linux-kernel - Re: [PATCH] sbsa_gwdt: Calculate timeout with 64-bit math

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Date:   Sun, 29 Oct 2023 17:10:56 +0100
From:   Wim Van Sebroeck <wim@...ux-watchdog.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Darren Hart <darren@...amperecomputing.com>,
        linux-kernel@...r.kernel.org,
        Vanshidhar Konda <vanshikonda@...amperecomputing.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, stable@...r.kernel.org
Subject: Re: [PATCH] sbsa_gwdt: Calculate timeout with 64-bit math

Hi Guenter,

> 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@...amperecomputing.com>
> >>>Signed-off-by: Darren Hart <darren@...amperecomputing.com>
> >>>Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>
> >>>Cc: Guenter Roeck <linux@...ck-us.net>
> >>>Cc: linux-watchdog@...r.kernel.org
> >>>Cc: linux-kernel@...r.kernel.org
> >>>Cc: linux-arm-kernel@...ts.infradead.org
> >>>Cc: <stable@...r.kernel.org> # 5.14.x
> >>
> >>Reviewed-by: Guenter Roeck <linux@...ck-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.

I can imagine what it is like. And I do know that if you wouldn't have been there, 
that I would have allready stopped being a maintainer. So I hope you can find the 
right cooping mechanisms. I also had to work non-stop the last 4 to 5 weeks and it was hell.
So I wish you all the best.

PS: picking up all patches that have your review-by tag on it as we speack.

Kind regards,
Wim.