in yours example.
> 
> I'll improve the doc and the function's name in the next revision, thank
> you for the suggestions!
> 
>> Depending on how you use this
>> function, if your only use case is to test for the presence of port
>> nodes, it may be best to return a bool and name it of_graph_has_port()
>> or something similar.
>>
>>>> +{
>>>> +	struct device_node *ports, *port;
>>>> +
>>>> +	ports = of_get_child_by_name(node, "ports");
>>>> +	if (ports)
>>>> +		node = ports;
>>>> +
>>>> +	port = of_get_child_by_name(node, "port");
>>>> +	of_node_put(ports);
>>>> +
>>>> +	return port;
>>>
>>> The implementation doesn't seem to match the documentation. If node is a
>>> pointer to an endpoint, it should not have any ports child.
> 
> Right, I'll reword the doc in v8. This function doesn't differentiate
> between start / end points. It's up to a user of this function to check
> whether node is endpoint or something else if needed.
> 
> Thank you very much for the comments!
> 

Although, I re-read the doc comment and compared it to the wording of
the other of_graph_*() functions and it's already good as-is to me
because the doc explicitly says the "Return: First local port associated
with local endpoint...", which is exactly what this function does.

But still the function name and it's brief description could be improved.

Re: [PATCH v7 2/6] drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

[Dmitry Osipenko]

16.06.2020 04:26, Laurent Pinchart пишет:
> Hi Dmitry,
> 
> Thank you for the patch.
> 
> On Sun, Jun 14, 2020 at 08:22:30PM +0300, Dmitry Osipenko wrote:
>> When graph isn't defined in a device-tree, the of_graph_get_remote_node()
>> prints a noisy error message, telling that port node is not found. This is
>> undesirable behaviour in our case because absence of a panel/bridge graph
>> is a valid case. Let's check presence of the local port in a device-tree
>> before proceeding with parsing the graph.
>>
>> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>  drivers/gpu/drm/drm_of.c | 13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>> index b50b44e76279..e0652c38f357 100644
>> --- a/drivers/gpu/drm/drm_of.c
>> +++ b/drivers/gpu/drm/drm_of.c
>> @@ -239,13 +239,24 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>  				struct drm_bridge **bridge)
>>  {
>>  	int ret = -EPROBE_DEFER;
>> -	struct device_node *remote;
>> +	struct device_node *local, *remote;
>>  
>>  	if (!panel && !bridge)
>>  		return -EINVAL;
>>  	if (panel)
>>  		*panel = NULL;
>>  
>> +	/*
>> +	 * of_graph_get_remote_node() produces a noisy error message if port
>> +	 * node isn't found and the absence of the port is a legit case here,
>> +	 * so at first we silently check presence of the local port.
>> +	 */
>> +	local = of_graph_get_local_port(np);
>> +	if (!local)
>> +		return -ENODEV;
>> +
>> +	of_node_put(local);
>> +
> 
> The code looks fine, but you may want to take into account my proposal
> in 1/7 to instead create a of_graph_has_port() function. The could would
> be simpler here.
> 
>>  	remote = of_graph_get_remote_node(np, port, endpoint);
>>  	if (!remote)
>>  		return -ENODEV;
> 

I like yours proposals and will prepare v8 based on them, thanks!