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From:   Nicolas Boichat <drinkcat@chromium.org>
Date:   Wed, 3 Mar 2021 18:31:04 +0800
Message-ID: <CANMq1KAsvXZAjmYCMQsAUwpkzuA9-PRnNWkpsLuNbOkP6DixGA@mail.gmail.com>
Subject: Re: [PATCH] drm/dsi: Add _NO_ to MIPI_DSI_* flags disabling features
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Andrzej Hajda <a.hajda@samsung.com>,
        Robert Foss <robert.foss@linaro.org>,
        Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Emil Velikov <emil.velikov@collabora.com>,
        Inki Dae <inki.dae@samsung.com>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        Jonas Karlman <jonas@kwiboo.se>,
        Joonyoung Shim <jy0922.shim@samsung.com>,
        Jordan Crouse <jcrouse@codeaurora.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Maxime Ripard <mripard@kernel.org>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Rikard Falkeborn <rikard.falkeborn@gmail.com>,
        Rob Clark <robdclark@gmail.com>,
        Sam Ravnborg <sam@ravnborg.org>, Sean Paul <sean@poorly.run>,
        Seung-Woo Kim <sw0312.kim@samsung.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Xin Ji <xji@analogixsemi.com>,
        "open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        MSM <linux-arm-msm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        linux-samsung-soc <linux-samsung-soc@vger.kernel.org>
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On Mon, Mar 1, 2021 at 4:59 PM Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Thu, Feb 11, 2021 at 4:34 AM Nicolas Boichat <drinkcat@chromium.org> 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.
>
> Unless someone like me interpreted it literally...
>
> Like in these:
>
> >  drivers/gpu/drm/mcde/mcde_dsi.c                      | 2 +-
> >  drivers/gpu/drm/panel/panel-novatek-nt35510.c        | 2 +-
> >  drivers/gpu/drm/panel/panel-samsung-s6d16d0.c        | 2 +-
> >  drivers/gpu/drm/panel/panel-sony-acx424akp.c         | 2 +-
>
> > diff --git a/drivers/gpu/drm/mcde/mcde_dsi.c b/drivers/gpu/drm/mcde/mcde_dsi.c
> > index 2314c8122992..f4cdc3cfd7d0 100644
> > --- a/drivers/gpu/drm/mcde/mcde_dsi.c
> > +++ b/drivers/gpu/drm/mcde/mcde_dsi.c
> > @@ -760,7 +760,7 @@ static void mcde_dsi_start(struct mcde_dsi *d)
> >                 DSI_MCTL_MAIN_DATA_CTL_BTA_EN |
> >                 DSI_MCTL_MAIN_DATA_CTL_READ_EN |
> >                 DSI_MCTL_MAIN_DATA_CTL_REG_TE_EN;
> > -       if (d->mdsi->mode_flags & MIPI_DSI_MODE_EOT_PACKET)
> > +       if (d->mdsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
> >                 val |= DSI_MCTL_MAIN_DATA_CTL_HOST_EOT_GEN;
>
> If you read the code you can see that this is interpreted as inserting
> an EOT packet, so here you need to change the logic such:
>
> if (!d->mdsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
>     val |= DSI_MCTL_MAIN_DATA_CTL_HOST_EOT_GEN;
>
> This will make sure the host generates the EOT packet in HS mode
> *unless* the flag is set.
>
> (I checked the data sheet.)
>
> > diff --git a/drivers/gpu/drm/panel/panel-novatek-nt35510.c b/drivers/gpu/drm/panel/panel-novatek-nt35510.c
> > index b9a0e56f33e2..9d9334656803 100644
> > --- a/drivers/gpu/drm/panel/panel-novatek-nt35510.c
> > +++ b/drivers/gpu/drm/panel/panel-novatek-nt35510.c
> > @@ -899,7 +899,7 @@ static int nt35510_probe(struct mipi_dsi_device *dsi)
> >         dsi->hs_rate = 349440000;
> >         dsi->lp_rate = 9600000;
> >         dsi->mode_flags = MIPI_DSI_CLOCK_NON_CONTINUOUS |
> > -               MIPI_DSI_MODE_EOT_PACKET;
> > +               MIPI_DSI_MODE_NO_EOT_PACKET;
>
> Here you should just delete the MIPI_DSI_MODE_EOT_PACKET
> flag because this was used with the MCDE driver which interpret the
> flag literally.
>
> > diff --git a/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c b/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c
> > index 4aac0d1573dd..b04b9975e9b2 100644
> > --- a/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c
> > +++ b/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c
> > @@ -186,7 +186,7 @@ static int s6d16d0_probe(struct mipi_dsi_device *dsi)
> >          */
> >         dsi->mode_flags =
> >                 MIPI_DSI_CLOCK_NON_CONTINUOUS |
> > -               MIPI_DSI_MODE_EOT_PACKET;
> > +               MIPI_DSI_MODE_NO_EOT_PACKET;
>
> Same, just delete the flag.
>
> > --- a/drivers/gpu/drm/panel/panel-samsung-s6e63m0-dsi.c
> > +++ b/drivers/gpu/drm/panel/panel-samsung-s6e63m0-dsi.c
> > @@ -97,7 +97,7 @@ static int s6e63m0_dsi_probe(struct mipi_dsi_device *dsi)
> >         dsi->hs_rate = 349440000;
> >         dsi->lp_rate = 9600000;
> >         dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
> > -               MIPI_DSI_MODE_EOT_PACKET |
> > +               MIPI_DSI_MODE_NO_EOT_PACKET |
> >                 MIPI_DSI_MODE_VIDEO_BURST;
>
> Same, just delete the flag.
>
> > diff --git a/drivers/gpu/drm/panel/panel-sony-acx424akp.c b/drivers/gpu/drm/panel/panel-sony-acx424akp.c
> > index 065efae213f5..6b706cbf2f9c 100644
> > --- a/drivers/gpu/drm/panel/panel-sony-acx424akp.c
> > +++ b/drivers/gpu/drm/panel/panel-sony-acx424akp.c
> > @@ -450,7 +450,7 @@ static int acx424akp_probe(struct mipi_dsi_device *dsi)
> >         else
> >                 dsi->mode_flags =
> >                         MIPI_DSI_CLOCK_NON_CONTINUOUS |
> > -                       MIPI_DSI_MODE_EOT_PACKET;
> > +                       MIPI_DSI_MODE_NO_EOT_PACKET;
>
> Same, just delete the flag.
>
> These are all just semantic bugs due to the ambiguity of the flags, it is
> possible to provide a Fixes: flag for each file using this flag the wrong way
> but I dunno if it's worth it.

Wow nice catch.

I think we should fix all of those _before_ my patch is applied, with
proper Fixes tags so that this can be backported to stable branches,
even if it's a no-op. I can look into it but that may take a bit of
time.

Thanks,

>
> Yours,
> Linus Walleij