From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thierry Reding <thierry.reding@gmail.com>
Subject: Re: [PATCH v2] pwm: samsung: fix to use lowest div for large enough
 modulation bits
Date: Mon, 5 Sep 2016 08:53:08 +0200
Message-ID: <20160905065308.GF3532@ulmo.ba.sec>
References: <1470133006-4272-1-git-send-email-sw0312.kim@samsung.com>
 <20160816142201.12672-1-sw0312.kim@samsung.com>
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In-Reply-To: <20160816142201.12672-1-sw0312.kim@samsung.com>
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To: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, k.kozlowski@samsung.com, linux-pwm@vger.kernel.org, tomasz.figa@gmail.com, jy0922.shim@samsung.com, krzk@kernel.org
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On Tue, Aug 16, 2016 at 11:22:01PM +0900, Seung-Woo Kim wrote:
> 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 s3c24xx, so this patch fixes
> to use lowest div for the case. This patch removes following UBSAN
> warning:
>=20
>    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>] (p=
wm_samsung_config+0x508/0x6a4)
>    [<c0694b28>] (pwm_samsung_config) from [<c069286c>] (pwm_apply_state+0=
x174/0x40c)
>    [<c069286c>] (pwm_apply_state) from [<c0b2e070>] (pwm_fan_probe+0xc8/0=
x488)
>    [<c0b2e070>] (pwm_fan_probe) from [<c07ba8b0>] (platform_drv_probe+0x7=
0/0x150)
>    [...]
>=20
> Cc: Tomasz Figa <tomasz.figa@gmail.com>
> Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> ---
> Changes from v1
>  * Remove too complex condition, instead, just checking simple variant->b=
its as Krzysztof's suggestion
>  * Add comment from Tomasz
>=20
> The UBSAN warning from ARM is reported with the patch in following link:
> https://patchwork.kernel.org/patch/9189575/
> ---
>  drivers/pwm/pwm-samsung.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)

Applied, thanks.

Thierry

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