Re: [PATCH 5/5] drm/bridge: simple-bridge: Add next panel support

Liu Ying
2025-03-06T06:16:04Z

On 03/04/2025, Maxime Ripard wrote:
> On Tue, Mar 04, 2025 at 06:15:30PM +0800, Liu Ying wrote:
>> The next bridge connected to a simple bridge could be a panel, e.g.,
>> a DPI panel connected to a DPI color encoder. Add the next panel support,
>> instead of supporting non-panel next bridge only.
>>
>> Signed-off-by: Liu Ying <victor.liu@nxp.com>
>> ---
>> drivers/gpu/drm/bridge/Kconfig | 1 +
>> drivers/gpu/drm/bridge/simple-bridge.c | 32 ++++++++++++++++----------
>> 2 files changed, 21 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
>> index d20f1646dac2..92187dbdd32b 100644
>> --- a/drivers/gpu/drm/bridge/Kconfig
>> +++ b/drivers/gpu/drm/bridge/Kconfig
>> @@ -310,6 +310,7 @@ config DRM_SIMPLE_BRIDGE
>> tristate "Simple DRM bridge support"
>> depends on OF
>> select DRM_KMS_HELPER
>> + select DRM_PANEL_BRIDGE
>> help
>> Support for non-programmable DRM bridges, such as ADI ADV7123, TI
>> THS8134 and THS8135 or passive resistor ladder DACs.
>> diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
>> index c0445bd20e07..4c585e5583ca 100644
>> --- a/drivers/gpu/drm/bridge/simple-bridge.c
>> +++ b/drivers/gpu/drm/bridge/simple-bridge.c
>> @@ -19,6 +19,7 @@
>> #include <drm/drm_crtc.h>
>> #include <drm/drm_edid.h>
>> #include <drm/drm_of.h>
>> +#include <drm/drm_panel.h>
>> #include <drm/drm_print.h>
>> #include <drm/drm_probe_helper.h>
>>
>> @@ -35,6 +36,7 @@ struct simple_bridge {
>> const struct simple_bridge_info *info;
>>
>> struct drm_bridge *next_bridge;
>> + struct drm_panel *next_panel;
>> struct regulator *vdd;
>> struct gpio_desc *enable;
>>
>> @@ -114,6 +116,10 @@ static int simple_bridge_attach(struct drm_bridge *bridge,
>> struct simple_bridge *sbridge = drm_bridge_to_simple_bridge(bridge);
>> int ret;
>>
>> + if (sbridge->next_panel)
>> + return drm_bridge_attach(bridge->encoder, sbridge->next_bridge,
>> + bridge, flags);
>> +
>> ret = drm_bridge_attach(bridge->encoder, sbridge->next_bridge, bridge,
>> DRM_BRIDGE_ATTACH_NO_CONNECTOR);
>> if (ret < 0)
>> @@ -247,7 +253,6 @@ static int simple_bridge_get_dpi_color_coding(struct simple_bridge *sbridge,
>> static int simple_bridge_probe(struct platform_device *pdev)
>> {
>> struct simple_bridge *sbridge;
>> - struct device_node *remote;
>> int ret;
>>
>> sbridge = devm_kzalloc(&pdev->dev, sizeof(*sbridge), GFP_KERNEL);
>> @@ -257,17 +262,20 @@ static int simple_bridge_probe(struct platform_device *pdev)
>> sbridge->info = of_device_get_match_data(&pdev->dev);
>>
>> /* Get the next bridge in the pipeline. */
>> - remote = of_graph_get_remote_node(pdev->dev.of_node, 1, -1);
>> - if (!remote)
>> - return -EINVAL;
>> -
>> - sbridge->next_bridge = of_drm_find_bridge(remote);
>> - of_node_put(remote);
>> -
>> - if (!sbridge->next_bridge) {
>> - dev_dbg(&pdev->dev, "Next bridge not found, deferring probe\n");
>> - return -EPROBE_DEFER;
>> - }
>> + ret = drm_of_find_panel_or_bridge(pdev->dev.of_node, 1, -1,
>> + &sbridge->next_panel,
>> + &sbridge->next_bridge);
>> + if (ret)
>> + return dev_err_probe(&pdev->dev, ret,
>> + "Next panel or bridge not found\n");
>> +
>> + if (sbridge->next_panel)
>> + sbridge->next_bridge = devm_drm_panel_bridge_add(&pdev->dev,
>> + sbridge->next_panel);
>> +
>> + if (IS_ERR(sbridge->next_bridge))
>> + return dev_err_probe(&pdev->dev, PTR_ERR(sbridge->next_bridge),
>> + "Next bridge not found\n");
>
> This makes sense in general, but I think a better approach would be to
> use devm/drmm_of_get_bridge here.

I chose to open-code devm_of_get_bridge() because sbridge->next_panel can
be grabbed and used to determine the logics in simple_bridge_attach() and
the flags handled over to drm_bridge_attach().

However, if a separate driver is needed for the DPI color encoder, I won't
touch this driver.

>
> Maxime

--
Regards,
Liu Ying