MUSB peripheral DMA regression caused by driver core runtime PM change

[balbi@ti.com (Felipe Balbi)]

Hi,

Tony Lindgren <tony@atomide.com> writes:
> From: Tony Lindgren <tony@atomide.com>
> 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 <grygorii.strashko@ti.com>.
>
> 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 <grygorii.strashko@ti.com>
> Signed-off-by: Tony Lindgren <tony@atomide.com>

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 <balbi@ti.com>

> --- 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
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