From: Guenter Roeck <linux@roeck-us.net>
To: Darren Hart <darren@os.amperecomputing.com>
Cc: linux-kernel@vger.kernel.org,
Vanshidhar Konda <vanshikonda@os.amperecomputing.com>,
Wim Van Sebroeck <wim@linux-watchdog.org>,
linux-watchdog@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org
Subject: Re: [PATCH] sbsa_gwdt: Calculate timeout with 64-bit math
Date: Sun, 22 Oct 2023 09:58:26 -0700 [thread overview]
Message-ID: <1fae4d2c-4bc7-f169-7b84-501674a82ee4@roeck-us.net> (raw)
In-Reply-To: <ZSpbfXzFeaoUJRZ3@Fedora>
On 10/14/23 02:12, Darren Hart wrote:
> On Tue, Sep 26, 2023 at 05:45:13AM -0700, Guenter Roeck wrote:
>> On Thu, Sep 21, 2023 at 02:02:36AM -0700, Darren Hart wrote:
>>> Commit abd3ac7902fb ("watchdog: sbsa: Support architecture version 1")
>>> introduced new timer math for watchdog revision 1 with the 48 bit offset
>>> register.
>>>
>>> The gwdt->clk and timeout are u32, but the argument being calculated is
>>> u64. Without a cast, the compiler performs u32 operations, truncating
>>> intermediate steps, resulting in incorrect values.
>>>
>>> A watchdog revision 1 implementation with a gwdt->clk of 1GHz and a
>>> timeout of 600s writes 3647256576 to the one shot watchdog instead of
>>> 300000000000, resulting in the watchdog firing in 3.6s instead of 600s.
>>>
>>> Force u64 math by casting the first argument (gwdt->clk) as a u64. Make
>>> the order of operations explicit with parenthesis.
>>>
>>> Fixes: abd3ac7902fb ("watchdog: sbsa: Support architecture version 1")
>>> Reported-by: Vanshidhar Konda <vanshikonda@os.amperecomputing.com>
>>> Signed-off-by: Darren Hart <darren@os.amperecomputing.com>
>>> Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
>>> Cc: Guenter Roeck <linux@roeck-us.net>
>>> Cc: linux-watchdog@vger.kernel.org
>>> Cc: linux-kernel@vger.kernel.org
>>> Cc: linux-arm-kernel@lists.infradead.org
>>> Cc: <stable@vger.kernel.org> # 5.14.x
>>
>> Reviewed-by: Guenter Roeck <linux@roeck-us.net>
>
> Guenter or Wim, I haven't seen this land in the RCs or in next yet. Have
> you already picked it up? Anything more needed from me?
>
> Thanks,
>
Sorry, I am suffering from what I can only describe as a severe case of
maintainer/reviewer PTSD, and I have yet to find a way of dealing with that.
Guenter
next prev parent reply other threads:[~2023-10-22 16:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-21 9:02 [PATCH] sbsa_gwdt: Calculate timeout with 64-bit math Darren Hart
2023-09-26 12:45 ` Guenter Roeck
2023-10-14 9:12 ` Darren Hart
2023-10-22 16:58 ` Guenter Roeck [this message]
2023-10-26 17:17 ` Darren Hart
2023-10-29 15:53 ` Wim Van Sebroeck
2023-10-29 16:10 ` Wim Van Sebroeck
2023-10-29 17:00 ` Guenter Roeck
2023-10-30 16:21 ` Darren Hart
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