Re: [PATCH] perf/smmuv3: Allow sharing MMIO registers with the SMMU driver

[Tuan Phan <tuanphan@amperemail.onmicrosoft.com>]

> On Apr 21, 2020, at 8:57 AM, Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:
> 
> Some Arm SMMUv3 implementations, for example Arm CoreLink MMU-600, embed
> the PMCG registers into the SMMU MMIO regions. It currently causes probe
> failure because the PMU and SMMU drivers request overlapping resources.
> 
> Avoid the conflict by calling devm_ioremap() directly from the PMU
> driver. We loose some sanity-checking of the memory map provided by
> firmware, which doesn't seem catastrophic.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
> 
> So this is the simplest solution, and I don't think we're missing much
> by skipping the resource reservation. I've also been exploring a more
> complex approach [1] which has the SMMU driver perform resource
> reservation on behalf of the PMU driver, but I'm not sure it's
> necessary.
> 
> Please test, I've only tried the RevC FastModel using devicetree so far.
> 
> [1] https://jpbrucker.net/git/linux/log/?h=smmu/pmu
> ---
> drivers/perf/arm_smmuv3_pmu.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> index ca183a53a7f10..ad63d1e73333f 100644
> --- a/drivers/perf/arm_smmuv3_pmu.c
> +++ b/drivers/perf/arm_smmuv3_pmu.c
> @@ -730,8 +730,8 @@ static void smmu_pmu_get_acpi_options(struct smmu_pmu *smmu_pmu)
> 
> static int smmu_pmu_probe(struct platform_device *pdev)
> {
> +	struct resource *res_0, *res_1;
> 	struct smmu_pmu *smmu_pmu;
> -	struct resource *res_0;
> 	u32 cfgr, reg_size;
> 	u64 ceid_64[2];
> 	int irq, err;
> @@ -759,18 +759,32 @@ static int smmu_pmu_probe(struct platform_device *pdev)
> 		.capabilities	= PERF_PMU_CAP_NO_EXCLUDE,
> 	};
> 
> +	/*
> +	 * If the PMCG registers are embedded into the SMMU regions, the
> +	 * resources have to be shared with the SMMU driver. Use ioremap()
> +	 * rather than ioremap_resource() to avoid conflicts.
> +	 */
> 	res_0 = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -	smmu_pmu->reg_base = devm_ioremap_resource(dev, res_0);
> -	if (IS_ERR(smmu_pmu->reg_base))
> -		return PTR_ERR(smmu_pmu->reg_base);
> +	if (!res_0)
> +		return -ENXIO;
> +
> +	smmu_pmu->reg_base = devm_ioremap(dev, res_0->start,
> +					  resource_size(res_0));
> +	if (!smmu_pmu->reg_base)
> +		return -ENOMEM;
> 
> 	cfgr = readl_relaxed(smmu_pmu->reg_base + SMMU_PMCG_CFGR);
> 
> 	/* Determine if page 1 is present */
> 	if (cfgr & SMMU_PMCG_CFGR_RELOC_CTRS) {
> -		smmu_pmu->reloc_base = devm_platform_ioremap_resource(pdev, 1);
> -		if (IS_ERR(smmu_pmu->reloc_base))
> -			return PTR_ERR(smmu_pmu->reloc_base);
> +		res_1 = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +		if (!res_1)
> +			return -ENXIO;
> +
> +		smmu_pmu->reloc_base = devm_ioremap(dev, res_1->start,
> +						    resource_size(res_1));
> +		if (!smmu_pmu->reloc_base)
> +			return -ENOMEM;

I tested this patch on HW, however I need to add one more following change to make it works

@@ -2854,7 +2854,7 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
        }
        ioaddr = res->start;
 
-       smmu->base = devm_ioremap_resource(dev, res);
+       smmu->base = devm_ioremap(dev, res->start, resource_size(res));
        if (IS_ERR(smmu->base))
                return PTR_ERR(smmu->base);


> 	} else {
> 		smmu_pmu->reloc_base = smmu_pmu->reg_base;
> 	}
> -- 
> 2.26.0
> 
> 
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