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From:   Arnd Bergmann <arnd@kernel.org>
To:     Pavel Machek <pavel@ucw.cz>, Lee Jones <lee@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Guo Ren <guoren@kernel.org>,
        Palmer Dabbelt <palmer@rivosinc.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Bill Wendling <morbo@google.com>,
        Justin Stitt <justinstitt@google.com>,
        linux-leds@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev
Subject: [PATCH] leds: sun50i-a100: avoid division-by-zero warning
Date:   Tue, 12 Dec 2023 22:45:22 +0100
Message-Id: <20231212214536.175327-1-arnd@kernel.org>
MIME-Version: 1.0
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Precedence: bulk

From: Arnd Bergmann <arnd@arndb.de>

When CONFIG_COMMON_CLK is disabled, e.g. on an x86 randconfig compile test,
clang reports a field overflow from propagating the result of a division by
zero:

drivers/leds/leds-sun50i-a100.c:309:12: error: call to '__compiletime_assert_265' declared with 'error' attribute: FIELD_PREP: value too large for the field
        control = FIELD_PREP(LEDC_T01_TIMING_CTRL_REG_T1H, timing->t1h_ns / cycle_ns) |

Avoid the problem by adding an explicit check for the zero value here. Alternatively
the assertion could be avoided with a Kconfig dependency on COMMON_CLK.

Fixes: 090a25ad9798 ("leds: sun50i-a100: New driver for the A100 LED controller")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/leds/leds-sun50i-a100.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/leds-sun50i-a100.c b/drivers/leds/leds-sun50i-a100.c
index e4a7e692a908..171cefd1ea0d 100644
--- a/drivers/leds/leds-sun50i-a100.c
+++ b/drivers/leds/leds-sun50i-a100.c
@@ -303,9 +303,13 @@ static void sun50i_a100_ledc_set_timing(struct sun50i_a100_ledc *priv)
 {
 	const struct sun50i_a100_ledc_timing *timing = &priv->timing;
 	unsigned long mod_freq = clk_get_rate(priv->mod_clk);
-	u32 cycle_ns = NSEC_PER_SEC / mod_freq;
+	u32 cycle_ns;
 	u32 control;
 
+	if (!mod_freq)
+		return;
+
+	cycle_ns = NSEC_PER_SEC / mod_freq;
 	control = FIELD_PREP(LEDC_T01_TIMING_CTRL_REG_T1H, timing->t1h_ns / cycle_ns) |
 		  FIELD_PREP(LEDC_T01_TIMING_CTRL_REG_T1L, timing->t1l_ns / cycle_ns) |
 		  FIELD_PREP(LEDC_T01_TIMING_CTRL_REG_T0H, timing->t0h_ns / cycle_ns) |
-- 
2.39.2