linux-kernel - [PATCH v13 10/11] clk: pwm: Use 64-bit division function

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Message-Id: <0efec2ac3e9d9d8d7d71e29c9ab7cdcbb02d137d.1587523702.git.gurus@codeaurora.org>
Date:   Tue, 21 Apr 2020 19:57:22 -0700
From:   Guru Das Srinagesh <gurus@...eaurora.org>
To:     linux-pwm@...r.kernel.org
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Subbaraman Narayanamurthy <subbaram@...eaurora.org>,
        David Collins <collinsd@...eaurora.org>,
        linux-kernel@...r.kernel.org,
        Guru Das Srinagesh <gurus@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org
Subject: [PATCH v13 10/11] clk: pwm: Use 64-bit division function

Since the PWM framework is switching struct pwm_args.period's datatype
to u64, prepare for this transition by using div64_u64 to handle a
64-bit divisor.

Also ensure that divide-by-zero (with fixed_rate as denominator) does
not happen with an explicit check with probe failure as a consequence.

To: David Laight <David.Laight@...LAB.COM>
To: Arnd Bergmann <arnd@...db.de>
Cc: Michael Turquette <mturquette@...libre.com>
Cc: Stephen Boyd <sboyd@...nel.org>
Cc: linux-clk@...r.kernel.org

Signed-off-by: Guru Das Srinagesh <gurus@...eaurora.org>
---
 drivers/clk/clk-pwm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
index 87fe0b0e..86f2e2d 100644
--- a/drivers/clk/clk-pwm.c
+++ b/drivers/clk/clk-pwm.c
@@ -89,7 +89,12 @@ static int clk_pwm_probe(struct platform_device *pdev)
 	}
 
 	if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
-		clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
+		clk_pwm->fixed_rate = div64_u64(NSEC_PER_SEC, pargs.period);
+
+	if (!clk_pwm->fixed_rate) {
+		dev_err(&pdev->dev, "fixed_rate cannot be zero\n");
+		return -EINVAL;
+	}
 
 	if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
 	    pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
-- 
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