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

["CK Hu (胡俊光)" <ck.hu@mediatek.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@mediatek.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

> 
> Best regards
> Jens
> 
> > 
> > Signed-off-by: Shuijing Li <shuijing.li@mediatek.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;
> 
>