Re: [PATCH v2 09/10] drivers: qcom: rpmh: add support for batch RPMH request
From: Evan Green
Date: Wed Feb 21 2018 - 18:25:41 EST
Hello Lina,
On Thu, Feb 15, 2018 at 9:35 AM, Lina Iyer <ilina@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
> ---
> 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.
> @@ -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.
-Evan