Re: [PATCH] drm/dsi: Add _NO_ to MIPI_DSI_* flags disabling features

[Nicolas Boichat <drinkcat@chromium.org>]

On Mon, Feb 22, 2021 at 3:21 PM Andrzej Hajda <a.hajda@samsung.com> wrote:
>
> Hi Nicolas,
>
> W dniu 22.02.2021 o 06:31, Nicolas Boichat pisze:
> > On Mon, Feb 22, 2021 at 3:08 AM Laurent Pinchart
> > <laurent.pinchart@ideasonboard.com> wrote:
> >> Hi Nicolas,
> >>
> >> Thank you for the patch.
> >>
> >> On Thu, Feb 11, 2021 at 11:33:55AM +0800, Nicolas Boichat wrote:
> >>> Many of the DSI flags have names opposite to their actual effects,
> >>> e.g. MIPI_DSI_MODE_EOT_PACKET means that EoT packets will actually
> >>> be disabled. Fix this by including _NO_ in the flag names, e.g.
> >>> MIPI_DSI_MODE_NO_EOT_PACKET.
> >>>
> >>> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
> >> This looks good to me, it increases readability.
> >>
> >> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >>
> >> Please however see the end of the mail for a comment.
>
>
> Reviewed-by: Andrzej Hajda <andrzej.hajda@samsung.com>
>
> And comment at the end.
>
> >>
> >>> ---
> >>> I considered adding _DISABLE_ instead, but that'd make the
> >>> flag names a big too long.
> >>>
> >>> Generated with:
> >>> flag=MIPI_DSI_MODE_VIDEO_HFP; git grep $flag | cut -f1 -d':' | \
> >>>    xargs -I{} sed -i -e "s/$flag/MIPI_DSI_MODE_VIDEO_NO_HFP/" {}
> >>> flag=MIPI_DSI_MODE_VIDEO_HBP; git grep $flag | cut -f1 -d':' | \
> >>>    xargs -I{} sed -i -e "s/$flag/MIPI_DSI_MODE_VIDEO_NO_HBP/" {}
> >>> flag=MIPI_DSI_MODE_VIDEO_HSA; git grep $flag | cut -f1 -d':' | \
> >>>    xargs -I{} sed -i -e "s/$flag/MIPI_DSI_MODE_VIDEO_NO_HSA/" {}
> >>> flag=MIPI_DSI_MODE_EOT_PACKET; git grep $flag | cut -f1 -d':' | \
> >>>    xargs -I{} sed -i -e "s/$flag/MIPI_DSI_MODE_NO_EOT_PACKET/" {}
> >>> (then minor format changes)
> >> Ever tried coccinelle ? :-)
> > Fun project for next time ,-)
> >
> >>>   drivers/gpu/drm/bridge/adv7511/adv7533.c             | 2 +-
> >>>   drivers/gpu/drm/bridge/analogix/anx7625.c            | 2 +-
> >>>   drivers/gpu/drm/bridge/cdns-dsi.c                    | 4 ++--
> >>>   drivers/gpu/drm/bridge/tc358768.c                    | 2 +-
> >>>   drivers/gpu/drm/exynos/exynos_drm_dsi.c              | 8 ++++----
> >>>   drivers/gpu/drm/mcde/mcde_dsi.c                      | 2 +-
> >>>   drivers/gpu/drm/mediatek/mtk_dsi.c                   | 2 +-
> >>>   drivers/gpu/drm/msm/dsi/dsi_host.c                   | 8 ++++----
> >>>   drivers/gpu/drm/panel/panel-asus-z00t-tm5p5-n35596.c | 2 +-
> >>>   drivers/gpu/drm/panel/panel-dsi-cm.c                 | 2 +-
> >>>   drivers/gpu/drm/panel/panel-elida-kd35t133.c         | 2 +-
> >>>   drivers/gpu/drm/panel/panel-khadas-ts050.c           | 2 +-
> >>>   drivers/gpu/drm/panel/panel-leadtek-ltk050h3146w.c   | 2 +-
> >>>   drivers/gpu/drm/panel/panel-leadtek-ltk500hd1829.c   | 2 +-
> >>>   drivers/gpu/drm/panel/panel-novatek-nt35510.c        | 2 +-
> >>>   drivers/gpu/drm/panel/panel-osd-osd101t2587-53ts.c   | 2 +-
> >>>   drivers/gpu/drm/panel/panel-samsung-s6d16d0.c        | 2 +-
> >>>   drivers/gpu/drm/panel/panel-samsung-s6e63j0x03.c     | 2 +-
> >>>   drivers/gpu/drm/panel/panel-samsung-s6e63m0-dsi.c    | 2 +-
> >>>   drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c        | 4 ++--
> >>>   drivers/gpu/drm/panel/panel-sharp-ls043t1le01.c      | 2 +-
> >>>   drivers/gpu/drm/panel/panel-simple.c                 | 2 +-
> >>>   drivers/gpu/drm/panel/panel-sony-acx424akp.c         | 2 +-
> >>>   drivers/gpu/drm/panel/panel-xinpeng-xpp055c272.c     | 2 +-
> >>>   include/drm/drm_mipi_dsi.h                           | 8 ++++----
> >>>   25 files changed, 36 insertions(+), 36 deletions(-)
> >>>
> >>> []
> >>> diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> >>> index 360e6377e84b..ba91cf22af51 100644
> >>> --- a/include/drm/drm_mipi_dsi.h
> >>> +++ b/include/drm/drm_mipi_dsi.h
> >>> @@ -119,15 +119,15 @@ struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node);
> >>>   /* enable hsync-end packets in vsync-pulse and v-porch area */
> >>>   #define MIPI_DSI_MODE_VIDEO_HSE              BIT(4)
> >> We're mixing bits that enable a feature and bits that disable a feature.
> >> Are these bits defined in the DSI spec, or internal to DRM ? In the
> >> latter case, would it make sense to standardize on one "polarity" ? That
> >> would be a more intrusive change in drivers though.
> > Yes, that'd require auditing every single code path and reverse the
> > logic as needed. I'm not volunteering for that ,-P (hopefully the
> > current change is still an improvement).
> >
> > Hopefully real DSI experts can comment (Andrzej?), I think the default
> > are sensible settings?
>
> Hehe, "real DSI expert" :), ok I've read spec few times :)
>
> If I remember correctly the spec did not prioritizes these modes, specs
> are publicly available if somebody want to check it feel free.
>
> These values were taken from defaults for Exynos DSI, as nobody at the
> time has better idea.
>
> We could try to optimize it by looking for example in different dsi
> hosts defaults, or maybe dsi devices, but I am not sure if it is worth time.

