Commit 04d68dea authored Aug 16, 2016 by Seung-Woo Kim Committed by Thierry Reding Sep 06, 2016

pwm: samsung: Fix to use lowest div for large enough modulation bits



From pwm_samsung_calc_tin(), there is routine to find the lowest divider
possible to generate lower frequency than requested one. But it is
always possible to generate requested frequency with large enough
modulation bits except on s3c24xx, so this patch fixes to use lowest div
for the case. This patch removes following UBSAN warning:

   UBSAN: Undefined behaviour in drivers/pwm/pwm-samsung.c:197:13
   shift exponent 32 is too large for 32-bit type 'long unsigned int'
   [...]
   [<c0670248>] (ubsan_epilogue) from [<c06707b4>] (__ubsan_handle_shift_out_of_bounds+0xd8/0x120)
   [<c06707b4>] (__ubsan_handle_shift_out_of_bounds) from [<c0694b28>] (pwm_samsung_config+0x508/0x6a4)
   [<c0694b28>] (pwm_samsung_config) from [<c069286c>] (pwm_apply_state+0x174/0x40c)
   [<c069286c>] (pwm_apply_state) from [<c0b2e070>] (pwm_fan_probe+0xc8/0x488)
   [<c0b2e070>] (pwm_fan_probe) from [<c07ba8b0>] (platform_drv_probe+0x70/0x150)
   [...]

Cc: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

parent 549c50af

drivers/pwm/pwm-samsung.c

+12 −3

Original line number	Diff line number	Diff line
		@@ -193,9 +193,18 @@ static unsigned long pwm_samsung_calc_tin(struct samsung_pwm_chip *chip,
		* divider settings and choose the lowest divisor that can generate
		* frequencies lower than requested.
		*/
		if (variant->bits < 32) {
		/* Only for s3c24xx */
		for (div = variant->div_base; div < 4; ++div)
		if ((rate >> (variant->bits + div)) < freq)
		break;
		} else {
		/*
		* Other variants have enough counter bits to generate any
		* requested rate, so no need to check higher divisors.
		*/
		div = variant->div_base;
		}

		pwm_samsung_set_divisor(chip, chan, BIT(div));

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