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@xxxxxxxxx> > --- > 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/log/?h=rtc-next -- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
