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SubjectRe: [PATCH 1/2] perf/smmuv3: Don't reserve the register space that overlaps with the SMMUv3
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On 2021-01-19 01:59, Zhen Lei wrote:
> Some SMMUv3 implementation embed the Perf Monitor Group Registers (PMCG)
> inside the first 64kB region of the SMMU. Since SMMU and PMCG are managed
> by two separate drivers, and this driver depends on ARM_SMMU_V3, so the
> SMMU driver reserves the corresponding resource first, this driver should
> not reserve the corresponding resource again. Otherwise, a resource
> reservation conflict is reported during boot.
>
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
> drivers/perf/arm_smmuv3_pmu.c | 42 ++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 40 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> index 74474bb322c3f26..dcce085431c6ce8 100644
> --- a/drivers/perf/arm_smmuv3_pmu.c
> +++ b/drivers/perf/arm_smmuv3_pmu.c
> @@ -761,6 +761,44 @@ static void smmu_pmu_get_acpi_options(struct smmu_pmu *smmu_pmu)
> dev_notice(smmu_pmu->dev, "option mask 0x%x\n", smmu_pmu->options);
> }
>
> +static void __iomem *
> +smmu_pmu_get_and_ioremap_resource(struct platform_device *pdev,
> + unsigned int index,
> + struct resource **out_res)
> +{
> + int ret;
> + void __iomem *base;
> + struct resource *res;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> + if (!res) {
> + dev_err(&pdev->dev, "invalid resource\n");
> + return IOMEM_ERR_PTR(-EINVAL);
> + }
> + if (out_res)
> + *out_res = res;
> +
> + ret = region_intersects(res->start, resource_size(res),
> + IORESOURCE_MEM, IORES_DESC_NONE);
> + if (ret == REGION_INTERSECTS) {
> + /*
> + * The resource has already been reserved by the SMMUv3 driver.
> + * Don't reserve it again, just do devm_ioremap().
> + */
> + base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
> + } else {
> + /*
> + * The resource may have not been reserved by any driver, or
> + * has been reserved but not type IORESOURCE_MEM. In the latter
> + * case, devm_ioremap_resource() reports a conflict and returns
> + * IOMEM_ERR_PTR(-EBUSY).
> + */
> + base = devm_ioremap_resource(&pdev->dev, res);
> + }

What if the PMCG driver simply happens to probe first?

Robin.

> +
> + return base;
> +}
> +
> static int smmu_pmu_probe(struct platform_device *pdev)
> {
> struct smmu_pmu *smmu_pmu;
> @@ -793,7 +831,7 @@ 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);
> + smmu_pmu->reg_base = smmu_pmu_get_and_ioremap_resource(pdev, 0, &res_0);
> if (IS_ERR(smmu_pmu->reg_base))
> return PTR_ERR(smmu_pmu->reg_base);
>
> @@ -801,7 +839,7 @@ static int smmu_pmu_probe(struct platform_device *pdev)
>
> /* Determine if page 1 is present */
> if (cfgr & SMMU_PMCG_CFGR_RELOC_CTRS) {
> - smmu_pmu->reloc_base = devm_platform_ioremap_resource(pdev, 1);
> + smmu_pmu->reloc_base = smmu_pmu_get_and_ioremap_resource(pdev, 1, NULL);
> if (IS_ERR(smmu_pmu->reloc_base))
> return PTR_ERR(smmu_pmu->reloc_base);
> } else {
>

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