Patch "sbsa_gwdt: Calculate timeout with 64-bit math" has been added to the 6.6-stable tree

This is a note to let you know that I've just added the patch titled

sbsa_gwdt: Calculate timeout with 64-bit math

to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
sbsa_gwdt-calculate-timeout-with-64-bit-math.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From 5d6aa89bba5bd6af2580f872b57f438dab883738 Mon Sep 17 00:00:00 2001
From: Darren Hart <[email protected]>
Date: Thu, 21 Sep 2023 02:02:36 -0700
Subject: sbsa_gwdt: Calculate timeout with 64-bit math

From: Darren Hart <[email protected]>

commit 5d6aa89bba5bd6af2580f872b57f438dab883738 upstream.

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.

---
 drivers/watchdog/sbsa_gwdt.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -152,14 +152,14 @@ static int sbsa_gwdt_set_timeout(struct
 	timeout = clamp_t(unsigned int, timeout, 1, wdd->max_hw_heartbeat_ms / 1000);
 
 	if (action)
-		sbsa_gwdt_reg_write(gwdt->clk * timeout, gwdt);
+		sbsa_gwdt_reg_write((u64)gwdt->clk * timeout, gwdt);
 	else
 		/*
 		 * In the single stage mode, The first signal (WS0) is ignored,
 		 * the timeout is (WOR * 2), so the WOR should be configured
 		 * to half value of timeout.
 		 */
-		sbsa_gwdt_reg_write(gwdt->clk / 2 * timeout, gwdt);
+		sbsa_gwdt_reg_write(((u64)gwdt->clk / 2) * timeout, gwdt);
 
 	return 0;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-6.6/sbsa_gwdt-calculate-timeout-with-64-bit-math.patch

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