lkml.org 
[lkml]   [2018]   [Aug]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[PATCH 0/5] Qcom smmu-500 TLB invalidation errata for sdm845
Date
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

\
 
 \ /
  Last update: 2018-08-14 12:56    [W:0.150 / U:0.436 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site