From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: Thu, 18 Jun 2026 14:49:34 +0000 (+0200)
Subject: i2c: mpc: Fix timeout calculations
X-Git-Tag: v7.2-rc1~6^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2e9a7f68329be41792c0b123c28e6c53c2fa2249;p=thirdparty%2Fkernel%2Flinux.git

i2c: mpc: Fix timeout calculations

At first glance the harmless cleanup of the driver does nothing bad.
However, as the operator precedence list states the '*' (multiplication)
and '/' division operators have order 5 with left-to-right associativity
the *= has order 17 and associativity right-to-left. It wouldn't be
a problem to replace

	foo = foo * HZ / 1000000;

with

	foo *= HZ / 1000000;

if HZ constant is in Hertz. The problem is that in the Linux kernel HZ is
defined in jiffy units, which is order of magnitude smaller than a million.
That's why operator precedence has a crucial role here. Fix the regression
by reverting pre-optimized calculations.

Fixes: be40a3ae719f ("i2c: mpc: Use of_property_read_u32 instead of of_get_property")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: <stable@vger.kernel.org> # v6.4+
Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260618144934.3249950-1-andriy.shevchenko@linux.intel.com
---

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 28c5c5c1fb7a6..a21fa45bd64c4 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -844,7 +844,7 @@ static int fsl_i2c_probe(struct platform_device *op)
 					      "fsl,timeout", &mpc_ops.timeout);
 
 	if (!result) {
-		mpc_ops.timeout *= HZ / 1000000;
+		mpc_ops.timeout = mpc_ops.timeout * HZ / 1000000;
 		if (mpc_ops.timeout < 5)
 			mpc_ops.timeout = 5;
 	} else {