linux-kernel - Re: [PATCH v2 1/1] iommu/arm-smmu: Log CBFRSYNRA register on context fault

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Date:   Tue, 23 Apr 2019 12:12:52 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>, joro@...tes.org,
        will.deacon@....com, iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, bjorn.andersson@...aro.org
Subject: Re: [PATCH v2 1/1] iommu/arm-smmu: Log CBFRSYNRA register on context
 fault

On 22/04/2019 08:10, Vivek Gautam wrote:
> Bits[15:0] in CBFRSYNRA register contain information about
> StreamID of the incoming transaction that generated the
> fault. Dump CBFRSYNRA register to get this info.
> This is specially useful in a distributed SMMU architecture
> where multiple masters are connected to the SMMU.
> SID information helps to quickly identify the faulting
> master device.
> 
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
> 
> Changes since v1:
>   - Addressed review comments, given by Bjorn, for nits.
> 
>   drivers/iommu/arm-smmu-regs.h | 2 ++
>   drivers/iommu/arm-smmu.c      | 7 +++++--
>   2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu-regs.h b/drivers/iommu/arm-smmu-regs.h
> index a1226e4ab5f8..e9132a926761 100644
> --- a/drivers/iommu/arm-smmu-regs.h
> +++ b/drivers/iommu/arm-smmu-regs.h
> @@ -147,6 +147,8 @@ enum arm_smmu_s2cr_privcfg {
>   #define CBAR_IRPTNDX_SHIFT		24
>   #define CBAR_IRPTNDX_MASK		0xff
>   
> +#define ARM_SMMU_GR1_CBFRSYNRA(n)	(0x400 + ((n) << 2))
> +
>   #define ARM_SMMU_GR1_CBA2R(n)		(0x800 + ((n) << 2))
>   #define CBA2R_RW64_32BIT		(0 << 0)
>   #define CBA2R_RW64_64BIT		(1 << 0)
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 045d93884164..e000473f8205 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -575,7 +575,9 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
>   	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>   	struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
>   	struct arm_smmu_device *smmu = smmu_domain->smmu;
> +	void __iomem *gr1_base = ARM_SMMU_GR1(smmu);
>   	void __iomem *cb_base;
> +	u32 cbfrsynra;

Nit: I would simply add to the existing "u32 fsr, fsynr;" declaration, 
but that's the sort of thing that could hopefully be fixed up when 
applying (or otherwise I might bulldoze it anyway in my eventual rework 
of register accesses throughout the driver). Regardless,

Reviewed-by: Robin Murphy <robin.murphy@....com>

>   	cb_base = ARM_SMMU_CB(smmu, cfg->cbndx);
>   	fsr = readl_relaxed(cb_base + ARM_SMMU_CB_FSR);
> @@ -585,10 +587,11 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
>   
>   	fsynr = readl_relaxed(cb_base + ARM_SMMU_CB_FSYNR0);
>   	iova = readq_relaxed(cb_base + ARM_SMMU_CB_FAR);
> +	cbfrsynra = readl_relaxed(gr1_base + ARM_SMMU_GR1_CBFRSYNRA(cfg->cbndx));
>   
>   	dev_err_ratelimited(smmu->dev,
> -	"Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cb=%d\n",
> -			    fsr, iova, fsynr, cfg->cbndx);
> +	"Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n",
> +			    fsr, iova, fsynr, cbfrsynra, cfg->cbndx);
>   
>   	writel(fsr, cb_base + ARM_SMMU_CB_FSR);
>   	return IRQ_HANDLED;
>