[PATCH] USB: host: ehci_atmel: Add suspend/resume support

[boris.brezillon@free-electrons.com (Boris Brezillon)]

Hi Sylvain,

On Sat, 17 Jan 2015 02:34:42 +0100
Alexandre Belloni <alexandre.belloni@free-electrons.com> wrote:

> Hi,
> 
> You should probably put the susbsytem maintainers in copy too. As
> reported by get_maintainer.pl:
> Alan Stern <stern@rowland.harvard.edu> (maintainer:USB EHCI DRIVER)
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> (supporter:USB SUBSYSTEM)
> 
> They will be the one taking the patch.
> 
> And when dealing with PM on AT91, please copy
> Wenyou Yang <wenyou.yang@atmel.com>
> 
> 
> On 16/01/2015 at 20:41:14 +0100, Sylvain Rochet wrote :
> > This patch add suspend/resume support for Atmel EHCI, mostly
> > about disabling and unpreparing clocks so USB PLL is stopped
> > before entering sleep state.
> > 
> > Signed-off-by: Sylvain Rochet <sylvain.rochet@finsecur.com>
> 
> Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> 
> > +
> > +	if (at91_suspend_entering_slow_clock())
> > +		atmel_stop_clock();
> > +
> 
> We should definitely find a way to get rid of
> at91_suspend_entering_slow_clock() at some point in time.
> 
> 

Can't we just disable clocks without testing for target_state ==
PM_SUSPEND_MEM (which is exactly what at91_suspend_entering_slow_clock
does [1]) when entering suspend ?
I mean, IMHO other kind of suspend should still benefit from the power
save induced by this PLL deactivation.

Is there such a big penalty when resuming the device if the PLL and
peripheral clocks are disabled ?

[1]http://lxr.free-electrons.com/source/arch/arm/mach-at91/pm.c#L116


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com