linux-kernel - Re: [PATCH 5/5] ARM: dts: qcom: msm8974: add interconnect nodes

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Message-ID: <c26159f5-e6fe-07f1-51b3-50b72b258846@linaro.org>
Date:   Wed, 23 Oct 2019 16:39:21 +0300
From:   Georgi Djakov <georgi.djakov@...aro.org>
To:     Brian Masney <masneyb@...tation.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org, robh+dt@...nel.org,
        mark.rutland@....com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 5/5] ARM: dts: qcom: msm8974: add interconnect nodes

On 23.10.19 г. 15:47 ч., Brian Masney wrote:
> On Wed, Oct 23, 2019 at 02:50:19PM +0300, Georgi Djakov wrote:
>> On 13.10.19 г. 11:08 ч., Brian Masney wrote:
>>> Add interconnect nodes that's needed to support bus scaling.
>>>
>>> Signed-off-by: Brian Masney <masneyb@...tation.org>
>>> ---
>>>  arch/arm/boot/dts/qcom-msm8974.dtsi | 60 +++++++++++++++++++++++++++++
>>>  1 file changed, 60 insertions(+)
>>>
>>> diff --git a/arch/arm/boot/dts/qcom-msm8974.dtsi b/arch/arm/boot/dts/qcom-msm8974.dtsi
>>> @@ -1152,6 +1207,11 @@
>>>  				              "core",
>>>  				              "vsync";
>>>  
>>> +				interconnects = <&mmssnoc MNOC_MAS_GRAPHICS_3D &bimc BIMC_SLV_EBI_CH0>,
>>> +				                <&ocmemnoc OCMEM_VNOC_MAS_GFX3D &ocmemnoc OCMEM_SLV_OCMEM>;
>>
>> Who will be the requesting bandwidth to DDR and ocmem? Is it the display or GPU
>> or both? The above seem like GPU-related interconnects, so maybe these
>> properties should be in the GPU DT node.
> 
> The display is what currently requests the interconnect path,
> specifically mdp5_setup_interconnect() in
> drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c. The Freedreno GPU bindings
> currently don't have interconnect support. Maybe this is something that
> I should add to that driver as well?

The "mdp0-mem" and "mdp1-mem" paths mentioned in the mdp5_kms.c are the two
interconnects between the display and DDR memory. There is actually a patch [1]
to add to GPU bindings, but it seems that we missed to pick it up.

> 
>>> +				interconnect-names = "mdp0-mem",
>>> +				                     "mdp1-mem";
>>
>> As the second path is not to DDR, but to ocmem, it might be better to call it
>> something like "gpu-ocmem".
> 
> I used what mdp5_kms.c expected.

This is for the display and here [2] are some patches for the GPU. Not sure how
the NoCs are configured on 8974 by default, but if you notice any blue/black
screens, you may need to request bandwidth for display too.

Thanks,
Georgi

[1]
https://lore.kernel.org/r/1555703787-10897-1-git-send-email-jcrouse@codeaurora.org
[2] https://lore.kernel.org/r/20181220173026.3857-1-jcrouse@codeaurora.org