linux-kernel - Re: [PATCH 2/2] drm/panel: boe-tv101wum-nl6: Reduce lcm

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Date:   Mon, 9 Jan 2023 11:54:24 +0000
From:   Xinlei Lee (李昕磊) 
        <Xinlei.Lee@...iatek.com>
To:     "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "sam@...nborg.org" <sam@...nborg.org>,
        Jitao Shi (石记涛) <jitao.shi@...iatek.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH 2/2] drm/panel: boe-tv101wum-nl6: Reduce lcm_reset to send
 initial code time

On Mon, 2023-01-09 at 12:25 +0100, AngeloGioacchino Del Regno wrote:
> Il 06/01/23 04:05, xinlei.lee@...iatek.com ha scritto:
> > From: Xinlei Lee <xinlei.lee@...iatek.com>
> > 
> > Since the panel spec stipulates that the time from lcm_reset to DSI
> > to
> > send the initial code should be greater than 6ms and less than
> > 40ms,
> > so reduce the delay before sending the initial code and avoid panel
> > exceptions.
> > 
> > Fixes: a869b9db7adf ("drm/panel: support for boe tv101wum-nl6 wuxga
> > dsi video mode panel")
> > Signed-off-by: Xinlei Lee <xinlei.lee@...iatek.com>
> > ---
> >   drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c | 1 -
> >   1 file changed, 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > b/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > index 857a2f0420d7..f0093035f1ff 100644
> > --- a/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > +++ b/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > @@ -780,7 +780,6 @@ static const struct panel_init_cmd
> > inx_hj110iz_init_cmd[] = {
> >   };
> >   
> >   static const struct panel_init_cmd boe_init_cmd[] = {
> > -	_INIT_DELAY_CMD(24),
> 
> You said that should be greater than 6 and less than 40: perhaps on
> MediaTek
> platforms removing this delay is fine but we don't know about others
> - and this
> driver is for all platforms.
> 
> To stay on the safe side you should, at this point, replace this
> delay with
> 
> 	_INIT_DELAY_CMD(7);
> 
> Regards,
> Angelo
> 

Hi Angelo:

Thanks for your reply!

Please allow me to explain, in another dsi modification of this 
series, I reduced the delay of dsi's LP00->LP11 stage from 20ms to 1ms 
(to comply with dsi spec), in fact, in this file, the
boe_panel_prepare function The 6ms delay after pulling up lcm_reset
is before the 1ms mentioned just now, which ensures that the delay is 
within the specified range (7ms).

Do you still have doubts about my explanation?

Best Regards!
xinlei