Re: [PATCH 0/6] firmware: qcom: scm: Fixes for concurrency

[neil.armstrong@linaro.org]

On 20/11/2024 12:13, Dmitry Baryshkov wrote:
> On Tue, Nov 19, 2024 at 07:33:16PM +0100, Krzysztof Kozlowski wrote:
>> SCM driver looks messy in terms of handling concurrency of probe.  The
>> driver exports interface which is guarded by global '__scm' variable
>> but:
>> 1. Lacks proper read barrier (commit adding write barriers mixed up
>>     READ_ONCE with a read barrier).
>> 2. Lacks barriers or checks for '__scm' in multiple places.
>> 3. Lacks probe error cleanup.
>>
>> I fixed here few visible things, but this was not tested extensively.  I
>> tried only SM8450.
>>
>> ARM32 and SC8280xp/X1E platforms would be useful for testing as well.
> 
> ARM32 devices are present in the lab.

I passed the patchset on our devices, and no regressions observed:

arm32: https://git.codelinaro.org/linaro/qcomlt/ci/staging/cdba-tester/-/pipelines/116195
arm64(including x1e): https://git.codelinaro.org/linaro/qcomlt/ci/staging/cdba-tester/-/pipelines/116201

Neil

> 
>>
>> All the issues here are non-urgent, IOW, they were here for some time
>> (v6.10-rc1 and earlier).
>>
>> Best regards,
>> Krzysztof
>>
>> ---
>> Krzysztof Kozlowski (6):
>>        firmware: qcom: scm: Fix missing read barrier in qcom_scm_is_available()
>>        firmware: qcom: scm: Fix missing read barrier in qcom_scm_get_tzmem_pool()
>>        firmware: qcom: scm: Handle various probe ordering for qcom_scm_assign_mem()
>>        [RFC/RFT] firmware: qcom: scm: Cleanup global '__scm' on probe failures
>>        firmware: qcom: scm: smc: Handle missing SCM device
>>        firmware: qcom: scm: smc: Narrow 'mempool' variable scope
>>
>>   drivers/firmware/qcom/qcom_scm-smc.c |  6 +++-
>>   drivers/firmware/qcom/qcom_scm.c     | 55 +++++++++++++++++++++++++-----------
>>   2 files changed, 44 insertions(+), 17 deletions(-)
>> ---
>> base-commit: 414c97c966b69e4a6ea7b32970fa166b2f9b9ef0
>> change-id: 20241119-qcom-scm-missing-barriers-and-all-sort-of-srap-a25d59074882
>>
>> Best regards,
>> -- 
>> Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>>
>