[PATCH 1/2] drm/vc4: Correct lbm size and calculation

[Maxime Ripard]

Hi Lucas,

On Thu, Jan 21, 2021 at 05:26:22PM +0100, Lucas Nussbaum wrote:
> Hi Maxime,
> 
> On 21/01/21 at 12:04 +0100, Maxime Ripard wrote:
> > Hi Lucas, Ryutaroh,
> > 
> > On Thu, Jan 21, 2021 at 11:57:58AM +0100, Maxime Ripard wrote:
> > > From: Dom Cobley <popcornmix at gmail.com>
> > > 
> > > LBM base address is measured in units of pixels per cycle.
> > > That is 4 for 2711 (hvs5) and 2 for 2708.
> > > 
> > > We are wasting 75% of lbm by indexing without the scaling.
> > > But we were also using too high a size for the lbm resulting
> > > in partial corruption (right hand side) of vertically
> > > scaled images, usually at 4K or lower resolutions with more layers.
> > > 
> > > The physical RAM of LBM on 2711 is 8 * 1920 * 16 * 12-bit
> > > (pixels are stored 12-bits per component regardless of format).
> > > 
> > > The LBM adress indexes work in units of pixels per clock,
> > > so for 4 pixels per clock that means we have 32 * 1920 = 60K
> > > 
> > > Fixes: c54619b0bfb3 ("drm/vc4: Add support for the BCM2711 HVS5")
> > > Signed-off-by: Dom Cobley <popcornmix at gmail.com>
> > > Signed-off-by: Maxime Ripard <maxime at cerno.tech>
> > 
> > This one should fix your issue
> > 
> > Feel free to test it and let me know if it's not the case
> 
> I confirm that the patches fix the issue I was seeing.

Great. Can I add your Tested-by (and Ryutaroh, can I add yours as well?)

Maxime
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