diff mbox series

[v9,45/61] drm/bridge: lontium-lt9611: Advertise HDMI 1.4 capabilities

Message ID 20260723-dw-hdmi-qp-scramb-v9-45-4fb12ea22ac9@collabora.com (mailing list archive)
State New
Headers
Series Add HDMI 2.0 support to DW HDMI QP TX |

Commit Message

Cristian Ciocaltea July 23, 2026, 1:35 a.m. UTC 
Bridges using DRM_BRIDGE_OP_HDMI are expected to provide the supported
HDMI version.  This is not enforced yet, but will become mandatory once
the migration to the caps-based HDMI connector initialization API is
complete.

As LT9611 supposedly cannot drive a TMDS character rate exceeding 297
MHz, advertise HDMI 1.4 as the supported version.  HDMI 1.4 allows up to
340 MHz, so set the bridge's max_tmds_char_rate to ensure the connector
limit derived from supported_hdmi_ver remains within the hardware
capabilities.

drm_bridge_connector_atomic_check() calls
drm_atomic_helper_connector_hdmi_check(), which rejects modes whose
computed TMDS character rate exceeds the connector's max_tmds_char_rate
before invoking the driver's .tmds_char_rate_valid hook.  Since
max_tmds_char_rate now carries the existing effective limit,
lt9611_hdmi_tmds_char_rate_valid() is redundant.  Drop it.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
 drivers/gpu/drm/bridge/lontium-lt9611.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

Comments

sashiko-bot@kernel.org July 23, 2026, 2 a.m. UTC | #1 
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Calling sleeping function msleep() from atomic context in lt9611_bridge_atomic_enable
--

--- Patch [45]: [PATCH v9 45/61] drm/bridge: lontium-lt9611: Advertise HDMI 1.4 capabilities ---
commit 68a26d2eb02093b29ceceec99268ce3f7d8ba524
Author: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>

drm/bridge: lontium-lt9611: Advertise HDMI 1.4 capabilities

This commit adds HDMI 1.4 capability advertisement to the lontium-lt9611 bridge.
It sets the supported version and maximum TMDS character rate.
It also removes the redundant lt9611_hdmi_tmds_char_rate_valid function.

> diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
> index b6a368f712853..19971ffade8ba 100644
> --- a/drivers/gpu/drm/bridge/lontium-lt9611.c
> +++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
[ ... ]
> @@ -1029,7 +1018,6 @@ static const struct drm_bridge_funcs lt9611_bridge_funcs = {
>  	.atomic_create_state = drm_atomic_helper_bridge_create_state,
>  	.atomic_get_input_bus_fmts = lt9611_atomic_get_input_bus_fmts,
>  
> -	.hdmi_tmds_char_rate_valid = lt9611_hdmi_tmds_char_rate_valid,
>  	.hdmi_write_audio_infoframe = lt9611_hdmi_write_audio_infoframe,
>  	.hdmi_clear_audio_infoframe = lt9611_hdmi_clear_audio_infoframe,

[Severity: High]
This is a pre-existing issue, but since we are modifying the bridge
capabilities here, I noticed a potential sleeping in atomic context issue
in the existing lt9611_bridge_atomic_enable function:

drivers/gpu/drm/bridge/lontium-lt9611.c:lt9611_bridge_atomic_enable() {
	...
	lt9611_hdmi_tx_digital(lt9611, connector->display_info.is_hdmi);
	lt9611_hdmi_tx_phy(lt9611);

	msleep(500);

	lt9611_video_check(lt9611);
	...
}

Is it safe to use msleep in this path?

DRM bridge atomic enable callbacks run in an atomic context during non-blocking
commits where sleeping is forbidden. Does this msleep cause scheduling while
atomic warnings or potential lockups when triggered via display mode setting or
hotplug events?
diff mbox series

Patch

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
index b6a368f71285..19971ffade8b 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -5,6 +5,7 @@ 
  */
 
 #include <linux/gpio/consumer.h>
+#include <linux/hdmi.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/media-bus-format.h>
@@ -952,18 +953,6 @@  static int lt9611_hdmi_write_hdmi_infoframe(struct drm_bridge *bridge,
 	return 0;
 }
 
-static enum drm_mode_status
-lt9611_hdmi_tmds_char_rate_valid(const struct drm_bridge *bridge,
-				 const struct drm_display_mode *mode,
-				 unsigned long long tmds_rate)
-{
-	/* 297 MHz for 4k@30 mode */
-	if (tmds_rate > 297000000)
-		return MODE_CLOCK_HIGH;
-
-	return MODE_OK;
-}
-
 static int lt9611_hdmi_audio_startup(struct drm_bridge *bridge,
 				     struct drm_connector *connector)
 {
@@ -1029,7 +1018,6 @@  static const struct drm_bridge_funcs lt9611_bridge_funcs = {
 	.atomic_create_state = drm_atomic_helper_bridge_create_state,
 	.atomic_get_input_bus_fmts = lt9611_atomic_get_input_bus_fmts,
 
-	.hdmi_tmds_char_rate_valid = lt9611_hdmi_tmds_char_rate_valid,
 	.hdmi_write_audio_infoframe = lt9611_hdmi_write_audio_infoframe,
 	.hdmi_clear_audio_infoframe = lt9611_hdmi_clear_audio_infoframe,
 	.hdmi_write_avi_infoframe = lt9611_hdmi_write_avi_infoframe,
@@ -1177,6 +1165,8 @@  static int lt9611_probe(struct i2c_client *client)
 	lt9611->bridge.hdmi_audio_dev = dev;
 	lt9611->bridge.hdmi_audio_max_i2s_playback_channels = 8;
 	lt9611->bridge.hdmi_audio_dai_port = 2;
+	lt9611->bridge.supported_hdmi_ver = HDMI_VERSION_1_4;
+	lt9611->bridge.max_tmds_char_rate = 297000000; /* 297 MHz for 4k@30 mode */
 
 	drm_bridge_add(&lt9611->bridge);