linux-kernel - Re: [linux-pm] [RFC] usb: Add support for runtime power management of the hcd

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Message-Id: <200908131416.42189.oliver@neukum.org>
Date:	Thu, 13 Aug 2009 14:16:41 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	linux-pm@...ts.linux-foundation.org
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-usb@...r.kernel.org,
	linux-pci@...r.kernel.org, Greg KH <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] [RFC] usb: Add support for runtime power management of the hcd

Am Donnerstag, 13. August 2009 02:35:44 schrieb Matthew Garrett:

> The power savings from this are measurable but not huge - it still seems

How large?

> like a decent optimisation. The main problem is that BIOS bugs on some
> Dell laptops will kill USB if this is used, so we either default to off
> or add some quirks to handle that case (I have some ideas in that
> respect).

Your earlier failures don't look promising regarding BIOSes.
What do you have in mind?

> @@ -1968,6 +1972,9 @@ struct usb_hcd *usb_create_hcd (const struct
> hc_driver *driver, INIT_WORK(&hcd->wakeup_work, hcd_resume_work);
>  #endif
>
> +	pm_runtime_enable(dev);

So you don't get a reference from that?

> +	pm_runtime_get(dev);

What happens if you get a runtime suspend request in between? Is this a flaw
of the API?

	Regards
		Oliver

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