Re: [PATCH v5 07/17] drm/sun4i: sun6i_mipi_dsi: Refactor vertical video start delay

From: Jagan Teki <jagan@amarulasolutions.com>
To: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Stephen Boyd <sboyd@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	linux-sunxi <linux-sunxi@googlegroups.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Chen-Yu Tsai <wens@csie.org>,
	Michael Trimarchi <michael@amarulasolutions.com>,
	linux-amarula@amarulasolutions.com,
	linux-clk <linux-clk@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v5 07/17] drm/sun4i: sun6i_mipi_dsi: Refactor vertical video start delay
Date: Tue, 11 Dec 2018 22:30:08 +0530	[thread overview]
Message-ID: <CAMty3ZBzOyAGwgOZwArbvnqtcvwMkJrqwGQ-q7+XFX-BVs34RQ@mail.gmail.com> (raw)
In-Reply-To: <20181211164900.wfmkmbrbj3nmlb3h@flea>

On Tue, Dec 11, 2018 at 10:19 PM Maxime Ripard
<maxime.ripard@bootlin.com> wrote:
>
> On Mon, Dec 10, 2018 at 09:47:19PM +0530, Jagan Teki wrote:
> > Video start delay can be computed by subtracting total vertical
> > timing with front porch timing and with adding 1 delay line for TCON.
> >
> > BSP code form BPI-M64-bsp is computing video start delay as
> > (from linux-sunxi/
> > drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)
> >
> > u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
> > => (panel->lcd_vt) - panel->lcd_y - (panel->lcd_vbp)
> > => (timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y)
> >    - panel->lcd_y - (panel->lcd_vbp)
> > => timmings->ver_front_porch + panel->lcd_vbp + panel->lcd_y
> >                            - panel->lcd_y - panel->lcd_vbp
> > => timmings->ver_front_porch
> >
> > So, update the start delay computation accordingly.
> >
> > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
>
> Even though it's a bit better now on my A33 board and I don't have the
> white stripes on the bottom of the display, there's still some
> flickering with your patches applied.
>
> Bisecting it seems to point at that patch, but reverting it doesn't
> make the issue go away, so it's not really clear which one exactly is
> at fault.
>
> So, just like I asked in your v4, twice,
>
> http://lists.infradead.org/pipermail/linux-arm-kernel/2018-November/615339.html

I don't know how can I comment here. Not quite clearly understand your
setup, because I have verified 3 different panels from different
vendors one with 2-lane, another with 4-lane and one with video format
and another one is burstmode format. I even verified with the clock
rate and register details.

Please suggest me, what can look further on this.

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