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

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On 10/29/23 09:10, Wim Van Sebroeck wrote:
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@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Darren Hart <darren@xxxxxxxxxxxxxxxxxxxxxx>
Cc: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: linux-watchdog@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # 5.14.x

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

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.


Thanks,
Guenter




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