Re: [PATCH 0/7] drm/msm/dpu: simplify VBIF handling

[Dmitry Baryshkov]

On Mon, Mar 02, 2026 at 01:45:39PM +0100, Konrad Dybcio wrote:
> On 2/27/26 7:36 PM, Dmitry Baryshkov wrote:
> > Once Konrad asked, what is the use for VBIF_NRT. Answering to his
> > question revealed that it's not actually used by the DPU driver.
> > 
> > There are two VBIF interfaces two memory, VBIF_RT and VBIF_NRT with
> > VBIF_NRT being used only for the offscreen rotator, a separate block
> > performing writeback operation with the optional 90 degree rotation.
> > This block will require a separate isntance of the DPU driver, and it is
> > not supported at this point.
> > 
> > The only exception to that rule is MSM8996, where VBIF_NRT has also been
> > used for outputting all writeback data. The DPU driver don't support WB
> > on that platform and most likely will not in the close feature.
> > 
> > The missing features don't match the extra complexity required to
> > support two VBIF interfaces, so drop the second one and all the options
> > to support it.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
> > ---
> 
> This leaves a trailing 'bool is_rt' in struct dpu_vbif_set_qos_params.
> 
> I'm not sure whether/if we're going to use that specific set of functions
> with rotator support, but we should probably retain (and at some point
> recheck) the dpu_vbif_cfg->qos_nrt_tbl data that the catalog houses

is_rt and qos_nrt_tbl are related to the WB support, so they can't go
away.

> 
> Konrad

-- 
With best wishes
Dmitry