linux-kernel - Re: [PATCH 12/15] drm/sun4i: tcon: multiply the vtotal when not in interlace

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Message-ID: <CAGb2v67t7O4AuSXUupB3EU7OZdxgQbeyB6qL_g3x_BXOFLg9Bg@mail.gmail.com>
Date:   Tue, 7 Mar 2017 18:05:17 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Chen-Yu Tsai <wens@...e.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH 12/15] drm/sun4i: tcon: multiply the vtotal when not in interlace

Hi,

On Tue, Mar 7, 2017 at 4:56 PM, Maxime Ripard
<maxime.ripard@...e-electrons.com> wrote:
> It appears that the total vertical resolution needs to be doubled when
> we're not in interlaced. Make sure that is the case.

This is true for both channels, though we handle them differently.

>
> Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> ---
>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index e44217fb4f6f..515fa56c1e6a 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -248,10 +248,13 @@ void sun4i_tcon1_mode_set(struct sun4i_tcon *tcon, struct drm_encoder *encoder,
>                      SUN4I_TCON1_BASIC3_H_BACKPORCH(bp));
>
>         bp = mode->crtc_vtotal - mode->crtc_vsync_start;
> +       val = mode->crtc_vtotal;
> +       if (!(mode->flags & DRM_MODE_FLAG_INTERLACE))
> +               val = val * 2;
>         DRM_DEBUG_DRIVER("Setting vertical total %d, backporch %d\n",
>                          mode->vtotal, bp);
>         regmap_write(tcon->regs, SUN4I_TCON1_BASIC4_REG,
> -                    SUN4I_TCON1_BASIC4_V_TOTAL(mode->vtotal) |
> +                    SUN4I_TCON1_BASIC4_V_TOTAL(val) |

For channel 0, the SUN4I_TCON0_BASIC2_V_TOTAL macro multiplies the passed in
value by 2. I think we should do the same for channel 1, and instead halve the
value passed in if we are outputting interlaced data. I think this makes more
sense because:

1) The register description for both channels are the same. Handling them
   consistently will result in less confusion, such as this one.

2) The definition of interlaced modes is a frame is separated into odd and
   even fields, with each field contains half the number of lines of the
   full frame. One field is displayed during each VSYNC cycle. The TCON does
   not know whether it's interlaced video or not. It only knows the display
   timings. In this case, the number of horizontal lines per cycle is key.

Regards
ChenYu

>                      SUN4I_TCON1_BASIC4_V_BACKPORCH(bp));
>
>         /* Set Hsync and Vsync length */
> --
> git-series 0.8.11