Re: [PATCH v6 05/10] drivers: qcom: rpmh-rsc: write sleep/wake requests to TCS

[Lina Iyer]

On Wed, Apr 25 2018 at 15:41 -0600, Matthias Kaehlcke wrote:
> On Thu, Apr 19, 2018 at 04:16:30PM -0600, Lina Iyer wrote:
> > Sleep and wake requests are sent when the application processor
> > subsystem of the SoC is entering deep sleep states like in suspend.
> > These requests help lower the system power requirements when the
> > resources are not in use.
> >
> > Sleep and wake requests are written to the TCS slots but are not
> > triggered at the time of writing. The TCS are triggered by the firmware
> > after the last of the CPUs has executed its WFI. Since these requests
> > may come in different batches of requests, it is the job of this
> > controller driver to find and arrange the requests into the available
> > TCSes.
> >
> > Signed-off-by: Lina Iyer <ilina@xxxxxxxxxxxxxx>
> > Reviewed-by: Evan Green <evgreen@xxxxxxxxxxxx>
> > ---
> >  drivers/soc/qcom/rpmh-internal.h |   8 +++
> >  drivers/soc/qcom/rpmh-rsc.c      | 120 +++++++++++++++++++++++++++++++
> >  2 files changed, 128 insertions(+)
> >
> > diff --git a/drivers/soc/qcom/rpmh-internal.h b/drivers/soc/qcom/rpmh-internal.h
> > index d9a21726e568..6e19fe458c31 100644
> > --- a/drivers/soc/qcom/rpmh-internal.h
> > +++ b/drivers/soc/qcom/rpmh-internal.h
>
> <snip>
>
> > +static int find_match(const struct tcs_group *tcs, const struct tcs_cmd *cmd,
> > +		      int len)
> > +{
> > +	int i, j;
> > +
> > +	/* Check for already cached commands */
> > +	for_each_set_bit(i, tcs->slots, MAX_TCS_SLOTS) {
> > +		for (j = 0; j < len; j++) {
> > +			if (tcs->cmd_cache[i] != cmd[0].addr) {
>
> Shouldn't the condition be 'tcs->cmd_cache[i + j] != cmd[j].addr'?
Here, we are trying to find the first address from the request and its
position 'i' in the cmd_cache.

> Otherwise the code below the following if branch will never be
> executed. Either the 'tcs->cmd_cache[i] != cmd[0].addr' branch isn't
> entered because the addresses match, or the addresses don't match
> and the inner loop is aborted after the first iteration.
>
> > +				if (j == 0)
> > +					break;
> > +				WARN(tcs->cmd_cache[i + j] != cmd[j].addr,
> > +				     "Message does not match previous sequence.\n");
We now check for the sequence using the iterator 'j' only after we have
found 'i' (the beginning of our request).

I hope that helps clear the concern.

-- Lina

> > +				return -EINVAL;
> > +			} else if (j == len - 1) {
> > +				return i;
> > +			}
> > +		}
> > +	}
> > +
> > +	return -ENODATA;
> > +}