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SubjectRe: [PATCH v18 2/4] iommu/arm-smmu: Add a way for implementations to influence SCTLR
On Mon 02 Nov 12:18 CST 2020, Robin Murphy wrote:

> On 2020-11-02 17:14, Jordan Crouse wrote:
> > From: Rob Clark <robdclark@chromium.org>
> >
> > For the Adreno GPU's SMMU, we want SCTLR.HUPCF set to ensure that
> > pending translations are not terminated on iova fault. Otherwise
> > a terminated CP read could hang the GPU by returning invalid
> > command-stream data.
> >
> > Signed-off-by: Rob Clark <robdclark@chromium.org>
> > Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> > Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> > ---
> >
> > drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 6 ++++++
> > drivers/iommu/arm/arm-smmu/arm-smmu.c | 3 +++
> > drivers/iommu/arm/arm-smmu/arm-smmu.h | 3 +++
> > 3 files changed, 12 insertions(+)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> > index 1e942eed2dfc..0663d7d26908 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> > @@ -129,6 +129,12 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
> > (smmu_domain->cfg.fmt == ARM_SMMU_CTX_FMT_AARCH64))
> > pgtbl_cfg->quirks |= IO_PGTABLE_QUIRK_ARM_TTBR1;
> > + /*
> > + * On the GPU device we want to process subsequent transactions after a
> > + * fault to keep the GPU from hanging
> > + */
> > + smmu_domain->cfg.sctlr_set |= ARM_SMMU_SCTLR_HUPCF;
> > +
> > /*
> > * Initialize private interface with GPU:
> > */
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > index dad7fa86fbd4..1f06ab219819 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > @@ -617,6 +617,9 @@ void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
> > if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
> > reg |= ARM_SMMU_SCTLR_E;
> > + reg |= cfg->sctlr_set;
> > + reg &= ~cfg->sctlr_clr;
>
> Since we now have a write_s2cr hook, I'm inclined to think that the
> consistency of a write_sctlr hook that could similarly apply its own
> arbitrary tweaks would make sense for this. Does anyone have any strong
> opinions?
>

I like it.

Regards,
Bjorn

> Robin.
>
> > +
> > arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, reg);
> > }
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> > index 6c5ff9999eae..ddf2ca4c923d 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> > @@ -144,6 +144,7 @@ enum arm_smmu_cbar_type {
> > #define ARM_SMMU_CB_SCTLR 0x0
> > #define ARM_SMMU_SCTLR_S1_ASIDPNE BIT(12)
> > #define ARM_SMMU_SCTLR_CFCFG BIT(7)
> > +#define ARM_SMMU_SCTLR_HUPCF BIT(8)
> > #define ARM_SMMU_SCTLR_CFIE BIT(6)
> > #define ARM_SMMU_SCTLR_CFRE BIT(5)
> > #define ARM_SMMU_SCTLR_E BIT(4)
> > @@ -341,6 +342,8 @@ struct arm_smmu_cfg {
> > u16 asid;
> > u16 vmid;
> > };
> > + u32 sctlr_set; /* extra bits to set in SCTLR */
> > + u32 sctlr_clr; /* bits to mask in SCTLR */
> > enum arm_smmu_cbar_type cbar;
> > enum arm_smmu_context_fmt fmt;
> > };
> >

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