linux-kernel - Re: [PATCH 1/2] rtc/ia64: remove legacy efirtc driver

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Date:   Thu, 24 Oct 2019 09:32:35 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Stephane Eranian <eranian@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] rtc/ia64: remove legacy efirtc driver

On Thu, Oct 24, 2019 at 1:20 AM Alexandre Belloni
<alexandre.belloni@...tlin.com> wrote:
>
> On 23/10/2019 21:30:29+0000, Luck, Tony wrote:
> > >> rtc-efi rtc-efi: setting system clock to 2019-10-23T18:30:23 UTC (1571855423)
> >
> > > You can remove CONFIG_RTC_HCTOSYS, this line will disappear, systemd
> > > will not like that but efirtc was not setting the system time anyway so
> > > this shouldn't change the behaviour.
> >
> >
> > Wait ... that message says "setting system clock"
> >
> > but then you say " efirtc was not setting the system time anyway".
> >
> > So did the time get set, or not?
> >
> > If it wasn't set, why does the message say that it was set?
> >
>
> What I meant was that drivers/char/efirtc.c was not setting the system
> time but when using drivers/rtc/rtc-efi.c with CONFIG_RTC_HCTOSYS, the
> kernel will use the rtc to set the system time.

arch/ia64 has a read_persistent_clock64() function, so it ends up reading
the system time regardless of the RTC driver or CONFIG_RTC_HCTOSYS.

As ia64 sets neither ARCH_HIBERNATION_POSSIBLE nor
ARCH_SUSPEND_POSSIBLE, so we could just remove the
read_persistent_clock64() and efi_gettimeofday(), relying instead
on user space (/sbin/hwclock) or CONFIG_RTC_HCTOSYS.

         Arnd