linux-kernel - Re: [PATCH v2 06/10] usb: xhci: Enable runtime pm in xhci-plat

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Message-ID: <Pine.LNX.4.44L0.1303021050210.11936-100000@netrider.rowland.org>
Date:	Sat, 2 Mar 2013 10:53:16 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Vivek Gautam <gautam.vivek@...sung.com>
cc:	linux-usb@...r.kernel.org, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-samsung-soc@...r.kernel.org>,
	<gregkh@...uxfoundation.org>, <balbi@...com>,
	<sarah.a.sharp@...ux.intel.com>, <kgene.kim@...sung.com>,
	<kishon@...com>, Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v2 06/10] usb: xhci: Enable runtime pm in xhci-plat

On Sat, 2 Mar 2013, Vivek Gautam wrote:

> By enabling runtime pm in this driver allows users of
> xhci-plat to enter into runtime pm. This is not full
> runtime pm support (AKA xhci-plat doesn't actually power
> anything off when in runtime suspend mode) but,
> just basic enablement.
> 
> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
> CC: Doug Anderson <dianders@...omium.org>
> ---
>  drivers/usb/host/xhci-plat.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index c9c7e13..595cb52 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -12,6 +12,7 @@
>   */
>  
>  #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
>  
> @@ -149,6 +150,8 @@ static int xhci_plat_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto put_usb3_hcd;
>  
> +	pm_runtime_enable(&pdev->dev);

This is generally not a good idea.  You shouldn't enable a device for 
runtime PM without first telling the PM core what state it is in.

> @@ -174,6 +177,10 @@ static int xhci_plat_remove(struct platform_device *dev)
>  	struct usb_hcd	*hcd = platform_get_drvdata(dev);
>  	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
>  
> +	if (!pm_runtime_suspended(&dev->dev))
> +		pm_runtime_put(&dev->dev);
> +	pm_runtime_disable(&dev->dev);
> +
>  	usb_remove_hcd(xhci->shared_hcd);
>  	usb_put_hcd(xhci->shared_hcd);

This is very strange.  Why have a pm_runtime_put with no balancing 
pm_runtime_get?

And why use an async routine when you're about to unbind the driver?  
Don't you want the callback to occur before the unbinding?

Alan Stern

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