Re: [PATCH] iommu/arm-smmu-v3: Poll for CMDQ drain completion more effectively

From: Sunil Kovvuri
Date: Wed May 03 2017 - 09:19:22 EST


On Thu, Apr 27, 2017 at 4:43 PM, <sunil.kovvuri@xxxxxxxxx> wrote:
> From: Sunil Goutham <sgoutham@xxxxxxxxxx>
>
> Modified polling on CMDQ consumer similar to how polling is done for TLB SYNC
> completion in SMMUv2 driver. Code changes are done with reference to
>
> 8513c8930069 iommu/arm-smmu: Poll for TLB sync completion more effectively
>
> Poll timeout has been increased which addresses issue of 100us timeout not
> sufficient, when command queue is full with TLB invalidation commands.
>
> Signed-off-by: Sunil Goutham <sgoutham@xxxxxxxxxx>
> Signed-off-by: Geetha <gakula@xxxxxxxxxx>
> ---
> drivers/iommu/arm-smmu-v3.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index d412bdd..34599d4 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -379,6 +379,9 @@
> #define CMDQ_SYNC_0_CS_NONE (0UL << CMDQ_SYNC_0_CS_SHIFT)
> #define CMDQ_SYNC_0_CS_SEV (2UL << CMDQ_SYNC_0_CS_SHIFT)
>
> +#define CMDQ_DRAIN_TIMEOUT_US 1000
> +#define CMDQ_SPIN_COUNT 10
> +
> /* Event queue */
> #define EVTQ_ENT_DWORDS 4
> #define EVTQ_MAX_SZ_SHIFT 7
> @@ -737,7 +740,8 @@ static void queue_inc_prod(struct arm_smmu_queue *q)
> */
> static int queue_poll_cons(struct arm_smmu_queue *q, bool drain, bool wfe)
> {
> - ktime_t timeout = ktime_add_us(ktime_get(), ARM_SMMU_POLL_TIMEOUT_US);
> + ktime_t timeout = ktime_add_us(ktime_get(), CMDQ_DRAIN_TIMEOUT_US);
> + unsigned int spin_cnt, delay = 1;
>
> while (queue_sync_cons(q), (drain ? !queue_empty(q) : queue_full(q))) {
> if (ktime_compare(ktime_get(), timeout) > 0)
> @@ -746,8 +750,13 @@ static int queue_poll_cons(struct arm_smmu_queue *q, bool drain, bool wfe)
> if (wfe) {
> wfe();
> } else {
> - cpu_relax();
> - udelay(1);
> + for (spin_cnt = 0;
> + spin_cnt < CMDQ_SPIN_COUNT; spin_cnt++) {
> + cpu_relax();
> + continue;
> + }
> + udelay(delay);
> + delay *= 2;
> }
> }
>
> --
> 2.7.4
>

Sorry for the ignorance.
Is there a patchwork where I can check current status of ARM IOMMU
related patches ?

And is this patch accepted, if not any comments / feedback ?

Thanks,
Sunil.