Subject: [PATCH 8/8] iommu/arm-smmu: suppress fault information about CMD_PREFETCH_CONFIG execution

From: [email-masked] (leizhen)
Date: Tue, 30 Jun 2015 17:18:29 +0800

On 2015/6/30 1:49, Will Deacon wrote:
> On Fri, Jun 26, 2015 at 09:33:04AM +0100, Zhen Lei wrote:
>> Some broken SMMUv3 devices treat CMD_PREFETCH_CONFIG as illegal command,
>> it's ugly to print error information. CMD_PREFETCH_CONFIG is just used to
>> prefetch the configuration for a specified StreamID, without this command
>> will not impact SMMUv3 function.
>>
>> Signed-off-by: Zhen Lei <[email-masked]>
>> ---
>>  drivers/iommu/arm-smmu-v3.c | 18 ++++++++++++++----
>>  1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
>> index d799feb..3971aef 100644
>> --- a/drivers/iommu/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm-smmu-v3.c
>> @@ -813,6 +813,7 @@ static void arm_smmu_cmdq_skip_err(struct arm_smmu_device *smmu)
>>  	};
>>
>>  	int i;
>> +	u32 opcode;
>>  	u64 cmd[CMDQ_ENT_DWORDS];
>>  	struct arm_smmu_queue *q = &smmu->cmdq.q;
>>  	u32 cons = readl_relaxed(q->cons_reg);
>> @@ -821,15 +822,14 @@ static void arm_smmu_cmdq_skip_err(struct arm_smmu_device *smmu)
>>  		.opcode = CMDQ_OP_CMD_SYNC,
>>  	};
>>
>> -	dev_err(smmu->dev, "CMDQ error (cons 0x%08x): %s\n", cons,
>> -		cerror_str[idx]);
>> -
>>  	switch (idx) {
>>  	case CMDQ_ERR_CERROR_ILL_IDX:
>>  		break;
>>  	case CMDQ_ERR_CERROR_ABT_IDX:
>> -		dev_err(smmu->dev, "retrying command fetch\n");
>>  	case CMDQ_ERR_CERROR_NONE_IDX:
>> +		dev_err(smmu->dev, "CMDQ error (cons 0x%08x): %s\n", cons,
>> +			cerror_str[idx]);
>> +		dev_err(smmu->dev, "retrying command execution\n");
> 
> Why are you making this (unrelated) change?
> 
> Out of interest, did the gerror code manage to turn the prefetch into
> a SYNC, as intended?

Yes, It worked fine. The program can continue to run normally, that's why I don't want to
print these error information. Because this problem is known on my platform, and can sliently
ignored.

> 
>>  		return;
>>  	}
>>
>> @@ -838,10 +838,20 @@ static void arm_smmu_cmdq_skip_err(struct arm_smmu_device *smmu)
>>  	 * not to touch any of the shadow cmdq state.
>>  	 */
>>  	queue_read(cmd, Q_ENT(q, idx), q->ent_dwords);
>> +
>> +	/*
>> +	 * Some broken SMMUv3 devices treat CMD_PREFETCH_CONFIG as illegal
>> +	 * command, it's ugly to print error information.
>> +	 */
>> +	opcode = (cmd[0] >> CMDQ_0_OP_SHIFT) & CMDQ_0_OP_MASK;
>> +	if (opcode == CMDQ_OP_PREFETCH_CFG)
>> +		goto skip_error_command;
>> +
> 
> I think a better way to fix this would be to add a quick to the device-tree
> along the lines of "hisilicon,broken-prefetch-cmd" which we could check
> before issuing the prefetch command in arm_smmu_write_strtab_ent.
> 
> Something along the lines of the arm_smmu_options in arm-smmu.c would be
> a good basis for quirks.

It's a good idea. I known the arm_smmu_options, I will rewrite this patch in V2.

> Will
> .