Re: [PATCH] mmc: core: add auto bkops support

[Shawn Lin]

å 2016/6/22 22:08, Alex Lemberg åé:
> HI Shawn,
>
> On 6/21/16, 4:44 AM, "Shawn Lin" <shawn.lin@xxxxxxxxxxxxxx> wrote:
>
> > On 2016/6/20 21:33, Alex Lemberg wrote:
> > > Hi Shawn,
> > >
> > > [â]
> > >
> > > > > > +
> > > > > > +static int mmc_stop_auto_bkops(struct mmc_card *card)
> > > > > > +{
> > > > > > +	int err = 0;
> > > > > > +
> > > > > > +	if (!card->ext_csd.auto_bkops_en)
> > > > > > +		return 0;
> > > > > > +
> > > > >
> > > > > Shouldnât the BKOPS_STATUS be checked prior to disabling the BKOPS activity of the device?
> > > >
> > > > Hrmm.. I read the whole section of spec for it, and I did find this
> > > > requirement for manul bkops but not for the auto one. So what should we
> > > > do if using the auto one?
> > >
> > > In case of AUTO BKOPS, the eMMC Device should perform internal GC
> > > in the same way as in case of MANUAL BKOPS.
> > > The only difference is a host awareness.
> >
> > agree.
> >
> > > Although there is no requirement in the spec, I think the driver can
> > > give some time to the device to perform/complete its internal GC during the idle time.
> > > Thus I think we can check the BKOPS_STATUS on Runtime suspend.
> >
> > We shouldn't diable bkops on *runtime* suspend as it's just the right
> > time for firmware to do GC. We could consider to check and wait for
> > the status when doing poweroff, although it seems firmware should be
> > able to accept the disable cmd and deal the on-going work perfectly
> > when doing bkops without host's awareness, just the same way as suddent
> > power loss cases.
>
> If I am not wrong, in current implementation of runtime suspend,
> the driver stops BKOPS (send HPI) just before sending sleep command,
> see _mmc_suspend(), depends on âMMC_CAP_AGGRESSIVE_PMâ flag.
> In this case, the eMMC device will not have enough time to perform internal
> BKOPS in both â Manual and Auto BKOPS configurations.

ye, so it seems a pre-exiting issue before introducing auto bkops?
I think we can push another patch to improve it but not handling
it for this $SUBJECT, does it sound ok to you?

> For the poweroff, it should be OK with a current implementation of
> PON (mmc_poweroff_notify())
>
> > Also I don't know whether the firmware will reflect its status on
> > BKOPS_STATUS or not when enabling the auto one. I will do more test.
> >
> > Anyway, thanks for sharing your thought.
> > Also Adrian point out that currently we trigger manual bkosp from
> > userspace via mmc-utils, and I agreed we shouldn't force kernel stack
> > to enable it defaultly. So I'm prone not to update this $SUBJECT and
> > migrate it to mmc-utils later.
> >
> > > [â]
> > >
> > > Thanks,
> > > Alex
> >
> >
> > --
> > Best Regards
> > Shawn Lin


--
Best Regards
Shawn Lin