PROBLEM: Asus C201 video mode problems on HDMI hotplug (regression)

[Nick Bowler]

Hi Jose,

On 2017-12-02 17:11 +0000, Jose Abreu wrote:
> On 01-12-2017 00:11, Nick Bowler wrote:
> > Another data point... the following patch appears sufficient to
> > restore working behaviour.
[...]
> I don't think you can do this. The phy pll lock check is
> recommended and can indicate hw failure. Can you please check if
> this untested, uncompiled patch makes it work correctly ?

Your patch changes things.  With this applied on top of 4.15-rc1
it is failing 100% of the time instead of only half of the time.

I brought the original test equipment back to the setup so I can
see the video and pink bar again.  The symptoms remain the same
(unexpected size, pink bar, and no audio).

PS: your patch seems to have been line wrapped which made it a
bit annoying to apply.

> ------------------>8---------------
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index bf14214..456fc54 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -1669,7 +1669,7 @@ static void
> hdmi_disable_overflow_interrupts(struct dw_hdmi *hdmi)
>  
>  static int dw_hdmi_setup(struct dw_hdmi *hdmi, struct
> drm_display_mode *mode)
>  {
> -       int ret;
> +       int ret, vsync_len = mode->vsync_end - mode->vsync_start;
>  
>         hdmi_disable_overflow_interrupts(hdmi);
>  
> @@ -1722,6 +1722,14 @@ static int dw_hdmi_setup(struct dw_hdmi
> *hdmi, struct drm_display_mode *mode)
>                 return ret;
>         hdmi->phy.enabled = true;
>  
> +       /* Reset all clock domains */
> +       hdmi_writeb(hdmi, 0x00, HDMI_MC_SWRSTZ);
> +
> +       /* Rewrite vsync register to latch previous written values */
> +       if (mode->flags & DRM_MODE_FLAG_INTERLACE)
> +               vsync_len /= 2;
> +       hdmi_writeb(hdmi, vsync_len, HDMI_FC_VSYNCINWIDTH);
> +
>         /* HDMI Initialization Step B.3 */
>         dw_hdmi_enable_video_path(hdmi);
>  
> ------------------>8---------------
>
> I would expect this patch to end your wrong image issue but the
> audio part may be a different problem.

It is very consistent: pink bar <=> no audio.

My suspicion is that the audio problem is just the wrong video mode
on the sink side messing things up, but I have no way of confirming
that (that I know of).

Thanks,
  Nick