> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Kevin Hilman
> Sent: Saturday, July 09, 2011 2:24 AM
> To: Balaji T K
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected]; [email protected];
> [email protected]
> Subject: Re: [PATCHv4 2/3] MMC: OMAP: HSMMC: add runtime pm support
>
> Balaji T K <[email protected]> writes:
>
> > add runtime pm support to HSMMC host controller
> > Use runtime pm API to enable/disable HSMMC clock
> > Use runtime autosuspend APIs to enable auto suspend delay
> >
> > Based on OMAP HSMMC runtime implementation by Kevin Hilman, Kishore
> Kadiyala
> >
> > Signed-off-by: Balaji T K <[email protected]>
>
> It's not relevant for this merge window, but I'm exploring some future
> changes to our PM core code and have a question about how MMC works for
> system suspend.
>
> Basially, the question is: can the driver be reworked such that a system
> suspend does not need to runtime resume the device? For most devices,
> we kind of expect that if the device is runtime suspended, a system
> suspend will have nothing extra to do, but this driver runtime resumes
> the device during system suspend in order to do "stuff", which I
> admitedly don't fully undestand.
>
> Ideally, the "stuff" needed for runtime suspend and system suspend could
> be made to be common such that a system suspend of a runtime suspended
> device would be a noop.
>
> Is this possible?
>
> Kevin
During system suspended patch, a callback named .prepare will be first done
before .suspend is called, and .complete callback will be called after .resume
is called. These two callbacks are in pair. If driver can implement the
.prepare and hold the usage count in this callback, then runtime pm
suspend/resume will not happen during device suspending. So there will be no
need to add pm_runtime_get* and pm_runtime_put* in .suspend/.resume.
BTW, if .prepare has hold the usage count, then .complete callback need to
release the usage count and put device in runtime suspended mode.
Thanks
Chuanxiao
>
> > @@ -2100,6 +2087,7 @@ static int omap_hsmmc_suspend(struct device *dev)
> > return 0;
> >
> > if (host) {
> > + pm_runtime_get_sync(host->dev);
> > host->suspended = 1;
> > if (host->pdata->suspend) {
> > ret = host->pdata->suspend(&pdev->dev,
> > @@ -2114,13 +2102,11 @@ static int omap_hsmmc_suspend(struct device
> *dev)
> > }
> > cancel_work_sync(&host->mmc_carddetect_work);
> > ret = mmc_suspend_host(host->mmc);
> > - mmc_host_enable(host->mmc);
> > +
> > if (ret == 0) {
> > omap_hsmmc_disable_irq(host);
> > OMAP_HSMMC_WRITE(host->base, HCTL,
> > OMAP_HSMMC_READ(host->base, HCTL) & ~SDBP);
> > - mmc_host_disable(host->mmc);
> > - clk_disable(host->iclk);
> > if (host->got_dbclk)
> > clk_disable(host->dbclk);
> > } else {
> > @@ -2132,9 +2118,8 @@ static int omap_hsmmc_suspend(struct device *dev)
> > dev_dbg(mmc_dev(host->mmc),
> > "Unmask interrupt failed\n");
> > }
> > - mmc_host_disable(host->mmc);
> > }
> > -
> > + pm_runtime_put_sync(host->dev);
> > }
> > return ret;
> > }
> --
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