Qcom's implementation of arm,mmu-500 on sdm845 has a functional/performance errata [1] 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 [2]. 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 [3]. * 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 cases. 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 [1]. [1] https://source.codeaurora.org/quic/la/kernel/msm-4.9/tree/drivers/iommu/arm-smmu.c?h=msm-4.9#n4842 [2] https://lore.kernel.org/patchwork/patch/974114/ [3] https://source.codeaurora.org/quic/la/kernel/msm-4.9/tree/drivers/iommu/arm-smmu.c?h=msm-4.9#n4864 Vivek Gautam (5): 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: Make way to add Qcom's smmu-500 errata handling 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 | 168 ++++++++++++++++++++++++++++++++++++-- include/linux/qcom_scm.h | 6 ++ 7 files changed, 348 insertions(+), 53 deletions(-) -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
