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Message-ID: <c75d107a-44cb-4df3-b583-13719df1f8be@arm.com>
Date: Wed, 15 Nov 2023 14:53:04 +0000
From: Robin Murphy <robin.murphy@....com>
To: Bibek Kumar Patro <quic_bibekkum@...cinc.com>, will@...nel.org,
joro@...tes.org, dmitry.baryshkov@...aro.org, a39.skl@...il.com,
konrad.dybcio@...aro.org, quic_pkondeti@...cinc.com,
quic_molvera@...cinc.com
Cc: linux-arm-msm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
linux-kernel@...r.kernel.org, qipl.kernel.upstream@...cinc.com
Subject: Re: [PATCH v2 1/3] iommu/arm-smmu: introduction of ACTLR for custom
prefetcher settings
On 2023-11-15 1:54 pm, Bibek Kumar Patro wrote:
>
>>> @@ -467,6 +505,9 @@ static struct arm_smmu_device
>>> *qcom_smmu_create(struct arm_smmu_device *smmu,
>>> qsmmu->smmu.impl = impl;
>>> qsmmu->cfg = data->cfg;
>>>
>>> + if (data->actlrcfg && (data->actlrcfg->size))
>>> + qsmmu->actlrcfg = data->actlrcfg;
>>
>> Do we really need to replicate multiple parts of the data, or would it
>> be sensible to just replace qsmmu->cfg with qsmmu->data and handle the
>> further dereferences in the places that want them?
>>
>
> Mm, could not understand this properly. :( Could you help explain more
> please?
> As per my understanding aren't data and qsmmu different structures.
> qcom_smmu is a superset of arm_smmu housing additonal properties
> and qcom_smmu_match_data is kind of a superset of arm_smmu_impl with
> additional specific implmentations, so both needs to be in place?
> Apologies if I understood your statement incorrectly.
My point is that the data is static and constant, so there's really no
point storing multiple pointers into different bits of it. So rather than:
qsmmu->cfg = data->cfg;
qssmu->actlrcfg = data->actlrcfg;
...
do_something(qsmmu->cfg);
...
do_other_thing(qsmmu->actlrcfg);
we can just store the one pointer and have:
qsmmu->data = data;
...
do_something(qsmmu->data->cfg);
...
do_other_thing(qsmmu->data->actlrcfg);
Thanks,
Robin.
>>> +
>>> return &qsmmu->smmu;
>>> }
>>>
>>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>>> b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>>> index 593910567b88..4b6862715070 100644
>>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>>> @@ -9,6 +9,7 @@
>>> struct qcom_smmu {
>>> struct arm_smmu_device smmu;
>>> const struct qcom_smmu_config *cfg;
>>> + const struct actlr_config *actlrcfg;
>>> bool bypass_quirk;
>>> u8 bypass_cbndx;
>>> u32 stall_enabled;
>>> @@ -25,6 +26,7 @@ struct qcom_smmu_config {
>>> };
>>>
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