Hi Robin,


On 8/14/2018 10:29 PM, Robin Murphy wrote:

On 14/08/18 11:55, Vivek Gautam wrote:

quoted

Cleanup to re-use some of the stuff

Signed-off-by: Vivek Gautam <redacted>
---
? 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.

quoted

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.

quoted

? /*
?? * 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