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

From: Akhil P Oommen <quic_akhilpo@quicinc.com>
To: Doug Anderson <dianders@chromium.org>,
	Stephen Boyd <swboyd@chromium.org>,
	Taniya Das <quic_tdas@quicinc.com>, <quic_rjendra@quicinc.com>
Cc: freedreno <freedreno@lists.freedesktop.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Rob Clark <robdclark@gmail.com>,
	"Bjorn Andersson" <bjorn.andersson@linaro.org>,
	Jonathan Marek <jonathan@marek.ca>,
	Jordan Crouse <jordan@cosmicpenguin.net>,
	Matthias Kaehlcke <mka@chromium.org>,
	Andy Gross <agross@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Rob Herring <robh+dt@kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
	"Stephen Boyd" <swboyd@chromium.org>
Subject: Re: [PATCH v2 5/7] arm64: dts: qcom: sc7280: Update gpu register list
Date: Thu, 14 Jul 2022 11:10:29 +0530	[thread overview]
Message-ID: <c022538d-c616-8f1a-e1c2-c11b5f0de670@quicinc.com> (raw)
In-Reply-To: <CAD=FV=XzvcjS51q78BZ=FPCEVUDMD+VKJ70ksCm5V4qwHN_wRg@mail.gmail.com>

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@quicinc.com> wrote:
>> Update gpu register array with gpucc memory region.
>>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
>> ---
>>
>> (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.