Re: [PATCH v3 14/21] drm/sun4i: tcon: multiply the vtotal when not in interlace

[Chen-Yu Tsai]

On Wed, May 17, 2017 at 3:40 PM, Maxime Ripard
<maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote:
> It appears that the total vertical resolution needs to be doubled when
> we're not in interlaced. Make sure that is the case.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index 62e254aedb57..a0f9a8a516c7 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -153,7 +153,7 @@ static int sun4i_tcon_get_clk_delay(struct drm_display_mode *mode,
>  void sun4i_tcon0_mode_set(struct sun4i_tcon *tcon,
>                           struct drm_display_mode *mode)
>  {
> -       unsigned int bp, hsync, vsync;
> +       unsigned int bp, hsync, vsync, vtotal;
>         u8 clk_delay;
>         u32 val = 0;
>
> @@ -192,9 +192,26 @@ void sun4i_tcon0_mode_set(struct sun4i_tcon *tcon,
>         DRM_DEBUG_DRIVER("Setting vertical total %d, backporch %d\n",
>                          mode->crtc_vtotal, bp);
>
> +       /*
> +        * The vertical resolution needs to be doubled in all
> +        * cases. We could use crtc_vtotal and always multiply by two,
> +        * but that leads to a rounding error in interlace when vtotal
> +        * is odd.
> +        *
> +        * This happens with TV's PAL for example, where vtotal will
> +        * be 625, crtc_vtotal 312, and thus crtc_vtotal * 2 will be
> +        * 624, which apparently confuses the hardware.
> +        *
> +        * To work around this, we will always use vtotal, and
> +        * multiply by two only if we're not in interlace.
> +        */
> +       vtotal = mode->vtotal;
> +       if (!(mode->flags & DRM_MODE_FLAG_INTERLACE))
> +               vtotal = vtotal * 2;
> +
>         /* Set vertical display timings */
>         regmap_write(tcon->regs, SUN4I_TCON0_BASIC2_REG,
> -                    SUN4I_TCON0_BASIC2_V_TOTAL(mode->crtc_vtotal * 2) |
> +                    SUN4I_TCON0_BASIC2_V_TOTAL(vtotal) |
>                      SUN4I_TCON0_BASIC2_V_BACKPORCH(bp));
>
>         /* Set Hsync and Vsync length */
> @@ -279,9 +296,9 @@ void sun4i_tcon1_mode_set(struct sun4i_tcon *tcon,
>         /* Set vertical display timings */
>         bp = mode->crtc_vtotal - mode->crtc_vsync_start;
>         DRM_DEBUG_DRIVER("Setting vertical total %d, backporch %d\n",
> -                        mode->vtotal, bp);
> +                        mode->crtc_vtotal, bp);

You should duplicate the logic from channel 0 to channel 1.
In fact, interlaced modes happen predominantly on channel 1,
for composite and HDMI modes.

ChenYu

>         regmap_write(tcon->regs, SUN4I_TCON1_BASIC4_REG,
> -                    SUN4I_TCON1_BASIC4_V_TOTAL(mode->vtotal) |
> +                    SUN4I_TCON1_BASIC4_V_TOTAL(mode->crtc_vtotal * 2) |
>                      SUN4I_TCON1_BASIC4_V_BACKPORCH(bp));
>
>         /* Set Hsync and Vsync length */
> --
> git-series 0.9.1