Re: [PATCH 1/3] rtc: cmos: allow using ACPI for RTC alarm instead of HPET

[Alexandre Belloni <alexandre.belloni@free-electrons.com>]

On 20/04/2018 13:59:28+0800, Zhang Rui wrote:
> Hi, Alexandre
> 
> On 四, 2018-04-19 at 16:05 +0200, Alexandre Belloni wrote:
> > Hi,
> > 
> > 
> > On 26/03/2018 21:58:01+0800, Zhang Rui wrote:
> > > 
> > > It's found that the HPET timer prevents the platform from entering
> > > Low Power S0 on some new Intel platforms.
> > > 
> > > This means that
> > > 1. users can still use RTC wake Alarm for suspend-to-idle, but the
> > > system
> > >    never enters Low Power S0, which is a waste of power.
> > > or
> > > 2. if users want to put the system into Low Power S0, they can not
> > > use
> > >    RTC as the wakeup source.
> > > 
> > > To fix this, we need to stop using the HPET timer for wake alarm.
> > > But disabling CONFIG_HPET_EMULATE_RTC is not an option because HPET
> > > emulates PIT at the same time, and this is needed on some of these
> > > platforms.
> > > 
> > > Thus, introduce a new mode (use_acpi_alarm) to the rtc_cmos driver,
> > > so that, even with CONFIG_HPET_EMULATE_RTC enabled, it's still
> > > possible to
> > > use ACPI SCI for RTC Alarm, including UIE/AIE/wkalrm, instead of
> > > HPET.
> > > 
> > > Only necessary changes are made for the new "use_acpi_alarm" mode,
> > > including
> > > 1. drop all the calls to HPET emulation code, including the HPET
> > > irq
> > >    handler for rtc interrupt.
> > > 2. enabling/disabling ACPI RTC Fixed event upon RTC UIE/AIE
> > > request.
> > > 3. acknowledge the RTC Alarm in ACPI RTC Fixed event handler.
> > > 
> > > There is no functional change made in this patch if the new mode is
> > > not
> > > enabled.
> > > 
> > > Note: this "use_acpi_alarm" mode is made based on the assumption
> > > that
> > > ACPI RTC Fixed event is reliable both at runtime and during system
> > > wakeup.
> > > And this has been verified on a couple of platforms I have,
> > > including
> > > a MS Surface Pro 4 (SKL), a Lenovo Yoga 900 (SKL), and a HP 9360
> > > (KBL).
> > > 
> > > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> > > ---
> > >  drivers/rtc/rtc-cmos.c | 111 +++++++++++++++++++++++++++++++++++
> > > --------------
> > >  1 file changed, 80 insertions(+), 31 deletions(-)
> > > 
> > I've applied the series but it didn't apply cleanly, please check
> > https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git/lo
> > g/?h=rtc-next
> > 
> Yes, I noticed this conflict as well.
> I have rebased it on top of -rc1 and it is under testing right now.
> I will rebase on your tree and resend.
> 

Rebasing on top of -rc1 is sufficient, I'm already carrying your patches
now so they are part of linux-next early in the cycle.


-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com