Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230515235713.232939-1-aford173@gmail.com> <20230515235713.232939-5-aford173@gmail.com>
 <CAMty3ZAU3NG8yk1dFB4Y3QtCZ7j7XUTqKHkJVKhhOduc4V5XpQ@mail.gmail.com>
In-Reply-To: <CAMty3ZAU3NG8yk1dFB4Y3QtCZ7j7XUTqKHkJVKhhOduc4V5XpQ@mail.gmail.com>
From:   Adam Ford <aford173@gmail.com>
Date:   Wed, 17 May 2023 06:14:23 -0500
Message-ID: <CAHCN7xKweWg2OtvWzBaBMzEQgV9ychK+U9J3=Z+-0XwR4cHrqA@mail.gmail.com>
Subject: Re: [PATCH V6 4/6] drm: bridge: samsung-dsim: Select GENERIC_PHY_MIPI_DPHY
To:     Jagan Teki <jagan@amarulasolutions.com>
Cc:     dri-devel@lists.freedesktop.org, aford@beaconembedded.com,
        Frieder Schrempf <frieder.schrempf@kontron.de>,
        Chen-Yu Tsai <wenst@chromium.org>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Robert Foss <rfoss@kernel.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Inki Dae <inki.dae@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Marek Vasut <marex@denx.de>, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Wed, May 17, 2023 at 6:05=E2=80=AFAM Jagan Teki <jagan@amarulasolutions.=
com> wrote:
>
> Hi Adam,
>
> On Tue, May 16, 2023 at 5:27=E2=80=AFAM Adam Ford <aford173@gmail.com> wr=
ote:
> >
> > In order to support variable DPHY timings, it's necessary
> > to enable GENERIC_PHY_MIPI_DPHY so phy_mipi_dphy_get_default_config
> > can be used to determine the nominal values for a given resolution
> > and refresh rate.
> >
> > Signed-off-by: Adam Ford <aford173@gmail.com>
> > Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> > Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> > Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> > ---
> >  drivers/gpu/drm/bridge/Kconfig | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kc=
onfig
> > index f076a09afac0..82c68b042444 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -227,6 +227,7 @@ config DRM_SAMSUNG_DSIM
> >         select DRM_KMS_HELPER
> >         select DRM_MIPI_DSI
> >         select DRM_PANEL_BRIDGE
> > +       select GENERIC_PHY_MIPI_DPHY
>
> Is it really required? phy is optional as it is not required for
> imx8mm/n/p as of now. May be we can add it while supporting it.

This was added to the series because build errors were reported
without it due to the fact that I added calls to
phy_mipi_dphy_get_default_config_for_hsclk.
Selecting this config option guarantees
phy_mipi_dphy_get_default_config_for_hsclk will be built and removes
the build error for Exynos and some 32-bit builds.

phy_mipi_dphy_get_default_config_for_hsclk sets the DSI configurations
like lpx, hs_exit, clk_prepare, clk_zero, clk_trail, hs_prepare,
hs_zero and hs_trail and those need to be
dynamic in order to functional at various resolutions.  I did try
leaving the hard-coded values you used, and I wasn't successful in
getting much to sync.

adam

>
> Thanks,
> Jagan.