[PATCH 5.15 256/297] sbsa_gwdt: Calculate timeout with 64-bit math

[Greg Kroah-Hartman]

5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Darren Hart <darren at os.amperecomputing.com>

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.

Fixes: abd3ac7902fb ("watchdog: sbsa: Support architecture version 1")
Reported-by: Vanshidhar Konda <vanshikonda at os.amperecomputing.com>
Signed-off-by: Darren Hart <darren at os.amperecomputing.com>
Cc: Wim Van Sebroeck <wim at linux-watchdog.org>
Cc: Guenter Roeck <linux at roeck-us.net>
Cc: linux-watchdog at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: <stable at vger.kernel.org> # 5.14.x
Reviewed-by: Guenter Roeck <linux at roeck-us.net>
Link: https://lore.kernel.org/r/7d1713c5ffab19b0f3de796d82df19e8b1f340de.1695286124.git.darren@os.amperecomputing.com
Signed-off-by: Guenter Roeck <linux at roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim at linux-watchdog.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/watchdog/sbsa_gwdt.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/watchdog/sbsa_gwdt.c
+++ b/drivers/watchdog/sbsa_gwdt.c
@@ -153,14 +153,14 @@ 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;
 }