From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>,
Andi Shyti <andi.shyti@kernel.org>,
stable@vger.kernel.org
Subject: [PATCH v1 1/1] i2c: mpc: Fix timeout calculations
Date: Thu, 18 Jun 2026 16:49:34 +0200 [thread overview]
Message-ID: <20260618144934.3249950-1-andriy.shevchenko@linux.intel.com> (raw)
ON the 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 not 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")
Cc: stable@vger.kernel.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
drivers/i2c/busses/i2c-mpc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 28c5c5c1fb7a..a21fa45bd64c 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 {
--
2.50.1
reply other threads:[~2026-06-18 14:49 UTC|newest]
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