linux-kernel - Re: [PATCH v13 6/6] iommu/arm-smmu: add support for PRR bit setup

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Message-ID: <bc2d6a8e-4446-4311-8745-4a4fdb8bca3f@quicinc.com>
Date: Mon, 15 Jul 2024 16:31:28 +0530
From: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@...aro.org>, Rob Clark <robdclark@...il.com>
CC: <will@...nel.org>, <robin.murphy@....com>, <joro@...tes.org>,
        <jgg@...pe.ca>, <jsnitsel@...hat.com>, <robh@...nel.org>,
        <krzysztof.kozlowski@...aro.org>, <quic_c_gdjako@...cinc.com>,
        <dmitry.baryshkov@...aro.org>, <iommu@...ts.linux.dev>,
        <linux-arm-msm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        Rob Clark <robdclark@...omium.org>
Subject: Re: [PATCH v13 6/6] iommu/arm-smmu: add support for PRR bit setup



On 7/11/2024 3:31 AM, Konrad Dybcio wrote:
> On 10.07.2024 7:01 PM, Rob Clark wrote:
>> On Tue, Jul 9, 2024 at 12:43 PM Bibek Kumar Patro
>> <quic_bibekkum@...cinc.com> wrote:
> 
> [...]
> 
>> If there is a clean break, such as all smmu-500 have PRR and all
>> smmu-v2 do not, then it would be reasonable to use the compat strings.
>> If not, I think we need a different way.
> 
> if (a reserved-memory region is passed in dt) {
> 	init_prr()
> }
> 

This would have been a straight forward way to pass as a check for PRR
support, but as I mentioned in the above thread reserved-memory region 
is not required if gfx/drm allocates the page.
So I think compatible string would be more approachable way?

Thanks & regards,
Bibek

> Konrad