From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S932320AbcITEhL (ORCPT <rfc822;w@1wt.eu>);
        Tue, 20 Sep 2016 00:37:11 -0400
Received: from bh-25.webhostbox.net ([208.91.199.152]:51932 "EHLO
        bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751029AbcITEhJ (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 20 Sep 2016 00:37:09 -0400
Subject: Re: [PATCH 3/4] watchdog: sa11x0/pxa: get rid of get_clock_tick_rate
To: Russell King - ARM Linux <linux@armlinux.org.uk>
References: <1474312335-20997-1-git-send-email-robert.jarzmik@free.fr>
 <1474312335-20997-4-git-send-email-robert.jarzmik@free.fr>
 <20160919200816.GC29242@roeck-us.net>
 <20160919223616.GN1041@n2100.armlinux.org.uk>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>,
        Daniel Mack <daniel@zonque.org>,
        Haojian Zhuang <haojian.zhuang@gmail.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>, Wim Van Sebroeck <wim@iguana.be>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-clk@vger.kernel.org, linux-watchdog@vger.kernel.org
From: Guenter Roeck <linux@roeck-us.net>
Message-ID: <0909debb-f7df-648b-95d2-23b535e5b299@roeck-us.net>
Date: Mon, 19 Sep 2016 21:37:06 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.2.0
MIME-Version: 1.0
In-Reply-To: <20160919223616.GN1041@n2100.armlinux.org.uk>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
X-Authenticated_sender: linux@roeck-us.net
X-OutGoing-Spam-Status: No, score=-1.0
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net
X-AntiAbuse: Original Domain - vger.kernel.org
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - roeck-us.net
X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net
X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net
X-Source: 
X-Source-Args: 
X-Source-Dir: 
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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@free.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.

Thanks,
Guenter