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References: <20230502010759.17282-1-aford173@gmail.com> <20230502010759.17282-4-aford173@gmail.com>
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From:   Adam Ford <aford173@gmail.com>
Date:   Thu, 4 May 2023 07:00:08 -0500
Message-ID: <CAHCN7x+7YWyvy+cDXcD2D5twJt_Ys6tP+TsLgjH4TgcORW0LPA@mail.gmail.com>
Subject: Re: [PATCH V3 3/7] drm: bridge: samsung-dsim: Fetch
 pll-clock-frequency automatically
To:     Alexander Stein <alexander.stein@ew.tq-group.com>
Cc:     dri-devel@lists.freedesktop.org, marex@denx.de,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Robert Foss <rfoss@kernel.org>,
        Jonas Karlman <jonas@kwiboo.se>, aford@beaconembedded.com,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        linux-kernel@vger.kernel.org,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Chen-Yu Tsai <wenst@chromium.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Jagan Teki <jagan@amarulasolutions.com>
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On Thu, May 4, 2023 at 4:21=E2=80=AFAM Alexander Stein
<alexander.stein@ew.tq-group.com> wrote:
>
> Am Dienstag, 2. Mai 2023, 03:07:55 CEST schrieb Adam Ford:
> > Make the pll-clock-frequency optional.  If it's present, use it
> > to maintain backwards compatibility with existing hardware.  If it
> > is absent, read clock rate of "sclk_mipi" to determine the rate.
> >
> > Signed-off-by: Adam Ford <aford173@gmail.com>
> > Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> > ---
> >  drivers/gpu/drm/bridge/samsung-dsim.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c
> > b/drivers/gpu/drm/bridge/samsung-dsim.c index bf4b33d2de76..2dc02a9e37c=
0
> > 100644
> > --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> > @@ -1726,12 +1726,20 @@ static int samsung_dsim_parse_dt(struct samsung=
_dsim
> > *dsi) {
> >       struct device *dev =3D dsi->dev;
> >       struct device_node *node =3D dev->of_node;
> > +     struct clk *pll_clk;
> >       int ret;
> >
> >       ret =3D samsung_dsim_of_read_u32(node, "samsung,pll-clock-frequen=
cy",
> >                                      &dsi->pll_clk_rate);
> > -     if (ret < 0)
> > -             return ret;
> > +
> > +     /* If it doesn't exist, read it from the clock instead of failing=
 */
> > +     if (ret < 0) {
> > +             pll_clk =3D devm_clk_get(dev, "sclk_mipi");
> > +             if (!IS_ERR(pll_clk))
> > +                     dsi->pll_clk_rate =3D clk_get_rate(pll_clk);
> > +             else
> > +                     return PTR_ERR(pll_clk);
> > +     }
> >
>
> Now that 'samsung,pll-clock-frequency' is optional the error in
> samsung_dsim_of_read_u32() should be changed. Otherwise you will get
> > /soc@0/bus@32c00000/dsi@32e10000: failed to get 'samsung,pll-clock-
> frequency' property

I'll change the message from err to info with a message that reads "no
samsung,pll-clock-frequency, using pixel clock"

Does that work?

adam
>
> Best regards,
> Alexander
>
> >       ret =3D samsung_dsim_of_read_u32(node, "samsung,burst-clock-
> frequency",
> >                                      &dsi->burst_clk_rate);
>
>
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