linux-kernel - Re: [PATCH] drm/panel: Add prepare_prev

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Date:   Thu, 3 Aug 2023 10:19:19 -0700
From:   Jessica Zhang <quic_jesszhan@...cinc.com>
To:     <neil.armstrong@...aro.org>, Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
CC:     <quic_abhinavk@...cinc.com>, <quic_parellan@...cinc.com>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/panel: Add prepare_prev_first flag to Visionox
 VTDR6130



On 7/31/2023 6:00 AM, Neil Armstrong wrote:
> Hi,
> 
> On 26/07/2023 00:56, Jessica Zhang wrote:
>> Due to a recent introduction of the pre_enable_prev_first bridge flag 
>> [1],
>> the panel driver will be probed before the DSI is enabled, causing the
>> DCS commands to fail to send.
>>
>> Ensure that DSI is enabled before panel probe by setting the
>> prepare_prev_first flag for the panel.
> 
> Well this is specific to MSM DSI driver, it's not related at all to the 
> panel.

Hi Neil,

I think there might be some confusion caused by the commit message -- 
instead of "enabled before panel probe", it should be "enabled before 
panel pre_enable()" as the panel on commands are sent during prepare(), 
which is matched to bridge pre_enable().

IIRC the general rule is that the panel driver should set the 
prepare_prev_first flag if the on commands are sent during pre_enable(), 
so I'll keep the code change but correct the commit message if that's ok 
with you.

Thanks,

Jessica Zhang

> 
> Neil
> 
>>
>> [1] commit 4fb912e5e190 ("drm/bridge: Introduce pre_enable_prev_first 
>> to alter bridge init order")
>>
>> Fixes: 2349183d32d8 ("drm/panel: add visionox vtdr6130 DSI panel driver")
>> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
>> ---
>>   drivers/gpu/drm/panel/panel-visionox-vtdr6130.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c 
>> b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
>> index bb0dfd86ea67..e1363e128e7e 100644
>> --- a/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
>> +++ b/drivers/gpu/drm/panel/panel-visionox-vtdr6130.c
>> @@ -296,6 +296,7 @@ static int visionox_vtdr6130_probe(struct 
>> mipi_dsi_device *dsi)
>>       dsi->format = MIPI_DSI_FMT_RGB888;
>>       dsi->mode_flags = MIPI_DSI_MODE_VIDEO | 
>> MIPI_DSI_MODE_NO_EOT_PACKET |
>>                 MIPI_DSI_CLOCK_NON_CONTINUOUS;
>> +    ctx->panel.prepare_prev_first = true;
>>       drm_panel_init(&ctx->panel, dev, &visionox_vtdr6130_panel_funcs,
>>                  DRM_MODE_CONNECTOR_DSI);
>>
>> ---
>> base-commit: 28a5c036b05fc5c935cc72d76abd3589825ea9cd
>> change-id: 20230717-visionox-vtdr-prev-first-e00ae02eec9f
>>
>> Best regards,
>