linux-kernel - Re: [PATCH] ARM: omap2: fix omap5_realtime_timer

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Message-ID: <CAK8P3a0oK-SqWHR9v0-2p3Fd_mCe2ibP_SQKf_W2A6cbEzVgWw@mail.gmail.com>
Date:   Fri, 29 May 2020 23:39:52 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Tony Lindgren <tony@...mide.com>
Cc:     SoC Team <soc@...nel.org>, Olof Johansson <olof@...om.net>,
        Stefan Agner <stefan@...er.ch>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: omap2: fix omap5_realtime_timer_init definition

On Fri, May 29, 2020 at 11:14 PM Tony Lindgren <tony@...mide.com> wrote:
> * Arnd Bergmann <arnd@...db.de> [200529 21:09]:
> >
> > #ifdef CONFIG_SOC_HAS_REALTIME_COUNTER
> > extern void omap5_realtime_timer_init(void);
> > #else
> > static inline void omap5_realtime_timer_init(void)
> > {
> > }
> > #endif
> >
> > In fact, the inline stub is what that caused the regression,
> > so I think it's ok with my patch.
>
> To me it seems not having SOC_HAS_REALTIME_COUNTER will
> cause omap5_realtime_timer_init() not get called?

Correct, this looked to me like it was the intention of that
symbol. Unfortunately there is no help text but it is user
selectable:

config SOC_HAS_REALTIME_COUNTER
        bool "Real time free running counter"
        depends on SOC_OMAP5 || SOC_DRA7XX
        default y

> That initializes clocks and calls timer_probe(). So this
> will result in non-booting system AFAIK, the header
> file stub should no rely CONFIG_SOC_HAS_REALTIME_COUNTER
> also, but rather ! CONFIG_SOC_OMAP5 || CONFIG_SOC_DRA7XX.
>
> Also the Makefile change at least seems wrong, that
> can't rely on CONFIG_SOC_HAS_REALTIME_COUNTER.

How about just removing the prompt on
CONFIG_SOC_HAS_REALTIME_COUNTER but keeping the
rest of my patch? That way it's just always enabled when
there is a chip that needs it enabled in the kernel config.

The only other usage of the symbol is

#ifdef CONFIG_SOC_HAS_REALTIME_COUNTER
void set_cntfreq(void);
#else
static inline void set_cntfreq(void)
{
}
#endif

Alternatively, we could just remove the Kconfig symbol
altogether and rely on (SOC_OMAP5 || SOC_DRA7XX)
everywhere, but that seems a little more fragile in case
there is going to be another chip that needs it.

    Arnd