linux-kernel - [PATCH v2] clk: si5341: Adjust rate rounding in si5341_output_clk_determine

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Message-ID: <20240919122905.14026-1-amishin@t-argos.ru>
Date: Thu, 19 Sep 2024 15:29:05 +0300
From: Aleksandr Mishin <amishin@...rgos.ru>
To: Maxime Ripard <mripard@...nel.org>
CC: Aleksandr Mishin <amishin@...rgos.ru>, Michael Turquette
	<mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>,
	<linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<lvc-project@...uxtesting.org>
Subject: [PATCH v2] clk: si5341: Adjust rate rounding in si5341_output_clk_determine_rate()

In si5341_output_clk_determine_rate() division by zero is possible if the
following conditions are met:
- rate > (parent_rate / 2);
- (parent_rate / 2) is not multiple of rate;
- CLK_SET_RATE_PARENT flag is not set.

Add zero value check and provide a higher rate in such case.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 3044a860fd09 ("clk: Add Si5341/Si5340 driver")
Suggested-by: Stephen Boyd <sboyd@...nel.org>
Signed-off-by: Aleksandr Mishin <amishin@...rgos.ru>
---
v1->v2: Update "Fixes" tag, in case of possible division by zero provide
 a higher rate as suggested by Stephen

 drivers/clk/clk-si5341.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/clk-si5341.c b/drivers/clk/clk-si5341.c
index 6e8dd7387cfd..278fb341d3d7 100644
--- a/drivers/clk/clk-si5341.c
+++ b/drivers/clk/clk-si5341.c
@@ -855,7 +855,7 @@ static int si5341_output_clk_determine_rate(struct clk_hw *hw,
 	} else {
 		/* We cannot change our parent's rate, report what we can do */
 		r /= rate;
-		rate = req->best_parent_rate / (r << 1);
+		rate = r ? req->best_parent_rate / (r << 1) : req->best_parent_rate;
 	}
 
 	req->rate = rate;
-- 
2.30.2