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

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Message-ID: <CA+sq2CdR0vC76F1m-LvYGfZW32nKbQg9dQsfJ_jtvYgZ7yyt3g@mail.gmail.com>
Date:   Wed, 3 May 2017 18:49:09 +0530
From:   Sunil Kovvuri <sunil.kovvuri@...il.com>
To:     Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        LAKML <linux-arm-kernel@...ts.infradead.org>,
        Robert Richter <robert.richter@...ium.com>, jcm@...hat.com,
        Sunil Goutham <sgoutham@...ium.com>, Geetha <gakula@...ium.com>
Subject: Re: [PATCH] iommu/arm-smmu-v3: Poll for CMDQ drain completion more effectively

On Thu, Apr 27, 2017 at 4:43 PM,  <sunil.kovvuri@...il.com> wrote:
> From: Sunil Goutham <sgoutham@...ium.com>
>
> 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@...ium.com>
> Signed-off-by: Geetha <gakula@...ium.com>
> ---
>  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.