linux-kernel - Re: [PATCH v3 2/9] drm/sun4i: tcon: Add TCON LCD support for R40

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Date:   Thu, 2 Jan 2020 22:04:40 +0530
From:   Jagan Teki <jagan@...rulasolutions.com>
To:     Maxime Ripard <mripard@...nel.org>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Rob Herring <robh+dt@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        linux-amarula <linux-amarula@...rulasolutions.com>
Subject: Re: [PATCH v3 2/9] drm/sun4i: tcon: Add TCON LCD support for R40

On Thu, Jan 2, 2020 at 9:17 PM Maxime Ripard <mripard@...nel.org> wrote:
>
> On Thu, Jan 02, 2020 at 09:10:31PM +0530, Jagan Teki wrote:
> > On Thu, Jan 2, 2020 at 4:24 PM Maxime Ripard <mripard@...nel.org> wrote:
> > >
> > > On Tue, Dec 31, 2019 at 06:35:21PM +0530, Jagan Teki wrote:
> > > > TCON LCD0, LCD1 in allwinner R40, are used for managing
> > > > LCD interfaces like RGB, LVDS and DSI.
> > > >
> > > > Like TCON TV0, TV1 these LCD0, LCD1 are also managed via
> > > > tcon top.
> > > >
> > > > Add support for it, in tcon driver.
> > > >
> > > > Signed-off-by: Jagan Teki <jagan@...rulasolutions.com>
> > > > ---
> > > > Changes for v3:
> > > > - none
> > > >
> > > >  drivers/gpu/drm/sun4i/sun4i_tcon.c | 8 ++++++++
> > > >  1 file changed, 8 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> > > > index fad72799b8df..69611d38c844 100644
> > > > --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> > > > +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> > > > @@ -1470,6 +1470,13 @@ static const struct sun4i_tcon_quirks sun8i_a83t_tv_quirks = {
> > > >       .has_channel_1          = true,
> > > >  };
> > > >
> > > > +static const struct sun4i_tcon_quirks sun8i_r40_lcd_quirks = {
> > > > +     .supports_lvds          = true,
> > > > +     .has_channel_0          = true,
> > > > +     /* TODO Need to support TCON output muxing via GPIO pins */
> > > > +     .set_mux                = sun8i_r40_tcon_tv_set_mux,
> > >
> > > What is this muking about? And why is it a TODO?
> >
> > Muxing similar like how TCON TOP handle TV0, TV1 I have reused the
> > same so-that it would configure de port selection via
> > sun8i_tcon_top_de_config
> >
> > TCON output muxing have gpio with GPIOD and GPIOH bits, which select
> > which of LCD or TV TCON outputs to the LCD function pins. I have
> > marked these has TODO for further support as mentioned by Chen-Yu in
> > v1[1].
>
> It should be in the commit log.

Make sense.

>
> What's the plan to support that when needed? And that means that the
> LCD and TV outputs are mutually exclusive? We should at the very least
> check that both aren't enabled at the same time.

Yes, LCD or TV within the outselect seems to be mutually exclusive.
Like LCD0 or TV0 can output to GPIOD incase of TV0_OUTSEL and LCD1 or
TV1 can output to GPIOH incase of TV1_OUTSEL. I think checking them
before configuring TCON_TOP_PORT_SEL_REG would make sense, let me know
if you have any suggestions?