[PATCH 4/5] iommu/arm-smmu: Make way to add Qcom's smmu-500 errata handling

[vivek.gautam@codeaurora.org (Vivek Gautam)]

Hi Robin,


On 8/14/2018 10:29 PM, Robin Murphy wrote:
> On 14/08/18 11:55, Vivek Gautam wrote:
>> Cleanup to re-use some of the stuff
>>
>> Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
>> ---
>> ? drivers/iommu/arm-smmu.c | 32 +++++++++++++++++++++++++-------
>> ? 1 file changed, 25 insertions(+), 7 deletions(-)
>
> I think the overall diffstat would be an awful lot smaller if the 
> erratum workaround just has its own readl_poll_timeout() as it does in 
> the vendor kernel. The burst-polling loop is for minimising latency in 
> high-throughput situations, and if you're in a workaround which has to 
> lock *every* register write and issue two firmware calls around each 
> sync I think you're already well out of that game.

Sorry for the delayed response. I was on vacation.
I will fix this in my next version by adding the separate 
read_poll_timeout() for the erratum WA.

>
>> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>> index 32e86df80428..75c146751c87 100644
>> --- a/drivers/iommu/arm-smmu.c
>> +++ b/drivers/iommu/arm-smmu.c
>> @@ -391,21 +391,31 @@ static void __arm_smmu_free_bitmap(unsigned 
>> long *map, int idx)
>> ????? clear_bit(idx, map);
>> ? }
>> ? -/* Wait for any pending TLB invalidations to complete */
>> -static void __arm_smmu_tlb_sync(struct arm_smmu_device *smmu,
>> -??????????????? void __iomem *sync, void __iomem *status)
>> +static int __arm_smmu_tlb_sync_wait(void __iomem *status)
>> ? {
>> ????? unsigned int spin_cnt, delay;
>> ? -??? writel_relaxed(0, sync);
>> ????? for (delay = 1; delay < TLB_LOOP_TIMEOUT; delay *= 2) {
>> ????????? for (spin_cnt = TLB_SPIN_COUNT; spin_cnt > 0; spin_cnt--) {
>> ????????????? if (!(readl_relaxed(status) & sTLBGSTATUS_GSACTIVE))
>> -??????????????? return;
>> +??????????????? return 0;
>> ????????????? cpu_relax();
>> ????????? }
>> ????????? udelay(delay);
>> ????? }
>> +
>> +??? return -EBUSY;
>> +}
>> +
>> +/* Wait for any pending TLB invalidations to complete */
>> +static void __arm_smmu_tlb_sync(struct arm_smmu_device *smmu,
>> +??????????????? void __iomem *sync, void __iomem *status)
>> +{
>> +??? writel_relaxed(0, sync);
>> +
>> +??? if (!__arm_smmu_tlb_sync_wait(status))
>> +??????? return;
>> +
>> ????? dev_err_ratelimited(smmu->dev,
>> ????????????????? "TLB sync timed out -- SMMU may be deadlocked\n");
>> ? }
>> @@ -461,8 +471,9 @@ static void arm_smmu_tlb_inv_context_s2(void 
>> *cookie)
>> ????? arm_smmu_tlb_sync_global(smmu);
>> ? }
>> ? -static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, 
>> size_t size,
>> -????????????????????? size_t granule, bool leaf, void *cookie)
>> +static void __arm_smmu_tlb_inv_range_nosync(unsigned long iova, 
>> size_t size,
>> +??????????????????????? size_t granule, bool leaf,
>> +??????????????????????? void *cookie)
>> ? {
>> ????? struct arm_smmu_domain *smmu_domain = cookie;
>> ????? struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
>> @@ -498,6 +509,13 @@ static void 
>> arm_smmu_tlb_inv_range_nosync(unsigned long iova, size_t size,
>> ????? }
>> ? }
>> ? +static void arm_smmu_tlb_inv_range_nosync(unsigned long iova, 
>> size_t size,
>> +????????????????????? size_t granule, bool leaf,
>> +????????????????????? void *cookie)
>> +{
>> +??? __arm_smmu_tlb_inv_range_nosync(iova, size, granule, leaf, cookie);
>> +}
>> +
>
> AFAICS even after patch #5 this does absolutely nothing except make 
> the code needlessly harder to read :(

Sure, I will rather call arm_smmu_tlb_inv_range_nosync() from
qcom_errata_tlb_inv_range_nosync() then make this change.
Thanks for the review.

Best regards
Vivek

>
> Robin.
>
>> ? /*
>> ?? * On MMU-401 at least, the cost of firing off multiple TLBIVMIDs 
>> appears
>> ?? * almost negligible, but the benefit of getting the first one in 
>> as far ahead
>>