linux-kernel - Re: [PATCH] iommu/arm-smmu: clear cache lock bit of ACR

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Message-ID: <20160503125041.GA18127@linux-7smt.suse>
Date:	Tue, 3 May 2016 20:50:43 +0800
From:	Peng Fan <van.freenix@...il.com>
To:	Robin Murphy <robin.murphy@....com>
Cc:	will.deacon@....com, joro@...tes.org,
	linux-arm-kernel@...ts.infradead.org,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/arm-smmu: clear cache lock bit of ACR

Hi Robin,

On Tue, May 03, 2016 at 12:15:52PM +0100, Robin Murphy wrote:
>On 03/05/16 11:15, Peng Fan wrote:
>>According MMU-500 TRM, section 3.7.1 Auxiliary Control registers,
>>You can modify ACTLR only when the ACR.CACHE_LOCK bit is 0.
>>
>>So before clearing ARM_MMU500_ACTLR_CPRE of each context bank,
>>need clear CACHE_LOCK bit of ACR register first.
>
>Ah, good catch - I think I misread CACHE_LOCK as resetting to 0, and
>proceeded to forget about it. However, it's only present in MMU-500r2
>onwards, so we'd also want to check IDR7 before touching ACR.

Thanks for comments. I'll add code to check IDR7 and send out V2.

Thanks,
Peng.

>
>Thanks,
>Robin.
>
>>Signed-off-by: Peng Fan <van.freenix@...il.com>
>>Cc: Will Deacon <will.deacon@....com>
>>Cc: Robin Murphy <robin.murphy@....com>
>>---
>>
>>Hi Will,
>>
>>  Patch based on iommu/devel branch.
>>
>>
>>  drivers/iommu/arm-smmu.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>>
>>diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>>index acff332..d094a5a 100644
>>--- a/drivers/iommu/arm-smmu.c
>>+++ b/drivers/iommu/arm-smmu.c
>>@@ -98,6 +98,9 @@
>>  #define sCR0_BSU_SHIFT			14
>>  #define sCR0_BSU_MASK			0x3
>>
>>+/* Auxiliary Configuration register */
>>+#define ARM_SMMU_GR0_sACR		0x10
>>+
>>  /* Identification registers */
>>  #define ARM_SMMU_GR0_ID0		0x20
>>  #define ARM_SMMU_GR0_ID1		0x24
>>@@ -235,6 +238,8 @@
>>
>>  #define ARM_MMU500_ACTLR_CPRE		(1 << 1)
>>
>>+#define ARM_MMU500_ACR_CACHE_LOCK	(1 << 26)
>>+
>>  #define CB_PAR_F			(1 << 0)
>>
>>  #define ATSR_ACTIVE			(1 << 0)
>>@@ -1506,6 +1511,16 @@ static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
>>  		writel_relaxed(reg, gr0_base + ARM_SMMU_GR0_S2CR(i));
>>  	}
>>
>>+	/*
>>+	 * Before clearing ARM_MMU500_ACTLR_CPRE, need to
>>+	 * clear CACHE_LOCK bit of ACR first.
>>+	 */
>>+	if (smmu->model == ARM_MMU500) {
>>+		reg = readl_relaxed(gr0_base + ARM_SMMU_GR0_sACR);
>>+		reg &= ~ARM_MMU500_ACR_CACHE_LOCK;
>>+		writel_relaxed(reg, gr0_base + ARM_SMMU_GR0_sACR);
>>+	}
>>+
>>  	/* Make sure all context banks are disabled and clear CB_FSR  */
>>  	for (i = 0; i < smmu->num_context_banks; ++i) {
>>  		cb_base = ARM_SMMU_CB_BASE(smmu) + ARM_SMMU_CB(smmu, i);
>>
>