Subject: MUSB peripheral DMA regression caused by driver core runtime PM change

From: [email-masked] (Tony Lindgren)
Date: Wed, 28 Oct 2015 10:14:41 -0700

* Felipe Balbi <[email-masked]> [151023 09:48]:
> 
> Hi,
> 
> Tony Lindgren <[email-masked]> writes:
> > From: Tony Lindgren <[email-masked]>
> > Date: Fri, 23 Oct 2015 09:03:22 -0700
> > Subject: [PATCH] usb: musb: omap2430: Fix regression caused by driver core
> >  change
> >
> > Commit ddef08dd00f5 ("Driver core: wakeup the parent device before trying
> > probe") started automatically ensuring the parent device is enabled when
> > the child gets probed.
> >
> > This however caused a regression for MUSB omap2430 interface as the
> > runtime PM for the parent device needs the child initialized to access
> > the MUSB hardware registers.
> >
> > Let's delay the enabling of PM runtime for the parent until the child
> > has been properly initialized as suggested in an earlier patch by
> > Grygorii Strashko <[email-masked]>.
> >
> > In addition to delaying pm_runtime_enable, we now also need to make sure
> > the parent is enabled during omap2430_musb_init. We also want to propagate
> > an error from omap2430_runtime_resume if struct musb is not initialized.
> >
> > Note that we use pm_runtime_put_noidle here for both the child and parent
> > to prevent an extra runtime_suspend/resume cycle.
> >
> > Let's also add some comments to avoid confusion between the
> > two different devices.
> >
> > Fixes: ddef08dd00f5 ("Driver core: wakeup the parent device before
> > trying probe")
> > Suggested-by: Grygorii Strashko <[email-masked]>
> > Signed-off-by: Tony Lindgren <[email-masked]>
> 
> I'm fine with this patch to fix this v4.3 regression. Greg, do you want
> a pull request or can you take this in as a patch ? In any case:
> 
> Acked-by: Felipe Balbi <[email-masked]>

OK no response for a few days, so I'll pick this up into omap-for-v4.3/fixes
as I have another fix there too.

Regards,

Tony

> > --- a/drivers/usb/musb/omap2430.c
> > +++ b/drivers/usb/musb/omap2430.c
> > @@ -391,9 +391,20 @@ static int omap2430_musb_init(struct musb *musb)
> >  	}
> >  	musb->isr = omap2430_musb_interrupt;
> >  
> > +	/*
> > +	 * Enable runtime PM for musb parent (this driver). We can't
> > +	 * do it earlier as struct musb is not yet allocated and we
> > +	 * need to touch the musb registers for runtime PM.
> > +	 */
> > +	pm_runtime_enable(glue->dev);
> > +	status = pm_runtime_get_sync(glue->dev);
> > +	if (status < 0)
> > +		goto err1;
> > +
> >  	status = pm_runtime_get_sync(dev);
> >  	if (status < 0) {
> >  		dev_err(dev, "pm_runtime_get_sync FAILED %d\n", status);
> > +		pm_runtime_put_sync(glue->dev);
> >  		goto err1;
> >  	}
> >  
> > @@ -426,6 +437,7 @@ static int omap2430_musb_init(struct musb *musb)
> >  	phy_power_on(musb->phy);
> >  
> >  	pm_runtime_put_noidle(musb->controller);
> > +	pm_runtime_put_noidle(glue->dev);
> >  	return 0;
> >  
> >  err1:
> > @@ -626,7 +638,11 @@ static int omap2430_probe(struct platform_device *pdev)
> >  		goto err2;
> >  	}
> >  
> > -	pm_runtime_enable(&pdev->dev);
> > +	/*
> > +	 * Note that we cannot enable PM runtime yet for this
> > +	 * driver as we need struct musb initialized first.
> > +	 * See omap2430_musb_init above.
> > +	 */
> >  
> >  	ret = platform_device_add(musb);
> >  	if (ret) {
> > @@ -675,11 +691,12 @@ static int omap2430_runtime_resume(struct device *dev)
> >  	struct omap2430_glue		*glue = dev_get_drvdata(dev);
> >  	struct musb			*musb = glue_to_musb(glue);
> >  
> > -	if (musb) {
> > -		omap2430_low_level_init(musb);
> > -		musb_writel(musb->mregs, OTG_INTERFSEL,
> > -				musb->context.otg_interfsel);
> > -	}
> > +	if (!musb)
> > +		return -EPROBE_DEFER;
> > +
> > +	omap2430_low_level_init(musb);
> > +	musb_writel(musb->mregs, OTG_INTERFSEL,
> > +		    musb->context.otg_interfsel);
> >  
> >  	return 0;
> >  }
> 
> -- 
> balbi