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SubjectRe: [PATCHv2] iommu/arm-smmu-qcom: Add debug support for TLB sync timeouts
On Thu, May 26, 2022 at 09:44:03AM +0530, Sai Prakash Ranjan wrote:
> TLB sync timeouts can be due to various reasons such as TBU power down
> or pending TCU/TBU invalidation/sync and so on. Debugging these often
> require dumping of some implementation defined registers to know the
> status of TBU/TCU operations and some of these registers are not
> accessible in non-secure world such as from kernel and requires SMC
> calls to read them in the secure world. So, add this debug support
> to dump implementation defined registers for TLB sync timeout issues.
>
> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com>
> ---
>
> Changes in v2:
> * Use scm call consistently so that it works on older chipsets where
> some of these regs are secure registers.
> * Add device specific data to get the implementation defined register
> offsets.
>
> ---
> drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 161 ++++++++++++++++++---
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 2 +
> drivers/iommu/arm/arm-smmu/arm-smmu.h | 1 +
> 3 files changed, 146 insertions(+), 18 deletions(-)

If this is useful to you, then I suppose it's something we could support,
however I'm pretty worried about our ability to maintain/scale this stuff
as it is extended to support additional SoCs and other custom debugging
features.

Perhaps you could stick it all in arm-smmu-qcom-debug.c and have a new
config option for that, so at least it's even further out of the way?

Will

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