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SubjectRe: [PATCH v2 09/10] drivers: qcom: rpmh: add support for batch RPMH request
On Wed, Feb 21 2018 at 23:25 +0000, Evan Green wrote:
>Hello Lina,
>
>On Thu, Feb 15, 2018 at 9:35 AM, Lina Iyer <ilina@codeaurora.org> wrote:
>> Platform drivers need make a lot of resource state requests at the same
>> time, say, at the start or end of an usecase. It can be quite
>> inefficient to send each request separately. Instead they can give the
>> RPMH library a batch of requests to be sent and wait on the whole
>> transaction to be complete.
>>
>> rpmh_write_batch() is a blocking call that can be used to send multiple
>> RPMH command sets. Each RPMH command set is set asynchronously and the
>> API blocks until all the command sets are complete and receive their
>> tx_done callbacks.
>>
>> Signed-off-by: Lina Iyer <ilina@codeaurora.org>
>> ---
>> drivers/soc/qcom/rpmh.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++++
>> include/soc/qcom/rpmh.h | 8 +++
>> 2 files changed, 158 insertions(+)
>>
>> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
>> index dff4c46be3af..6f60bb9a4dfa 100644
>> --- a/drivers/soc/qcom/rpmh.c
>> +++ b/drivers/soc/qcom/rpmh.c
>[...]
>> @@ -394,6 +537,11 @@ int rpmh_flush(struct rpmh_client *rc)
>> }
>> spin_unlock_irqrestore(&rpm->lock, flags);
>>
>> + /* First flush the cached batch requests */
>> + ret = flush_batch(rc);
>> + if (ret)
>> + return ret;
>> +
>> /*
>> * Nobody else should be calling this function other than system PM,,
>> * hence we can run without locks.
This comment and the comment in the header of this function.

>> @@ -438,6 +586,8 @@ int rpmh_invalidate(struct rpmh_client *rc)
>> if (IS_ERR_OR_NULL(rc))
>> return -EINVAL;
>>
>> + invalidate_batch(rc);
>> +
>
>Similarly to my comments in patch 7, aren't there races here with
>adding new elements? After flush_batch, but before invalidate_batch,
>somebody could call cache_batch, which would add new things on the end
>of the array. These new items would be clobbered by invalidate_batch,
>without having been flushed first.
>
Flush is a system PM function and is not called by drivers and is not
expected to run conncurrently with other threads using the RPMH library.

Thanks,
Lina

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