linux-kernel - Re: [PATCH 3/4] watchdog: sa11x0/pxa: get rid of get_clock_tick

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Message-ID: <87h99bdrhh.fsf@belgarion.home>
Date:   Tue, 20 Sep 2016 08:18:02 +0200
From:   Robert Jarzmik <robert.jarzmik@...e.fr>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Daniel Mack <daniel@...que.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wim Van Sebroeck <wim@...ana.be>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-watchdog@...r.kernel.org
Subject: Re: [PATCH 3/4] watchdog: sa11x0/pxa: get rid of get_clock_tick_rate

Guenter Roeck <linux@...ck-us.net> writes:

> On 09/19/2016 03:36 PM, Russell King - ARM Linux wrote:
>> On Mon, Sep 19, 2016 at 01:08:16PM -0700, Guenter Roeck wrote:
>>> On Mon, Sep 19, 2016 at 09:12:14PM +0200, Robert Jarzmik wrote:
>>>> The OS timer rate used for the watchdog can now be fetched from the
>>>> standard clock API. This will remove the last user of
>>>> get_clock_tick_rate() in both pxa and sa11x0 architectures.
>>>>
>>>> Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>
>>>
>>> Did you test this ? Potential problem, if built into the kernel, could be that
>>> the clocks might not be ready by the time the driver is instantiated. Unless
>>> this is converted to a platform driver, it won't be able to handle a
>>> -EPROBE_DEFER from the clock subsystem.
>>
>> Really not a problem at all.  The OSTIMER0 is required for the system
>> tick, and if that's not present, the kernel will be without any kind
>> of time keeping, so a missing watchdog driver is the least of the
>> problems.
>>
>> Therefore, both PXA and SA11x0 register their clocks really early to
>> ensure that OSTIMER0 is available by the time_init() stage, which is
>> way before driver probe time.
>>
>
> You are right. And, at least in qemu, it actually works.
Hi Guenter,

Yes, it was tested on pxa25x (lubbock) and pxa27x (mainstone).

Cheers.

-- 
Robert