linux-kernel - [PATCH] pwm: tegra: Fix 32 bit build

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Date:   Thu, 10 Nov 2022 11:45:48 +0000
From:   Steven Price <steven.price@....com>
To:     Jonathan Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>
Cc:     Steven Price <steven.price@....com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, linux-kernel@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: [PATCH] pwm: tegra: Fix 32 bit build

The value of NSEC_PER_SEC << PWM_DUTY_WIDTH doesn't fix within a 32 bit
integer causing a build warning/error (and the value truncated):

  drivers/pwm/pwm-tegra.c: In function ‘tegra_pwm_config’:
  drivers/pwm/pwm-tegra.c:148:53: error: result of ‘1000000000 << 8’ requires 39 bits to represent, but ‘long int’ only has 32 bits [-Werror=shift-overflow=]
    148 |   required_clk_rate = DIV_ROUND_UP_ULL(NSEC_PER_SEC << PWM_DUTY_WIDTH,
        |                                                     ^~

Explicitly cast to a u64 to ensure the correct result.

Fixes: cfcb68817fb3 ("pwm: tegra: Improve required rate calculation")
Signed-off-by: Steven Price <steven.price@....com>
---
 drivers/pwm/pwm-tegra.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c
index 6fc4b69a3ba7..249dc0193297 100644
--- a/drivers/pwm/pwm-tegra.c
+++ b/drivers/pwm/pwm-tegra.c
@@ -145,7 +145,7 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 		 * source clock rate as required_clk_rate, PWM controller will
 		 * be able to configure the requested period.
 		 */
-		required_clk_rate = DIV_ROUND_UP_ULL(NSEC_PER_SEC << PWM_DUTY_WIDTH,
+		required_clk_rate = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC << PWM_DUTY_WIDTH,
 						     period_ns);
 
 		if (required_clk_rate > clk_round_rate(pc->clk, required_clk_rate))
-- 
2.34.1