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

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Message-ID: <CA+sq2Cd0ii_U8jE7_yYOy+N+PeuAbd8-UCqV78u=Q5aKFhifmg@mail.gmail.com>
Date:   Wed, 3 May 2017 21:54:21 +0530
From:   Sunil Kovvuri <sunil.kovvuri@...il.com>
To:     Will Deacon <will.deacon@....com>
Cc:     Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org,
        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 Wed, May 3, 2017 at 9:29 PM, Will Deacon <will.deacon@....com> wrote:
> On Wed, May 03, 2017 at 09:24:13PM +0530, Sunil Kovvuri wrote:
>> On Wed, May 3, 2017 at 9:07 PM, Will Deacon <will.deacon@....com> wrote:
>> > On Wed, May 03, 2017 at 06:49:09PM +0530, Sunil Kovvuri wrote:
>> >> 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 ?
>> >
>> > Please be patient: the merge window is open and it's not been long since you
>> > posted the patch, which looks pretty bonkers at first glance.
>> >
>> > Will
>>
>> Look at this
>> https://lkml.org/lkml/2017/4/3/605
>> The same thing, i pinged after a week and you said you already picked it up.
>> All I am asking is how do i know the current status, how many days
>> would normally
>> be considered being patient ?
>
> At least wait until the merge window is over if it's not a fix, or keep an
> eye on the relevant branches (see below).
>
>> Instead of troubling you, is there a patchwork where i can check the status ?
>
> No, but I pick patches up on my iommu/devel branch here:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/
>
> and at some point they appear on for-joerg/arm-smmu/updates, which I send
> to Joerg (who is the iommu maintainer). He then puts them into linux-next
> before they get sent for inclusion in mainline during the next merge window.
>
> Will

Thanks for the info.

Sunil.