linux-kernel - Re: [PATCH v13 6/6] iommu/arm-smmu: add support for PRR bit setup

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Message-ID: <CAF6AEGv_9e-TDW1r0N4-db6pY_aV_EZFqrpNbATVS5Vy6+fs1g@mail.gmail.com>
Date: Fri, 28 Jun 2024 08:44:08 -0700
From: Rob Clark <robdclark@...il.com>
To: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
Cc: will@...nel.org, robin.murphy@....com, joro@...tes.org, jgg@...pe.ca, 
	jsnitsel@...hat.com, robh@...nel.org, krzysztof.kozlowski@...aro.org, 
	quic_c_gdjako@...cinc.com, dmitry.baryshkov@...aro.org, 
	konrad.dybcio@...aro.org, iommu@...ts.linux.dev, 
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 6/6] iommu/arm-smmu: add support for PRR bit setup

On Fri, Jun 28, 2024 at 8:10 AM Bibek Kumar Patro
<quic_bibekkum@...cinc.com> wrote:
>
>
>
> On 6/28/2024 7:47 PM, Rob Clark wrote:
> > On Fri, Jun 28, 2024 at 7:05 AM Bibek Kumar Patro
> > <quic_bibekkum@...cinc.com> wrote:
> >>
> >> Add an adreno-smmu-priv interface for drm/msm to call
> >> into arm-smmu-qcom and initiate the PRR bit setup or reset
> >> sequence as per request.
> >>
> >> This will be used by GPU to setup the PRR bit and related
> >> configuration registers through adreno-smmu private
> >> interface instead of directly poking the smmu hardware.
> >>
> >> Suggested-by: Rob Clark <robdclark@...il.com>
> >> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
> >> ---
> >>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 23 ++++++++++++++++++++++
> >>   drivers/iommu/arm/arm-smmu/arm-smmu.h      |  2 ++
> >>   include/linux/adreno-smmu-priv.h           |  6 +++++-
> >>   3 files changed, 30 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> >> index bd101a161d04..64571a1c47b8 100644
> >> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> >> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> >> @@ -28,6 +28,7 @@
> >>   #define PREFETCH_SHALLOW       (1 << PREFETCH_SHIFT)
> >>   #define PREFETCH_MODERATE      (2 << PREFETCH_SHIFT)
> >>   #define PREFETCH_DEEP          (3 << PREFETCH_SHIFT)
> >> +#define GFX_ACTLR_PRR          (1 << 5)
> >>
> >>   static const struct actlr_config sc7280_apps_actlr_cfg[] = {
> >>          { 0x0800, 0x04e0, PREFETCH_DEFAULT | CMTLB },
> >> @@ -235,6 +236,27 @@ static void qcom_adreno_smmu_resume_translation(const void *cookie, bool termina
> >>          arm_smmu_cb_write(smmu, cfg->cbndx, ARM_SMMU_CB_RESUME, reg);
> >>   }
> >>
> >> +static void qcom_adreno_smmu_set_prr(const void *cookie, phys_addr_t page_addr, bool set)
> >> +{
> >> +       struct arm_smmu_domain *smmu_domain = (void *)cookie;
> >> +       struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> >> +       struct arm_smmu_device *smmu = smmu_domain->smmu;
> >> +       u32 reg = 0;
> >> +
> >> +       writel_relaxed(lower_32_bits(page_addr),
> >> +                               smmu->base + ARM_SMMU_GFX_PRR_CFG_LADDR);
> >> +
> >> +       writel_relaxed(upper_32_bits(page_addr),
> >> +                               smmu->base + ARM_SMMU_GFX_PRR_CFG_UADDR);
> >> +
> >> +       reg =  arm_smmu_cb_read(smmu, cfg->cbndx, ARM_SMMU_CB_ACTLR);
> >> +       reg &= ~GFX_ACTLR_PRR;
> >> +       if (set)
> >> +               reg |= FIELD_PREP(GFX_ACTLR_PRR, 1);
> >> +       arm_smmu_cb_write(smmu, cfg->cbndx, ARM_SMMU_CB_ACTLR, reg);
> >> +
> >
> > nit, extra line
> >
>
> Ack, will remove this. Thanks for pointing out.
>
> > Also, if you passed a `struct page *` instead, then you could drop the
> > bool param, ie. passing NULL for the page would disable PRR.  But I
> > can go either way if others have a strong preference for phys_addr_t.
> >
>
> Oh okay, this looks simple to reset the prr bit.
> But since this page is allocated and is used inside gfx driver
> before being utilized for prr bit operation, would it be safe for
> drm/gfx driver to keep a reference to this page in smmu driver?
>
> Since we only need the page address for configuring the
> CFG_UADDR/CFG_LADDR registers so passed the phys_addr_t.

