[PATCH v2 0/4] Qcom smmu-500 TLB invalidation errata for sdm845
vivek.gautam at codeaurora.org
Mon Sep 10 03:38:36 PDT 2018
On 09/10/2018 11:55 AM, Vivek Gautam wrote:
> Qcom's implementation of arm,mmu-500 on sdm845 has a functional/performance
> errata  because of which the TCU cache look ups are stalled during
> invalidation cycle. This is mitigated by serializing all the invalidation
> requests coming to the smmu.
> This patch series addresses this errata by adding new tlb_ops for
> qcom,sdm845-smmu-500 . These ops take context bank locks for all the
> tlb_ops that queue and sync the TLB invalidation requests.
> Besides adding locks, there's a way to expadite these TLB invalidations
> for display and camera devices by turning off the 'wait-for-safe' logic
> in hardware that holds the tlb invalidations until a safe level.
> This 'wait-for-safe' logic is controlled by toggling a chicken bit
> through a secure register. This secure register is accessed by making an
> explicit SCM call into the EL3 firmware.
> There are two ways of handling this logic -
> * Firmware, such as tz present on sdm845-mtp devices has a handler to do
> all the register access and bit set/clear. So is the handling in
> downstream arm-smmu driver .
> * Other firmwares can have handlers to just read/write this secure
> register. In such cases the kernel make io_read/writel scm calls to
> modify the register.
> This patch series adds APIs in qcom-scm driver to handle both of these
> Lastly, since these TLB invalidations can happen in atomic contexts
> there's a need to add atomic versions of qcom_scm_io_readl/writel() and
> qcom_scm_call() APIs. The traditional scm calls take mutex and we therefore
> can't use these calls in atomic contexts.
> This patch series is adapted version of how the errata is handled in
> downstream .
> Changes since v1:
> * Addressed Will and Robin's comments:
> - Dropped the patch that forked out __arm_smmu_tlb_inv_range_nosync(),
> and __arm_smmu_tlb_sync().
> - Cleaned up the errata patch further to use downstream polling mechanism
> for tlb sync.
> * No change in SCM call patches - patches 1 to 3.
>  https://source.codeaurora.org/quic/la/kernel/msm-4.9/tree/drivers/iommu/arm-smmu.c?h=msm-4.9#n4842
>  https://lore.kernel.org/patchwork/patch/974114/
>  https://source.codeaurora.org/quic/la/kernel/msm-4.9/tree/drivers/iommu/arm-smmu.c?h=msm-4.9#n4864
>  https://patchwork.kernel.org/patch/10565349/
> Vivek Gautam (4):
> firmware: qcom_scm-64: Add atomic version of qcom_scm_call
> firmware/qcom_scm: Add atomic version of io read/write APIs
> firmware/qcom_scm: Add scm call to handle smmu errata
> iommu/arm-smmu: Add support to handle Qcom's TLBI serialization errata
> drivers/firmware/qcom_scm-32.c | 17 ++++
> drivers/firmware/qcom_scm-64.c | 181 +++++++++++++++++++++++++++++++----------
> drivers/firmware/qcom_scm.c | 18 ++++
> drivers/firmware/qcom_scm.h | 9 ++
> drivers/iommu/arm-smmu-regs.h | 2 +
> drivers/iommu/arm-smmu.c | 133 +++++++++++++++++++++++++++++-
> include/linux/qcom_scm.h | 6 ++
> 7 files changed, 320 insertions(+), 46 deletions(-)
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