linux-kernel - Re: [PATCH v9 4/6] iommu/arm-smmu-v3: Add CS_NONE quirk for CONFIG_TEGRA241

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Message-ID: <ZoREzIAqzyamQBWL@Asurada-Nvidia>
Date: Tue, 2 Jul 2024 11:19:56 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Will Deacon <will@...nel.org>
CC: <robin.murphy@....com>, <joro@...tes.org>, <jgg@...dia.com>,
	<thierry.reding@...il.com>, <vdumpa@...dia.com>, <jonathanh@...dia.com>,
	<linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v9 4/6] iommu/arm-smmu-v3: Add CS_NONE quirk for
 CONFIG_TEGRA241_CMDQV

Hi Will,

On Tue, Jul 02, 2024 at 06:43:07PM +0100, Will Deacon wrote:
> On Wed, Jun 12, 2024 at 02:45:31PM -0700, Nicolin Chen wrote:
> > The CMDQV extension in NVIDIA Tegra241 SoC only supports CS_NONE in the
> > CS field of CMD_SYNC. Add a quirk flag to accommodate that.
> >
> > Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> > Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> > ---
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 +++++++-
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 3 +++
> >  2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > index c864c634cd23..ba0e24d5ffbf 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> > @@ -345,6 +345,11 @@ static void arm_smmu_cmdq_build_sync_cmd(u64 *cmd, struct arm_smmu_device *smmu,
> >                FIELD_PREP(CMDQ_SYNC_0_MSH, ARM_SMMU_SH_ISH) |
> >                FIELD_PREP(CMDQ_SYNC_0_MSIATTR, ARM_SMMU_MEMATTR_OIWB);
> >
> > +     if (q->quirks & CMDQ_QUIRK_SYNC_CS_NONE_ONLY) {
> > +             cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_NONE);
> > +             return;
> > +     }
> > +
> >       if (!(smmu->options & ARM_SMMU_OPT_MSIPOLL)) {
> >               cmd[0] |= FIELD_PREP(CMDQ_SYNC_0_CS, CMDQ_SYNC_0_CS_SEV);
> >               return;
> > @@ -690,7 +695,8 @@ static int arm_smmu_cmdq_poll_until_sync(struct arm_smmu_device *smmu,
> >                                        struct arm_smmu_cmdq *cmdq,
> >                                        struct arm_smmu_ll_queue *llq)
> >  {
> > -     if (smmu->options & ARM_SMMU_OPT_MSIPOLL)
> > +     if (smmu->options & ARM_SMMU_OPT_MSIPOLL &&
> > +         !(cmdq->q.quirks & CMDQ_QUIRK_SYNC_CS_NONE_ONLY))
> >               return __arm_smmu_cmdq_poll_until_msi(smmu, cmdq, llq);
> >
> >       return __arm_smmu_cmdq_poll_until_consumed(smmu, cmdq, llq);
> > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > index 180c0b1e0658..01227c0de290 100644
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> > @@ -543,6 +543,9 @@ struct arm_smmu_queue {
> >
> >       u32 __iomem                     *prod_reg;
> >       u32 __iomem                     *cons_reg;
> > +
> > +#define CMDQ_QUIRK_SYNC_CS_NONE_ONLY BIT(0)  /* CMD_SYNC CS field supports CS_NONE only */
> > +     u32                             quirks;
> 
> Please can you use the existing smmu->options field instead of adding
> another place to track quirks? Or do you need this only for some of the
> queues for a given SMMU device?

VCMDQs are extension of a regular SMMU (with its own CMDQ). So,
SMMU CMDQ still supports SIG_IRQ for the CS field, while VCMDQs
could only support SIG_NONE. In another word, this quirk is not
per SMMU but per Queue.

I can highlight this in the commit message, if that would make
it clear.

Thanks
Nicolin