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

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Date:   Sat, 4 Jan 2020 15:20:14 +0100
From:   Maxime Ripard <mripard@...nel.org>
To:     Jagan Teki <jagan@...rulasolutions.com>
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

Hi,

On Thu, Jan 02, 2020 at 10:04:40PM +0530, Jagan Teki wrote:
> 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?

Making sure in atomic_check that TV and LCD are not used at the same
time, and then in encoders mode_set / enable mux the pins to our
encoders would be my first guess.

Maxime

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