[PATCH 07/12] pm: at91: the standby mode uses the same sram function as the suspend to memory mode
Yang, Wenyou
Wenyou.Yang at atmel.com
Sun Jan 25 19:06:31 PST 2015
Hi Sylvain,
Thank you for review.
> -----Original Message-----
> From: Sylvain Rochet [mailto:sylvain.rochet at finsecur.com]
> Sent: Saturday, January 24, 2015 1:33 AM
> To: Yang, Wenyou
> Cc: Ferre, Nicolas; linux at arm.linux.org.uk; linux-kernel at vger.kernel.org;
> alexandre.belloni at free-electrons.com; peda at axentia.se; linux-arm-
> kernel at lists.infradead.org
> Subject: Re: [PATCH 07/12] pm: at91: the standby mode uses the same sram
> function as the suspend to memory mode
>
> Hello Wenyou,
>
> On Tue, Jan 20, 2015 at 04:17:00PM +0800, Wenyou Yang wrote:
> >
> > diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c index
> > 691e6db..a1010f0 100644
> > --- a/arch/arm/mach-at91/pm.c
> > +++ b/arch/arm/mach-at91/pm.c
> (...)
> > static int at91_pm_enter(suspend_state_t state) {
> > at91_pinctrl_gpio_suspend();
> >
> > switch (state) {
> > + /*
> > + * Suspend-to-RAM is like STANDBY plus slow clock mode, so
> > + * drivers must suspend more deeply, the master clock switches
> > + * to the clk32k and turns off the main oscillator
> > + *
> > + * STANDBY mode has *all* drivers suspended; ignores irqs not
> > + * marked as 'wakeup' event sources; and reduces DRAM power.
> > + * But otherwise it's identical to PM_SUSPEND_ON: cpu idle, and
> > + * nothing fancy done with main or cpu clocks.
> > + */
> > + case PM_SUSPEND_MEM:
> > + case PM_SUSPEND_STANDBY:
> (...)
> > - case PM_SUSPEND_MEM:
> > - /*
> > - * Ensure that clocks are in a valid state.
> > - */
> > - if (!at91_pm_verify_clocks())
> > - goto error;
> (...)
> > + if (!at91_pm_verify_clocks())
> > + goto error;
> >
> (...)
> > - case PM_SUSPEND_STANDBY:
> > - /*
> > - * NOTE: the Wait-for-Interrupt instruction needs to be
>
> By doing that at91_pm_verify_clocks() is now called for both MEM and STANDBY
> targets.
>
> In my opinion this function is misnamed and should be called
> at91_pm_verify_clocks_for_slow_clock_mode(). This function actually checks if
> we can safely switch to slow clock mode, if some peripherals are still using the
> master clock, we abort the suspend because we can't suspend in good condition.
> Hard unclocking peripherals which ask for a soft stop, like USB controllers, is
> something we should avoid doing.
>
> This function checks if USB PLL and PLL B are stopped, if PCK0..PCK3 are
> stopped too (or just using the 32k clock). If all drivers suspended correctly this is
> the state we expect and we can suspend in a deep state.
>
> Not this is currently not the case in linux-next, suspend/resume support to all Atmel
> USB drivers (ehci-atmel,ohci-at91,atmel_usba,at91_udc) are in my series:
> [PATCHv7 0/6] USB: host: Atmel OHCI and EHCI drivers improvements
> <1421761144-11767-1-git-send-email-sylvain.rochet at finsecur.com>
> [PATCHv6 0/5] USB: gadget: atmel_usba_udc: Driver improvements
> <1421945805-31129-1-git-send-email-sylvain.rochet at finsecur.com>
>
> We are not going to change any clock for STANDBY target, there is no clock to
> check, so we don't need to call at91_pm_verify_clocks() for this target.
I will change in the next version.
Thanks.
>
> Sylvain
Best Regards,
Wenyou Yang
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