Re: [PATCH] misc: rtsx: rts5249 support runtime PM

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, 26 Nov 2020 at 15:19, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> On Thu, Nov 26, 2020 at 4:07 AM 吳昊澄 Ricky <ricky_wu@xxxxxxxxxxx> wrote:
> >
> > > -----Original Message-----
> > > From: Rafael J. Wysocki [mailto:rafael@xxxxxxxxxx]
> > > Sent: Wednesday, November 25, 2020 10:04 PM
> > > To: Bjorn Helgaas; 吳昊澄 Ricky
>
> [cut]
>
> > > > > +static void rtsx_pci_rtd3_work(struct work_struct *work)
> > > > > +{
> > > > > +     struct delayed_work *dwork = to_delayed_work(work);
> > > > > +     struct rtsx_pcr *pcr = container_of(dwork, struct rtsx_pcr,
> > > rtd3_work);
> > > > > +
> > > > > +     pcr_dbg(pcr, "--> %s\n", __func__);
> > > > > +
> > > > > +     while (pcr->pci->dev.power.usage_count.counter > 0) {
> > > > > +             if (pm_runtime_active(&(pcr->pci->dev)))
> > > > > +                     pm_runtime_put(&(pcr->pci->dev));
> > > >
> > > > I'm not a runtime PM expert, but this looks fishy.  AFAICT this is the
> > > > only driver in the tree that uses usage_count.counter this way, which
> > > > is a pretty big hint that this needs a closer look.  Cc'd Rafael.
> > >
> > > You are right, this is not correct from the PM-runtime POV.
> > >
> > > It looks like this attempts to force the PM-runtime usage counter down
> > > to 0 and it's kind of hard to say why this is done (and it shouldn't
> > > be done in the first place, because it destroys the usage counter
> > > balance).
> > >
> > > Ricky, is this an attempt to work around an issue of some sort?
> > >
> >
> > Thanks Bjorn and Rafael
> > I found when we boot up, our dev pcr->pci->dev.power.usage_count.counter always is 2,
> > Don’t know how to make it to 0 because we need to support D3 and run runtime_suspended callback function
> > Is there something wrong with us to enable runtime PM?
>
> That is possible.
>
> If you want it to be enabled by default, you need to call
> pm_runtime_allow() from the driver at probe time, in addition to
> pm_runtime_enable(), in the first place, but that only drops one
> reference, so question is where the other one comes from.

Yes, good point.

Moreover, I am wondering whether you also need to deploy support for
runtime PM for the child device (managed by
drivers/mmc/host/rtsx_pci_sdmmc.c driver), as to make the support
complete.

>
> Are the pm_runtime_get*() and pm_runtime_put*() calls balanced?

Perhaps have a look at how the drivers/misc/cardreader/rtsx_usb.c and
drivers/mmc/host/rtsx_usb_sdmmc.c have implemented this could help. I
know it's USB, but it should work quite similar in regards to runtime
PM, I think.

Kind regards
Uffe




[Index of Archives]     [Linux Memonry Technology]     [Linux USB Devel]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux