linux-kernel - Re: [PATCH v2 3/3] drm/panel: boe-tv101wum-nl6: Fine tune the panel power sequence

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Message-ID: <12828da82a646796642757c793f30e32dcbb4528.camel@mediatek.com>
Date:   Thu, 12 Jan 2023 10:00:43 +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 v2 3/3] drm/panel: boe-tv101wum-nl6: Fine tune the panel
 power sequence

On Tue, 2023-01-10 at 10:22 +0100, AngeloGioacchino Del Regno wrote:
> Il 10/01/23 06:54, xinlei.lee@...iatek.com ha scritto:
> > From: Xinlei Lee <xinlei.lee@...iatek.com>
> > 
> > For "boe,tv105wum-nw0" this special panel, it is stipulated in the
> > panel spec that MIPI needs to keep the LP11 state before the
> > lcm_reset pin is pulled high.
> > 
> > Signed-off-by: Xinlei Lee <xinlei.lee@...iatek.com>
> > ---
> >   drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > b/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > index f0093035f1ff..67df61de64ae 100644
> > --- a/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > +++ b/drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c
> > @@ -36,6 +36,7 @@ struct panel_desc {
> >   	const struct panel_init_cmd *init_cmds;
> >   	unsigned int lanes;
> >   	bool discharge_on_disable;
> > +	bool lp11_before_reset;
> >   };
> >   
> >   struct boe_panel {
> > @@ -1261,6 +1262,10 @@ static int boe_panel_prepare(struct
> > drm_panel *panel)
> >   
> >   	usleep_range(10000, 11000);
> >   
> > +	if (boe->desc->lp11_before_reset) {
> > +		mipi_dsi_dcs_nop(boe->dsi);
> 
> NOP will never reach the driveric if it is in reset, which should
> apparently be
> the state of it at that point in code.
> 
> I guess that you wanted to do that after LCM reset and before sending
> init cmds.
> 
> Regards,
> Angelo
> 

Hi Angelo:

To explain to you that in my patch, sending a NOP before lcm_reset is 
what this particular panel driver needs.

Indeed, the NOP will not reach the panel driveric before lcm_reset,
but the driveric specification stipulates that the MIPI signal needs
to be pulled high before lcm_reset is pulled high(NOP 
-> mtk_dsi_host_transfer -> mtk_dsi_lane_ready) . In order to avoid 
special driver initialization exceptions, this control was added.

Best Regards!
xinlei