[PATCHv6 0/3] QCOM smmu-500 wait-for-safe handling for sdm845

Sai Prakash Ranjan
2019-09-17T09:45:20Z

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
devices.
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 v5:
* Addressed Robin's comments and removed unwanted header file.

Changes since v4:
* Addressed Stephen's comments.
* Moved QCOM specific implementation to arm-smmu-qcom.c as per Robin's suggestion.

Changes since v3:
* Based on arm-smmu implementation cleanup series [5] by Robin Murphy which is
already merged in Will's tree [6].
* Implemented the sdm845 specific reset hook which does arm_smmu_device_reset()
followed by making SCM call to disable the wait-for-safe logic.
* Removed depedency for SCM call on any dt flag. We invariably try to disable
the wait-for-safe logic on sdm845. The platforms such as mtp845, and db845
that implement handlers for this particular SCM call should be able disable
wait-for-safe logic.
Other platforms such as cheza don't enable the wait-for-safe logic at all
from their bootloaders. So there's no need to disable the same.
* No change in SCM call patches 1 & 2.

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/1127798/
[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
[5] https://patchwork.kernel.org/patch/11096265/
[6] https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/

Vivek Gautam (3):
firmware: qcom_scm-64: Add atomic version of qcom_scm_call
firmware/qcom_scm: Add scm call to handle smmu errata
iommu: arm-smmu-impl: Add sdm845 implementation hook

drivers/firmware/qcom_scm-32.c | 5 ++
drivers/firmware/qcom_scm-64.c | 152 +++++++++++++++++++++++----------
drivers/firmware/qcom_scm.c | 6 ++
drivers/firmware/qcom_scm.h | 5 ++
drivers/iommu/Makefile | 2 +-
drivers/iommu/arm-smmu-impl.c | 6 +-
drivers/iommu/arm-smmu-qcom.c | 51 +++++++++++
drivers/iommu/arm-smmu.h | 3 +
include/linux/qcom_scm.h | 2 +
9 files changed, 185 insertions(+), 47 deletions(-)
create mode 100644 drivers/iommu/arm-smmu-qcom.c

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