Re: [PATCH 7/9] drm/rcar-du: dsi: Clean up handling of DRM mode flags

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Wed, Sep 24, 2025 at 04:36:00AM +0200, Marek Vasut wrote:
> On 9/24/25 3:18 AM, Sebastian Reichel wrote:
> 
> Hello Sebastian,
> 
> > On Tue, Sep 23, 2025 at 04:26:16PM +0300, Laurent Pinchart wrote:
> >> I wonder if the DRM_MODE_FLAG_P[HV]SYNC flags are always the exact
> >> opposite of DRM_MODE_FLAG_N[HV]SYNC. It's probably fine to assume that
> >> here. A quick grep showed one panel driver setting both the N and P
> >> flags (drivers/gpu/drm/panel/panel-sitronix-st7789v.c, see
> >> t28cp45tn89_mode, which I assume is a bug - Sebastian, could you check
> >> that ?).
> > 
> > Yeah, it was supposed to be
> > 
> > static const struct drm_display_mode t28cp45tn89_mode = {
> >      ...
> >      .flags = DRM_MODE_FLAG_PVSYNC | DRM_MODE_FLAG_NHSYNC
> > };
> > 
> > The driver works with the panel, because the driver defaults to
> > DRM_MODE_FLAG_N[HV]SYNC and ignores the related flags, so just the
> > DRM_MODE_FLAG_P[HV]SYNC one is applied:
> > 
> > static int st7789v_prepare(struct drm_panel *panel)
> > {
> >      ...
> > 
> > 	if (ctx->info->mode->flags & DRM_MODE_FLAG_PVSYNC)
> > 		polarity |= ST7789V_RGBCTRL_VSYNC_HIGH;
> > 	if (ctx->info->mode->flags & DRM_MODE_FLAG_PHSYNC)
> > 		polarity |= ST7789V_RGBCTRL_HSYNC_HIGH;
> > 
> >      ...
> > }
> > 
> > Greetings and thanks for the bug report,
> 
> Will you send a patch ? If so, please CC me, so I can provide RB.

Feel free to include my

    Reported-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

in that patch.

-- 
Regards,

Laurent Pinchart