Messages in this thread | | | Date | Wed, 29 Jul 2015 11:08:30 +0200 | Subject | Re: [rtc-linux] [PATCH] drivers/rtc/rtc-pl031.c: reset registers in init flow | From | Linus Walleij <> |
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On Wed, Jul 29, 2015 at 8:02 AM, Leo Yan <leo.yan@linaro.org> wrote:
> When use rtc-pl031 for suspend test on Hisilicon's SoC Hi6220, Usually > the data register (DR) will read back as value zero. So the suspend > test code will set the match register (MR) for 10 seconds' timeout; But > there have chance later will read back some random values from DR > register; So finally miss with match value and will not trigger > waken up event anymore. > > This issue can be dismissed by reset registers in initialization flow; > And this code have no harm for ST's variant. > > Signed-off-by: Leo Yan <leo.yan@linaro.org>
I don't understand this...
> + /* Init registers */ > + writel(0x0, ldata->base + RTC_LR);
This will reset the clock to jan 1st 1970 on every reboot. The idea is that the RTC should *preserve* the system time if you reboot the system, so NACK.
Usually userspace has a script using hwclock to read the system time from the rtc to system time with hwclock -s after userspace comes up. Likewise it writes it back with hwclock -w before rebooting.
> + writel(0x0, ldata->base + RTC_DR);
This is a read-only register in the PL031 clean variant. What do you want to achieve here? Is this register writeable on the HiSilicon?
> + writel(0x0, ldata->base + RTC_IMSC);
OK
> + writel(RTC_BIT_AI, ldata->base + RTC_ICR);
So why do we want to have the alarm enabled by default, before the kernel nor userspace has requested it?
If your problem is with suspend/resume I suggest you work on the [runtime]_suspend/resume hooks instead of probe(). Possibly you need to save/restore state across suspend/resume.
Yours, Linus Walleij
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