Re: [PATCH v2 5/7] arm64: dts: qcom: sc7280: Update gpu register list

[Akhil P Oommen]

On 7/12/2022 4:57 AM, Doug Anderson wrote:
> Hi,
>
> On Fri, Jul 8, 2022 at 11:00 PM Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx> wrote:
> > Update gpu register array with gpucc memory region.
> >
> > Signed-off-by: Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx>
> > ---
> >
> > (no changes since v1)
> >
> >   arch/arm64/boot/dts/qcom/sc7280.dtsi | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > index e66fc67..defdb25 100644
> > --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
> > @@ -2228,10 +2228,12 @@
> >                          compatible = "qcom,adreno-635.0", "qcom,adreno";
> >                          reg = <0 0x03d00000 0 0x40000>,
> >                                <0 0x03d9e000 0 0x1000>,
> > -                             <0 0x03d61000 0 0x800>;
> > +                             <0 0x03d61000 0 0x800>,
> > +                             <0 0x03d90000 0 0x2000>;
> >                          reg-names = "kgsl_3d0_reg_memory",
> >                                      "cx_mem",
> > -                                   "cx_dbgc";
> > +                                   "cx_dbgc",
> > +                                   "gpucc";
> This doesn't seem right. Shouldn't you be coordinating with the
> existing gpucc instead of reaching into its registers?
>
> -Doug
IIUC, qcom gdsc driver doesn't ensure hardware is collapsed since they 
are vote-able switches. Ideally, we should ensure that the hw has 
collapsed for gpu recovery because there could be transient votes from 
other subsystems like hypervisor using their vote register.

I am not sure how complex the plumbing to gpucc driver would be to allow 
gpu driver to check hw status. OTOH, with this patch, gpu driver does a 
read operation on a gpucc register which is in always-on domain. That 
means we don't need to vote any resource to access this register.

Stephen/Rajendra/Taniya, any suggestion?

-Akhil.