linux-kernel - [PATCH 5.15 457/779] clk: qcom: clk-rcg2: Make sure to not write d=0 to the NMD register

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Message-Id: <20220815180356.812632127@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 20:01:41 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nikita Travkin <nikita@...n.ru>,
        Stephen Boyd <sboyd@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 457/779] clk: qcom: clk-rcg2: Make sure to not write d=0 to the NMD register

From: Nikita Travkin <nikita@...n.ru>

[ Upstream commit d0696770cef35a1fd16ea2167e2198c18aa6fbfe ]

Sometimes calculation of d value may result in 0 because of the
rounding after integer division. This causes the following error:

[  113.969689] camss_gp1_clk_src: rcg didn't update its configuration.
[  113.969754] WARNING: CPU: 3 PID: 35 at drivers/clk/qcom/clk-rcg2.c:122 update_config+0xc8/0xdc

Make sure that D value is never zero.

Fixes: 7f891faf596e ("clk: qcom: clk-rcg2: Add support for duty-cycle for RCG")
Signed-off-by: Nikita Travkin <nikita@...n.ru>
Reviewed-by: Stephen Boyd <sboyd@...nel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Link: https://lore.kernel.org/r/20220612145955.385787-3-nikita@trvn.ru
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/clk/qcom/clk-rcg2.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
index ebdbc842b98a..c3823cc32edc 100644
--- a/drivers/clk/qcom/clk-rcg2.c
+++ b/drivers/clk/qcom/clk-rcg2.c
@@ -13,6 +13,7 @@
 #include <linux/rational.h>
 #include <linux/regmap.h>
 #include <linux/math64.h>
+#include <linux/minmax.h>
 #include <linux/slab.h>
 
 #include <asm/div64.h>
@@ -429,9 +430,11 @@ static int clk_rcg2_set_duty_cycle(struct clk_hw *hw, struct clk_duty *duty)
 	/* Calculate 2d value */
 	d = DIV_ROUND_CLOSEST(n * duty_per * 2, 100);
 
-	 /* Check bit widths of 2d. If D is too big reduce duty cycle. */
-	if (d > mask)
-		d = mask;
+	/*
+	 * Check bit widths of 2d. If D is too big reduce duty cycle.
+	 * Also make sure it is never zero.
+	 */
+	d = clamp_val(d, 1, mask);
 
 	if ((d / 2) > (n - m))
 		d = (n - m) * 2;
-- 
2.35.1