Little git grep experiment:
# git grep compatible -- drivers/gpu/drm/panel | wc -l
219 panels in total

# sed -n 's/.*\(MIPI_DSI[^ \t]*\).*/\1/p' include/drm/drm_mipi_dsi.h |
xargs -I{} sh -c 'echo -n {}:; git grep {} | wc -l'
MIPI_DSI_MODE_VIDEO:68
MIPI_DSI_MODE_VIDEO_BURST:23
MIPI_DSI_MODE_VIDEO_SYNC_PULSE:20
MIPI_DSI_MODE_VIDEO_AUTO_VERT:1
MIPI_DSI_MODE_VIDEO_HSE:6
MIPI_DSI_MODE_VIDEO_NO_HFP:1
MIPI_DSI_MODE_VIDEO_NO_HBP:1
MIPI_DSI_MODE_VIDEO_NO_HSA:1
MIPI_DSI_MODE_VSYNC_FLUSH:1
MIPI_DSI_MODE_NO_EOT_PACKET:16
MIPI_DSI_CLOCK_NON_CONTINUOUS:19
MIPI_DSI_MODE_LPM:54

At least, there is no regret flipping the polarity for
MIPI_DSI_MODE_VIDEO_NO_HFP/HBP/HSA.

I guess we could consider flipping the default for MIPI_DSI_MODE_VIDEO
and MIPI_DSI_MODE_LPM (some drivers set the flags in code, instead of
a structure, so I think MIPI_DSI_MODE_VIDEO is almost always set).

Still not volunteering ,-P

>
> This solution is good for me.
>
>
> Regards
>
> Andrzej
>
>
> >
> >
> >>>   /* disable hfront-porch area */
> >>> -#define MIPI_DSI_MODE_VIDEO_HFP              BIT(5)
> >>> +#define MIPI_DSI_MODE_VIDEO_NO_HFP   BIT(5)
> >>>   /* disable hback-porch area */
> >>> -#define MIPI_DSI_MODE_VIDEO_HBP              BIT(6)
> >>> +#define MIPI_DSI_MODE_VIDEO_NO_HBP   BIT(6)
> >>>   /* disable hsync-active area */
> >>> -#define MIPI_DSI_MODE_VIDEO_HSA              BIT(7)
> >>> +#define MIPI_DSI_MODE_VIDEO_NO_HSA   BIT(7)
> >>>   /* flush display FIFO on vsync pulse */
> >>>   #define MIPI_DSI_MODE_VSYNC_FLUSH    BIT(8)
> >>>   /* disable EoT packets in HS mode */
> >>> -#define MIPI_DSI_MODE_EOT_PACKET     BIT(9)
> >>> +#define MIPI_DSI_MODE_NO_EOT_PACKET  BIT(9)
> >>>   /* device supports non-continuous clock behavior (DSI spec 5.6.1) */
> >>>   #define MIPI_DSI_CLOCK_NON_CONTINUOUS        BIT(10)
> >>>   /* transmit data in low power */
> >> --
> >> Regards,
> >>
> >> Laurent Pinchart
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