Hi Marek,
On 9/4/2025 9:27 PM, Marek Szyprowski wrote:
On 04.09.2025 05:19, Damon Ding wrote:
On 9/1/2025 6:25 PM, Marek Szyprowski wrote:
On 01.09.2025 05:41, Damon Ding wrote:
On 8/29/2025 4:23 PM, Marek Szyprowski wrote:
On 29.08.2025 10:08, Damon Ding wrote:
On 8/20/2025 5:20 AM, Marek Szyprowski wrote:
On 15.08.2025 04:59, Damon Ding wrote:
On 2025/8/15 5:16, Marek Szyprowski wrote:
On 14.08.2025 16:33, Marek Szyprowski wrote:
On 14.08.2025 12:47, Damon Ding wrote:
PATCH 1 is a small format optimization for struct
analogid_dp_device.
PATCH 2 is to perform mode setting in
&drm_bridge_funcs.atomic_enable.
PATCH 3-6 are preparations for apply drm_bridge_connector
helper.
PATCH 7 is to apply the drm_bridge_connector helper.
PATCH 8-10 are to move the panel/bridge parsing to the Analogix
side.
PATCH 11-12 are preparations for apply panel_bridge helper.
PATCH 13 is to apply the panel_bridge helper.
...
Could you please provide the related DTS file for the test? I will
also try to find out the reason for this unexpected issue. ;-)
Unfortunately I didn't find enough time to debug this further. The
above
log is from Samsung Snow Chromebook,
arch/arm/boot/dts/samsung/exynos5250-snow.dts
I compare the differences in the following display path before and
after this patch series:
exynos_dp -> nxp-ptn3460 -> panel "auo,b116xw03"
The issue is likely caused by the &drm_connector_funcs.detect()
related logic. Before this patch series, the nxp-ptn3460 connector is
always connector_status_connected because there is not available
&drm_connector_funcs.detect(). After it, the DRM_BRIDGE_OP_DETECT flag
make the connection status depend on analogix_dp_bridge_detect().
Could you please add the following patches additionally and try again?
(Not the final solution, just validation)
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index a93ff8f0a468..355911c47354 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1491,9 +1491,11 @@ int analogix_dp_bind(struct analogix_dp_device
*dp, struct drm_device *drm_dev)
}
}
- bridge->ops = DRM_BRIDGE_OP_DETECT |
- DRM_BRIDGE_OP_EDID |
+ bridge->ops = DRM_BRIDGE_OP_EDID |
DRM_BRIDGE_OP_MODES;
+ if (drm_bridge_is_panel(dp->plat_data->next_bridge))
+ bridge->ops |= DRM_BRIDGE_OP_DETECT;
+
bridge->of_node = dp->dev->of_node;
bridge->type = DRM_MODE_CONNECTOR_eDP;
ret = devm_drm_bridge_add(dp->dev, &dp->bridge);
It is better. Now the display panel is detected and reported to
userspace, but it looks that something is not properly initialized,
because there is garbage instead of the proper picture.
I simulated the display path mentioned above on my RK3588S EVB1 Board.
To my slight surprise, it displayed normally with the reported
connector type DRM_MODE_CONNECTOR_LVDS. ;-)
The modifications included:
1.Synchronized the Analogix DP ralated DT configurations with Samsung
Snow Chromebook.
2.Skipped the I2C transfers and GPIO operations in nxp-ptn3460 driver.
3.Set the EDID to that of eDP Panel LP079QX1-SP0V forcibly.
Additionally, I added debug logs to verify whether the functions in
ptn3460_bridge_funcs were actually called.
Did you encounter any unexpected logs during your investigation? I'd
like to perform additional tests on this issue. :-)
Okay, I've finally went to the office and tested manually all 3
Chromebook boards witch use exynos-dp based display hardware. Previously
I only did the remote tests and observed result on a webcam, which was
not directed directly at the tested displays, so I only saw the glare
from the display panel.
The results are as follows:
1. Snow (arch/arm/boot/dts/samsung/exynos5250-snow.dts) - exynos-dp ->
nxp-ptn3460 1366x768 lvds panel - works fine with the above mentioned
change.
2. Peach-Pit (arch/arm/boot/dts/samsung/exynos5420-peach-pit.dts) -
exynos-dp -> parade,ps8625 -> auo,b116xw03 1366x768 lvds panel -
displays garbage, this was the only board I previously was able to see
partially on the webcam.
3. Peach-Pi (arch/arm/boot/dts/samsung/exynos5800-peach-pi.dts) -
exynos-dp -> auo,b133htn01 1920x1080 edp panel - also displays garbage.
Then I found why both Peach boards displays garbage on boot - the
framebuffer emulation is initialized for 1024x786 resolution, which is
not handled by those panels. This is a bit strange, because the
connector implemented by the panel reports proper native mode to drm and
userspace. 'modetest -c' shows the right resolution. Also when I run
'modetest -s' with the panel's native resolution then the test pattern
is correctly displayed on all three boards.
Then I've played a bit with the analogix code and it looks that this
1024x768 mode is some kind default mode which comes from
analogix_dp_bridge_edid_read() function, which has been introduced by
this patchset. When I removed DRM_BRIDGE_OP_EDID flag from bridge->ops,
then I got it finally working again properly on all three boards. I hope
this helps fixing this issue.
Thank you for your help with the investigation. :-)
Based on your helpful findings and Dmitry's earlier suggestions[0], it
is better to distinguish the &drm_bridge->ops of Analogix bridge based
on whether the downstream device is a panel, a bridge or neither.
1. If there is a panel after, the &drm_bridge->ops should be set to
DRM_BRIDGE_OP_MODES | DRM_BRIDGE_OP_DETECT.
Since the &drm_bridge->ops of panel_bridge is DRM_BRIDGE_OP_MODES and
the panel-edp driver reads EDID in &drm_panel_funcs.get_modes(), the
DRM_BRIDGE_OP_EDID should be removed to ensure proper invocation for the
&drm_bridge_funcs.get_modes() of panel_bridge.
2. If there is a bridge after, the &drm_bridge->ops should be set to NULL.
The OP_EDID and OP_MODES supports depends on the next bridge rather than
the Analogix bridge. According to your investigation, nxp-ptn3460
supports &drm_bridge_funcs.edid_read() while parade-ps8625 do not.
Additionally, since some bridges does not support
&drm_bridge_funcs.detect(), which regards as connector_status_connected
by default according to
drm_helper_probe_detect()(drivers/gpu/drm_probe_helper.c), the
connection status should also depends on the next bridge rather than the
Analogix bridge.
3. If there is neither a panel nor a bridge, the &drm_bridge->ops should
be set to DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_DETECT.
In this case, the Analogix DP driver may work in the DP mode, so the
OP_EDID and OP_DETECT supports should be helpful.
Best regards,
Damon
[0]https://lore.kernel.org/all/incxmqneeurgli5h6p3hn3bgztxrzyk5eq2h5nq4lgzalohslq@mvehvr4cgyim/
