linux-kernel - Re: [PATCH v8 09/10] drivers: qcom: rpmh: add support for batch RPMH request

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Date:   Wed, 9 May 2018 15:03:04 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Lina Iyer <ilina@...eaurora.org>
Cc:     andy.gross@...aro.org, david.brown@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        rnayak@...eaurora.org, bjorn.andersson@...aro.org,
        linux-kernel@...r.kernel.org, sboyd@...nel.org,
        evgreen@...omium.org, dianders@...omium.org, rplsssn@...eaurora.org
Subject: Re: [PATCH v8 09/10] drivers: qcom: rpmh: add support for batch RPMH
 request

On Wed, May 09, 2018 at 11:01:58AM -0600, Lina Iyer 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@...eaurora.org>
> ---
> 
> Changes in v7:
> 	- Check for loop out of bounds
> 
> Changes in v6:
> 	- replace rpmh_client with device *
> Changes in v4:
> 	- reorganize rpmh_write_batch()
> 	- introduce wait_count here, instead of patch#4
> ---
>  drivers/soc/qcom/rpmh.c | 154 +++++++++++++++++++++++++++++++++++++++-
>  include/soc/qcom/rpmh.h |   8 +++
>  2 files changed, 160 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> index 1bb62876795c..a0e277b4b846 100644
> --- a/drivers/soc/qcom/rpmh.c
> +++ b/drivers/soc/qcom/rpmh.c
>
> ...
>
> +static int flush_batch(struct rpmh_ctrlr *ctrlr)
> +{
> +	const struct rpmh_request *rpm_msg;
> +	unsigned long flags;
> +	int ret = 0;
> +	int i;
> +
> +	/* Send Sleep/Wake requests to the controller, expect no response */
> +	spin_lock_irqsave(&ctrlr->lock, flags);
> +	for (i = 0; ctrlr->batch_cache[i]; i++) {

I missed this earlier: the loop goes beyond ctrlr->batch_cache when
the batch cache is full.

> +		rpm_msg = ctrlr->batch_cache[i];
> +		ret = rpmh_rsc_write_ctrl_data(ctrlr->drv, &rpm_msg->msg);
> +		if (ret)
> +			break;
> +	}
> +	spin_unlock_irqrestore(&ctrlr->lock, flags);
> +
> +	return ret;
> +}
> +
> +static void invalidate_batch(struct rpmh_ctrlr *ctrlr)
> +{
> +	unsigned long flags;
> +	int index = 0;
> +
> +	spin_lock_irqsave(&ctrlr->lock, flags);
> +	while (ctrlr->batch_cache[index]) {

This still goes beyond ctrlr->batch_cache when the batch cache is
full.