linux-kernel - Re: [PATCH v2] mediatek: dsi: Correct calculation formula of PHY Timing

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Message-ID: <20241124213853.06c1bd33@book>
Date: Sun, 24 Nov 2024 21:38:53 +0100
From: Jens Ziller <zillerbaer@....de>
To: "CK Hu (胡俊光)" <ck.hu@...iatek.com>
Cc: "Shuijing Li (李水静)" <Shuijing.Li@...iatek.com>,
 "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>, "Jitao Shi (
 石记涛)" <jitao.shi@...iatek.com>, "daniel@...ll.ch"
 <daniel@...ll.ch>, "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 Project_Global_Chrome_Upstream_Group
 <Project_Global_Chrome_Upstream_Group@...iatek.com>, "airlied@...il.com"
 <airlied@...il.com>, "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>, "matthias.bgg@...il.com"
 <matthias.bgg@...il.com>, AngeloGioacchino Del Regno
 <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v2] mediatek: dsi: Correct calculation formula of PHY
 Timing

Am Thu, 21 Nov 2024 03:50:02 +0000
schrieb CK Hu (胡俊光) <ck.hu@...iatek.com>:

> Hi, Shuijing:
> 
> On Sun, 2024-10-27 at 14:32 +0100, Jens Ziller wrote:
> > External email : Please do not click links or open attachments
> > until you have verified the sender or the content.
> > 
> > 
> > Am Fri, 12 Apr 2024 11:11:39 +0800
> > schrieb Shuijing Li <shuijing.li@...iatek.com>:
> > 
> > > This patch correct calculation formula of PHY timing.
> > > The spec define HS-PREPARE should be from 40ns+4*UI(44ns) to
> > > 85ns+6*UI(91ns). But current duration is 88ns and is near the
> > > boundary. So this patch make the duration to 64ns so it is near
> > > the safe range.
> > 
> > Hi Shuijing,
> > 
> > with this patch the panel in the Tentacruel ASUS Chromebook CM14
> > (CM1402F) flickers. There are 1 or 2 times per second a black panel.
> > Stable Kernel 6.11.5 and mainline 6.12-rc4 works only when I reverse
> > this patch. There's a bug inside. Can you please check that?
> 
> Please help Jens to fix this bug.
> Otherwise, I've to revert this patch.
>
> Regards,
> CK

I'am not be able to fix that. This patch must be reverted that the
actual kernel runs on my Chromebook. Please revert this patch.

Regards
Jens

> 
> > 
> > Best regards
> > Jens
> > 
> > > 
> > > Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
> > > ---
> > > Changes in v2:
> > > Add a commit to describe the improvements to this patch in detail,
> > > per suggestion frome previous thread:
> > > https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20240315072945.19502-1-shuijing.li@mediatek.com/__;!!CTRNKA9wMg0ARbw!nA3Auuq2W3qyf3a8OtzDvLICN_xfq5zUozp_-Wo7Q4jR9l6qKlxiWNC4TZPXQa8W08veWhokHyRrvCodcpg$
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_dsi.c | 33
> > > +++++++++++++++--------------- 1 file changed, 17 insertions(+),
> > > 16 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > > b/drivers/gpu/drm/mediatek/mtk_dsi.c index
> > > a2fdfc8ddb15..d1bd7d671880 100644 ---
> > > a/drivers/gpu/drm/mediatek/mtk_dsi.c +++
> > > b/drivers/gpu/drm/mediatek/mtk_dsi.c @@ -235,22 +235,23 @@ static
> > > void mtk_dsi_phy_timconfig(struct mtk_dsi *dsi) u32 data_rate_mhz
> > > = DIV_ROUND_UP(dsi->data_rate, 1000000); struct mtk_phy_timing
> > > *timing = &dsi->phy_timing;
> > > 
> > > -     timing->lpx = (60 * data_rate_mhz / (8 * 1000)) + 1;
> > > -     timing->da_hs_prepare = (80 * data_rate_mhz + 4 * 1000) /
> > > 8000;
> > > -     timing->da_hs_zero = (170 * data_rate_mhz + 10 * 1000) /
> > > 8000 + 1 -
> > > -                          timing->da_hs_prepare;
> > > -     timing->da_hs_trail = timing->da_hs_prepare + 1;
> > > -
> > > -     timing->ta_go = 4 * timing->lpx - 2;
> > > -     timing->ta_sure = timing->lpx + 2;
> > > -     timing->ta_get = 4 * timing->lpx;
> > > -     timing->da_hs_exit = 2 * timing->lpx + 1;
> > > -
> > > -     timing->clk_hs_prepare = 70 * data_rate_mhz / (8 * 1000);
> > > -     timing->clk_hs_post = timing->clk_hs_prepare + 8;
> > > -     timing->clk_hs_trail = timing->clk_hs_prepare;
> > > -     timing->clk_hs_zero = timing->clk_hs_trail * 4;
> > > -     timing->clk_hs_exit = 2 * timing->clk_hs_trail;
> > > +     timing->lpx = (80 * data_rate_mhz / (8 * 1000)) + 1;
> > > +     timing->da_hs_prepare = (59 * data_rate_mhz + 4 * 1000) /
> > > 8000 + 1;
> > > +     timing->da_hs_zero = (163 * data_rate_mhz + 11 * 1000) /
> > > 8000 + 1 -
> > > +             timing->da_hs_prepare;
> > > +     timing->da_hs_trail = (78 * data_rate_mhz + 7 * 1000) / 8000
> > > + 1; +
> > > +     timing->ta_go = 4 * timing->lpx;
> > > +     timing->ta_sure = 3 * timing->lpx / 2;
> > > +     timing->ta_get = 5 * timing->lpx;
> > > +     timing->da_hs_exit = (118 * data_rate_mhz / (8 * 1000)) + 1;
> > > +
> > > +     timing->clk_hs_prepare = (57 * data_rate_mhz / (8 * 1000)) +
> > > 1;
> > > +     timing->clk_hs_post = (65 * data_rate_mhz + 53 * 1000) /
> > > 8000 + 1;
> > > +     timing->clk_hs_trail = (78 * data_rate_mhz + 7 * 1000) /
> > > 8000 + 1;
> > > +     timing->clk_hs_zero = (330 * data_rate_mhz / (8 * 1000)) + 1
> > > -
> > > +             timing->clk_hs_prepare;
> > > +     timing->clk_hs_exit = (118 * data_rate_mhz / (8 * 1000)) +
> > > 1;
> > > 
> > >       timcon0 = timing->lpx | timing->da_hs_prepare << 8 |
> > >                 timing->da_hs_zero << 16 | timing->da_hs_trail <<
> > > 24;
> > 
> >