linux-kernel - Re: [PATCH] drm/panel: kingdisplay-kd097d04: Disable EoTp

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Message-ID: <33e255dc-64f9-4e4f-82eb-6f5e9c1d63d4@dwurp.de>
Date: Wed, 29 Oct 2025 08:12:53 +0100
From: Sebastian Fleer <dev@...rp.de>
To: chf.fritz@...glemail.com
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
 Jessica Zhang <jesszhan0024@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panel: kingdisplay-kd097d04: Disable EoTp

Hi Christoph,

On 10/28/25 23:31, Christoph Fritz wrote:
 > Hi Sebastian
 >
 > On Tue, 2025-10-28 at 22:38 +0100, Sebastian Fleer wrote:
 >> Since commit d97e71e44937 ("drm/bridge: synopsys: dw-mipi-dsi: 
enable EoTp by
 >> default") panel output on an Acer Chromebook Tab 10 (google-dru) is 
corrupted.
 >> The tablet I use is equipped with a kingdisplay-kd097d04 panel, 
disabling EoTp
 >> restores the correct functionality.
 >>
 >> Fixes: d97e71e44937 ("drm/bridge: synopsys: dw-mipi-dsi: enable EoTp 
by default")
 >
 > Just to clarify: This is not a fix for that commit, it is a fix for the
 > panel driver itself.
 >
 > EoTp is the default in Linux, a panel driver cannot enable it, only
 > disable it.
 >
 > Commit d97e71e44937 ("drm/bridge: synopsys: dw-mipi-dsi: enable EoTp by
 > default") fixed a bug in the synopsys dw-mipi-dsi because EoTp was not
 > enabled there by default.
 >
 > Enabling EoTp in dw-mipi-dsi revealed an underlying issue in panel-
 > kingdisplay-kd097d04.
 >
 > That same issue appears if one would connect this panel to a different
 > mipi-dsi core (because there EoTp is also enabled by default).
 >
thanks for your clarification. You're right, this change is merely a 
workaround for the kingdisplay panel.
However, I'm in favor of keeping the "Fixes:" line since using bisect, 
commit d97e71e44937 ("drm/bridge: synopsys: dw-mipi-dsi: enable EoTp by
default") is found as the first commit that shows distorted output for 
that panel.
But I can make the nature of the change more clear in the commit 
message. Would that be OK for you?

Best regards,
Sebastian

 >> Signed-off-by: Sebastian Fleer <dev@...rp.de>
 >> ---
 >>   drivers/gpu/drm/panel/panel-kingdisplay-kd097d04.c | 2 +-
 >>   1 file changed, 1 insertion(+), 1 deletion(-)
 >>
 >> diff --git a/drivers/gpu/drm/panel/panel-kingdisplay-kd097d04.c 
b/drivers/gpu/drm/panel/panel-kingdisplay-kd097d04.c
 >> index 2fc7b0779b37..893af9b16756 100644
 >> --- a/drivers/gpu/drm/panel/panel-kingdisplay-kd097d04.c
 >> +++ b/drivers/gpu/drm/panel/panel-kingdisplay-kd097d04.c
 >> @@ -359,7 +359,7 @@ static int kingdisplay_panel_probe(struct 
mipi_dsi_device *dsi)
 >>   	dsi->lanes = 4;
 >>   	dsi->format = MIPI_DSI_FMT_RGB888;
 >>   	dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
 >> -			  MIPI_DSI_MODE_LPM;
 >> +			  MIPI_DSI_MODE_LPM | MIPI_DSI_MODE_NO_EOT_PACKET;
 >>
 >>   	kingdisplay = devm_drm_panel_alloc(&dsi->dev, 
__typeof(*kingdisplay), base,
 >>   					   &kingdisplay_panel_funcs,