Re: [PATCH] drm: bridge: fsl-ldb: fixup mode on freq mismatch

[Marek Vasut]

On 12/2/24 6:03 PM, Nikolaus Voss wrote:
> On 02.12.2024 13:56, Marek Vasut wrote:
> > On 12/2/24 7:32 AM, Liu Ying wrote:
> > > On 11/27/2024, Nikolaus Voss wrote:
> > > > LDB clock has to be a fixed multiple of the pixel clock.
> > > > As LDB and pixel clock are derived from different clock sources
> > > > (at least on imx8mp), this constraint cannot be satisfied for
> > > > any pixel clock, which leads to flickering and incomplete
> > > > lines on the attached display.
> > > >
> > > > To overcome this, check this condition in mode_fixup() and
> > > > adapt the pixel clock accordingly.
> > > >
> > > > Cc: <stable@xxxxxxxxxxxxxxx>
> > >
> > > It looks like stable is not effectively Cc'ed.
> > > Need a Fixes tag?
> > Isn't this fix effectively superseded by series
> >
> > [PATCH 0/5] clk: Fix simple video pipelines on i.MX8
> >
> > ?
>
> Maybe. I wasn't aware of the series. Looking at it, the change is
> rather complex and not suitable for the stable series.
>
> My intention was to get a simple fix which doesn't potentially
> break anything. It wouldn't even break the patch series you mentioned.
I know, the proper fix is indeed complex and not yet fully figured out.

The fix for stable for existing hardware is similar to this commit I think:

4fbb73416b10 ("arm64: dts: imx8mp-phyboard-pollux: Set Video PLL1 
frequency to 506.8 MHz")