Re: [PATCH 1/3] soc: qcom: rpmh: Update dirty flag only when data changes

[Maulik Shah]

On 2/5/2020 11:37 PM, Evan Green wrote:
> On Tue, Feb 4, 2020 at 8:14 PM Maulik Shah <mkshah@xxxxxxxxxxxxxx> wrote:
> > On 2/5/2020 6:05 AM, Evan Green wrote:
> > > On Mon, Feb 3, 2020 at 10:14 PM Maulik Shah <mkshah@xxxxxxxxxxxxxx> wrote:
> > > > Currently rpmh ctrlr dirty flag is set for all cases regardless
> > > > of data is really changed or not.
> > > >
> > > > Add changes to update it when data is updated to new values.
> > > >
> > > > Signed-off-by: Maulik Shah <mkshah@xxxxxxxxxxxxxx>
> > > > ---
> > > >    drivers/soc/qcom/rpmh.c | 15 +++++++++++----
> > > >    1 file changed, 11 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> > > > index 035091f..c3d6f00 100644
> > > > --- a/drivers/soc/qcom/rpmh.c
> > > > +++ b/drivers/soc/qcom/rpmh.c
> > > > @@ -139,20 +139,27 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
> > > >    existing:
> > > >           switch (state) {
> > > >           case RPMH_ACTIVE_ONLY_STATE:
> > > > -               if (req->sleep_val != UINT_MAX)
> > > > +               if (req->sleep_val != UINT_MAX) {
> > > >                           req->wake_val = cmd->data;
> > > > +                       ctrlr->dirty = true;
> > > > +               }
> > > Don't you need to set dirty = true for ACTIVE_ONLY state always? The
> > > conditional is just saying "if nobody set a sleep vote, then maintain
> > > this vote when we wake back up".
> > The ACTIVE_ONLY vote is cached as wake_val to be apply when wakeup happens.
> >
> > In case value didn't change,wake_val is still same as older value and
> > there is no need to mark the entire cache as dirty.
> Ah, I see it now. We don't actually cache active_only votes anywhere,
> since they're one time requests. The sleep/wake votes seem to be the
> only thing that gets cached.
>
> I was thinking it might be safer to also set dirty = true just after
> list_add_tail, since in the non-existing case this is a new batch that
> RPMh has never seen before and should always be written. But I suppose
> your checks here should cover that case, since sleep_val and wake_val
> are initialized to UINT_MAX. If you think the code might evolve, it
> might still be nice to add it.
current change seems good.
> While I'm looking at that, why do we have this needless INIT_LIST_HEAD?
>          INIT_LIST_HEAD(&req->list);
>          list_add_tail(&req->list, &ctrlr->cache);
>
> -Evan

Thanks for pointing this, i will remove this unnecessary INIT in next 
revision.

> > --
> > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation