linux-kernel - Re: [PATCH v4 1/2] perf/smmuv3: Don't reserve the PMCG register spaces

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Date:   Mon, 1 Feb 2021 12:54:12 +0000
From:   Will Deacon <will@...nel.org>
To:     Zhen Lei <thunder.leizhen@...wei.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Mark Rutland <mark.rutland@....com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
Subject: Re: [PATCH v4 1/2] perf/smmuv3: Don't reserve the PMCG register
 spaces

On Sat, Jan 30, 2021 at 03:14:13PM +0800, Zhen Lei wrote:
> According to the SMMUv3 specification:
> Each PMCG counter group is represented by one 4KB page (Page 0) with one
> optional additional 4KB page (Page 1), both of which are at IMPLEMENTATION
> DEFINED base addresses.
> 
> This means that the PMCG register spaces may be within the 64KB pages of
> the SMMUv3 register space. When both the SMMU and PMCG drivers reserve
> their own resources, a resource conflict occurs.
> 
> To avoid this conflict, don't reserve the PMCG regions.
> 
> Suggested-by: Robin Murphy <robin.murphy@....com>
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  drivers/perf/arm_smmuv3_pmu.c | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> index 74474bb322c3f26..5e894f957c7b935 100644
> --- a/drivers/perf/arm_smmuv3_pmu.c
> +++ b/drivers/perf/arm_smmuv3_pmu.c
> @@ -793,17 +793,30 @@ static int smmu_pmu_probe(struct platform_device *pdev)
>  		.capabilities	= PERF_PMU_CAP_NO_EXCLUDE,
>  	};
>  
> -	smmu_pmu->reg_base = devm_platform_get_and_ioremap_resource(pdev, 0, &res_0);
> -	if (IS_ERR(smmu_pmu->reg_base))
> -		return PTR_ERR(smmu_pmu->reg_base);
> +	/*
> +	 * The register spaces of the PMCG may be in the register space of
> +	 * other devices. For example, SMMU. Therefore, the PMCG resources are
> +	 * not reserved to avoid resource conflicts with other drivers.
> +	 */
> +	res_0 = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res_0)
> +		return ERR_PTR(-EINVAL);

I tried to apply this, but you've got your return type in a muddle:

@@ @@
+drivers/perf/arm_smmuv3_pmu.c: In function ‘smmu_pmu_probe’:
+drivers/perf/arm_smmuv3_pmu.c:803:10: warning: returning ‘void *’ from a function with return type ‘int’ makes integer from pointer without a cast [-Wint-conversion]
+  803 |   return ERR_PTR(-EINVAL);
+      |          ^~~~~~~~~~~~~~~~
+drivers/perf/arm_smmuv3_pmu.c:803:31: warning: incorrect type in return expression (different base types) [sparse]
+drivers/perf/arm_smmuv3_pmu.c:803:31:    expected int [sparse]
+drivers/perf/arm_smmuv3_pmu.c:803:31:    got void * [sparse]
+drivers/perf/arm_smmuv3_pmu.c:806:10: warning: returning ‘void *’ from a function with return type ‘int’ makes integer from pointer without a cast [-Wint-conversion]
+  806 |   return ERR_PTR(-ENOMEM);
+      |          ^~~~~~~~~~~~~~~~
+drivers/perf/arm_smmuv3_pmu.c:806:31: warning: incorrect type in return expression (different base types) [sparse]
+drivers/perf/arm_smmuv3_pmu.c:806:31:    expected int [sparse]
+drivers/perf/arm_smmuv3_pmu.c:806:31:    got void * [sparse]
+drivers/perf/arm_smmuv3_pmu.c:816:11: warning: returning ‘void *’ from a function with return type ‘int’ makes integer from pointer without a cast [-Wint-conversion]
+  816 |    return ERR_PTR(-EINVAL);
+      |           ^~~~~~~~~~~~~~~~
+drivers/perf/arm_smmuv3_pmu.c:816:39: warning: incorrect type in return expression (different base types) [sparse]
+drivers/perf/arm_smmuv3_pmu.c:816:39:    expected int [sparse]
+drivers/perf/arm_smmuv3_pmu.c:816:39:    got void * [sparse]
+drivers/perf/arm_smmuv3_pmu.c:819:11: warning: returning ‘void *’ from a function with return type ‘int’ makes integer from pointer without a cast [-Wint-conversion]
+  819 |    return ERR_PTR(-ENOMEM);
+      |           ^~~~~~~~~~~~~~~~
+drivers/perf/arm_smmuv3_pmu.c:819:39: warning: incorrect type in return expression (different base types) [sparse]
+drivers/perf/arm_smmuv3_pmu.c:819:39:    expected int [sparse]
+drivers/perf/arm_smmuv3_pmu.c:819:39:    got void * [sparse]

Will