linux-kernel - Re: [PATCH v5 1/5] drm/panel: jd9365da: Modify the method of sending commands

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Date: Mon, 24 Jun 2024 09:22:05 -0700
From: Doug Anderson <dianders@...gle.com>
To: Zhaoxiong Lv <lvzhaoxiong@...qin.corp-partner.google.com>
Cc: dmitry.torokhov@...il.com, robh@...nel.org, 
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, jikos@...nel.org, 
	benjamin.tissoires@...hat.co, hsinyi@...gle.com, jagan@...eble.ai, 
	neil.armstrong@...aro.org, quic_jesszhan@...cinc.com, 
	dmitry.baryshkov@...aro.org, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] drm/panel: jd9365da: Modify the method of sending commands

Hi,

On Mon, Jun 24, 2024 at 7:20 AM Zhaoxiong Lv
<lvzhaoxiong@...qin.corp-partner.google.com> wrote:
>
> Currently, the init_code of the jd9365da driver is placed
> in the enable() function and sent, but this seems to take
> a long time. It takes 17ms to send each instruction (an init
> code consists of about 200 instructions), so it takes
> about 3.5s to send the init_code. So we moved the sending
> of the inti_code to the prepare() function, and each
> instruction seemed to take only 25μs.
>
> We checked the DSI host and found that the difference in
> command sending time is caused by the different modes of
> the DSI host in prepare() and enable() functions.
> Our DSI Host only supports sending cmd in LP mode, The
> prepare() function can directly send init_code (LP->cmd)
> in LP mode, but the enable() function is in HS mode and
> needs to switch to LP mode before sending init code
> (HS->LP->cmd->HS). Therefore, it takes longer to send
> the command.
>
> Signed-off-by: Zhaoxiong Lv <lvzhaoxiong@...qin.corp-partner.google.com>
> ---
> Changes between V5 and V4:
> - 1. No changes.
>
> V4:https://lore.kernel.org/all/20240620080509.18504-2-lvzhaoxiong@huaqin.corp-partner.google.com/
>
> Changes between V4 and V3:
> - 1. Only move mipi_dsi_dcs_write_buffer from enable() function to prepare() function,
> -    and no longer use mipi_dsi_dcs_write_seq_multi.
>
> V3:https://lore.kernel.org/all/20240614145510.22965-2-lvzhaoxiong@huaqin.corp-partner.google.com/
>
> ---
>  .../gpu/drm/panel/panel-jadard-jd9365da-h3.c  | 24 +++++++++----------
>  1 file changed, 11 insertions(+), 13 deletions(-)

As mentioned in v4, it would be good if someone with more MIPI history
confirmed that this looks like a reasonable thing to do. However, the
code looks fine so I'll give:

Reviewed-by: Douglas Anderson <dianders@...omium.org>