linux-kernel - Re: [PATCH v3 1/2] drm/panel: jd9365da: Move "exit sleep mode" and "set display on" cmds

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Message-ID: <0df40f72-f1d5-4049-a6e5-04d973c7a0c7@linaro.org>
Date: Mon, 19 Aug 2024 17:44:45 +0200
From: neil.armstrong@...aro.org
To: Doug Anderson <dianders@...omium.org>,
 Jessica Zhang <quic_jesszhan@...cinc.com>
Cc: Zhaoxiong Lv <lvzhaoxiong@...qin.corp-partner.google.com>,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de,
 hsinyi@...gle.com, airlied@...il.com, daniel@...ll.ch, jagan@...eble.ai,
 dmitry.baryshkov@...aro.org, jani.nikula@...ux.intel.com,
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] drm/panel: jd9365da: Move "exit sleep mode" and
 "set display on" cmds

On 12/08/2024 17:45, Doug Anderson wrote:
> Jessica,
> 
> On Thu, Aug 8, 2024 at 3:56 PM Jessica Zhang <quic_jesszhan@...cinc.com> wrote:
>>
>>
>>
>> On 8/7/2024 3:04 AM, Zhaoxiong Lv wrote:
>>> Move the "exit sleep mode" and "set display on" command from
>>> enable() to init() function.
>>>
>>> As mentioned in the patch:
>>> https://lore.kernel.org/all/20240624141926.5250-2-lvzhaoxiong@huaqin.corp-partner.google.com/
>>>
>>> The Mediatek Soc DSI host has different modes in prepare() and
>>> enable() functions, prepare() is in LP mode and enable() is in
>>> HS mode. Since the "exit sleep mode" and "set display on"
>>> command must also be sent in LP mode, so we also move "exit
>>> sleep mode" and "set display on" command to the init() function.
>>>
>>> We have no other actions in the enable() function after moves
>>> "exit sleep mode" and "set display on", and we checked the call
>>> of the enable() function during the "startup" process. It seems
>>> that only one judgment was made in drm_panel_enabel(). If the
>>> panel does not define enable(), the judgment will skip the
>>> enable() and continue execution. This does not seem to have
>>> any other effect, and we found that some drivers also seem
>>> to have no enable() function added, for example:
>>> panel-asus-z00t-tm5p5-n35596 / panel-boe-himax8279d...
>>> In addition, we briefly tested the kingdisplay_kd101ne3 panel and
>>> melfas_lmfbx101117480 panel, and it seems that there is no garbage
>>> on the panel, so we delete enable() function.
>>>
>>> After moving the "exit sleep mode" and "set display on" command
>>> to the init() function, we no longer need additional delay
>>> judgment, so we delete variables "exit_sleep_to_display_on_delay_ms"
>>> and "display_on_delay_ms".
>>>
>>> Reviewed-by: Douglas Anderson <dianders@...omium.org>
>>> Signed-off-by: Zhaoxiong Lv <lvzhaoxiong@...qin.corp-partner.google.com>
>>
>> Acked-by: Jessica Zhang <quic_jesszhan@...cinc.com>
> 
> Does this Ack mean you're confident enough about this patch that we
> should go ahead and merge it, or do you think we should wait on
> anything else (like Neil getting a chance to look at it)? As I
> mentioned in my reply to the cover letter [1] the patches look OK to
> me but I still don't consider myself to have a wonderful understanding
> of the intricacies of MIPI DSI. If you think this is OK from a MIPI
> DSI point of view then we can land it...

I don't have an advanced MIPI DSI knowledge, but they simple remove unneeded
sleeps between dcs commands, so if they are confident they can be removed I agree...

Neil

> 
> [1] https://lore.kernel.org/r/CAD=FV=WCw6pAump-PUFCW0cgbRY+5_2tPNLe=hN3-dnXD=B6MA@mail.gmail.com
> 
> Thanks!
> 
> -Doug