[v3,0/4] Qcom smmu-500 wait-for-safe handling for sdm845
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Message ID 20190612071554.13573-1-vivek.gautam@codeaurora.org
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  • Qcom smmu-500 wait-for-safe handling for sdm845
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Vivek Gautam June 12, 2019, 7:15 a.m. UTC
Subject changed, older subject was -
Qcom smmu-500 TLB invalidation errata for sdm845.
Previous version of the patches are at [1]:

Qcom's implementation of smmu-500 on sdm845 adds a hardware logic called
wait-for-safe. This logic helps in meeting the invalidation requirements
from 'real-time clients', such as display and camera. This wait-for-safe
logic ensures that the invalidations happen after getting an ack from these
In this patch-series we are disabling this wait-for-safe logic from the
arm-smmu driver's probe as with this enabled the hardware tries to
throttle invalidations from 'non-real-time clients', such as USB and UFS.

For detailed information please refer to patch [3/4] in this series.
I have included the device tree patch too in this series for someone who
would like to test out this. Here's a branch [2] that gets display on MTP
SDM845 device.

This patch series is inspired from downstream work to handle under-performance
issues on real-time clients on sdm845. In downstream we add separate page table
ops to handle TLB maintenance and toggle wait-for-safe in tlb_sync call so that
achieve required performance for display and camera [3, 4].

Changes since v2:
 * Dropped the patch to add atomic io_read/write scm API.
 * Removed support for any separate page table ops to handle wait-for-safe.
   Currently just disabling this wait-for-safe logic from arm_smmu_device_probe()
   to achieve performance on USB/UFS on sdm845.
 * Added a device tree patch to add smmu option for fw-implemented support
   for SCM call to take care of SAFE toggling.

Changes since v1:
 * Addressed Will and Robin's comments:
    - Dropped the patch[4] 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.

[1] https://lore.kernel.org/patchwork/cover/983913/
[2] https://github.com/vivekgautam1/linux/tree/v5.2-rc4/sdm845-display-working
[3] https://source.codeaurora.org/quic/la/kernel/msm-4.9/commit/drivers/iommu/arm-smmu.c?h=CogSystems-msm-49/msm-4.9&id=da765c6c75266b38191b38ef086274943f353ea7
[4] https://source.codeaurora.org/quic/la/kernel/msm-4.9/commit/drivers/iommu/arm-smmu.c?h=CogSystems-msm-49/msm-4.9&id=8696005aaaf745de68f57793c1a534a34345c30a

Vivek Gautam (4):
  firmware: qcom_scm-64: Add atomic version of qcom_scm_call
  firmware/qcom_scm: Add scm call to handle smmu errata
  iommu/arm-smmu: Add support to handle Qcom's wait-for-safe logic
  arm64: dts/sdm845: Enable FW implemented safe sequence handler on MTP

 arch/arm64/boot/dts/qcom/sdm845.dtsi |   1 +
 drivers/firmware/qcom_scm-32.c       |   5 ++
 drivers/firmware/qcom_scm-64.c       | 149 ++++++++++++++++++++++++-----------
 drivers/firmware/qcom_scm.c          |   6 ++
 drivers/firmware/qcom_scm.h          |   5 ++
 drivers/iommu/arm-smmu.c             |  16 ++++
 include/linux/qcom_scm.h             |   2 +
 7 files changed, 140 insertions(+), 44 deletions(-)