I don't think the smmu driver needs to keep a reference to the page..
we can just say it is the responsibility of the drm driver to call
set_prr(NULL) before freeing the page

BR,
-R

> > Otherwise, lgtm
> >
> > BR,
> > -R
> >
>
> Thanks & regards,
> Bibek
>
> >> +}
> >> +
> >>   #define QCOM_ADRENO_SMMU_GPU_SID 0
> >>
> >>   static bool qcom_adreno_smmu_is_gpu_device(struct device *dev)
> >> @@ -407,6 +429,7 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
> >>          priv->get_fault_info = qcom_adreno_smmu_get_fault_info;
> >>          priv->set_stall = qcom_adreno_smmu_set_stall;
> >>          priv->resume_translation = qcom_adreno_smmu_resume_translation;
> >> +       priv->set_prr = qcom_adreno_smmu_set_prr;
> >>
> >>          actlrvar = qsmmu->data->actlrvar;
> >>          if (!actlrvar)
> >> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> >> index d9c2ef8c1653..3076bef49e20 100644
> >> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> >> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> >> @@ -154,6 +154,8 @@ enum arm_smmu_cbar_type {
> >>   #define ARM_SMMU_SCTLR_M               BIT(0)
> >>
> >>   #define ARM_SMMU_CB_ACTLR              0x4
> >> +#define ARM_SMMU_GFX_PRR_CFG_LADDR     0x6008
> >> +#define ARM_SMMU_GFX_PRR_CFG_UADDR     0x600C
> >>
> >>   #define ARM_SMMU_CB_RESUME             0x8
> >>   #define ARM_SMMU_RESUME_TERMINATE      BIT(0)
> >> diff --git a/include/linux/adreno-smmu-priv.h b/include/linux/adreno-smmu-priv.h
> >> index c637e0997f6d..d6e2ca9f8d8c 100644
> >> --- a/include/linux/adreno-smmu-priv.h
> >> +++ b/include/linux/adreno-smmu-priv.h
> >> @@ -49,7 +49,10 @@ struct adreno_smmu_fault_info {
> >>    *                 before set_ttbr0_cfg().  If stalling on fault is enabled,
> >>    *                 the GPU driver must call resume_translation()
> >>    * @resume_translation: Resume translation after a fault
> >> - *
> >> + * @set_prr:      Extendible interface to be used by GPU to modify the
> >> + *                 ACTLR register bits, currently used to configure
> >> + *                 Partially-Resident-Region (PRR) feature's
> >> + *                 setup and reset sequence as requested.
> >>    *
> >>    * The GPU driver (drm/msm) and adreno-smmu work together for controlling
> >>    * the GPU's SMMU instance.  This is by necessity, as the GPU is directly
> >> @@ -67,6 +70,7 @@ struct adreno_smmu_priv {
> >>       void (*get_fault_info)(const void *cookie, struct adreno_smmu_fault_info *info);
> >>       void (*set_stall)(const void *cookie, bool enabled);
> >>       void (*resume_translation)(const void *cookie, bool terminate);
> >> +    void (*set_prr)(const void *cookie, phys_addr_t page_addr, bool set);
> >>   };
> >>
> >>   #endif /* __ADRENO_SMMU_PRIV_H */
> >> --
> >> 2.34.1
> >>