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Date: Wed, 24 Apr 2024 16:19:04 +0200
From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To: George Stark <gnstark@salutedevices.com>
Cc: neil.armstrong@linaro.org, khilman@baylibre.com, jbrunet@baylibre.com, 
	martin.blumenstingl@googlemail.com, thierry.reding@gmail.com, hkallweit1@gmail.com, 
	linux-pwm@vger.kernel.org, linux-amlogic@lists.infradead.org, 
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel@salutedevices.com, 
	Dmitry Rokosov <ddrokosov@salutedevices.com>
Subject: Re: [PATCH v2 2/2] pwm: meson: Add check for error from
 clk_round_rate()
Message-ID: <xb2prc5ewslr74eh22xo4heeiepeiu4rb72zekuatcuhp45p6s@nhwhnq26tthg>
References: <20240424132408.2565916-1-gnstark@salutedevices.com>
 <20240424132408.2565916-3-gnstark@salutedevices.com>
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On Wed, Apr 24, 2024 at 04:24:08PM +0300, George Stark wrote:
> clk_round_rate() can return not only zero if requested frequency can not
> be provided but also negative error code so add check for it too.
>=20
> Also change type of variable holding clk_round_rate() result from
> unsigned long to long. It's safe due to clk_round_rate() returns long.
>=20
> Fixes: 329db102a26d ("pwm: meson: make full use of common clock framework=
")
> Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
> Signed-off-by: George Stark <gnstark@salutedevices.com>
> ---
>  drivers/pwm/pwm-meson.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>=20
> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
> index f4d70da621ec..d4228ac1e7ea 100644
> --- a/drivers/pwm/pwm-meson.c
> +++ b/drivers/pwm/pwm-meson.c
> @@ -148,7 +148,7 @@ static int meson_pwm_calc(struct pwm_chip *chip, stru=
ct pwm_device *pwm,
>  	struct meson_pwm *meson =3D to_meson_pwm(chip);
>  	struct meson_pwm_channel *channel =3D &meson->channels[pwm->hwpwm];
>  	unsigned int cnt, duty_cnt;
> -	unsigned long fin_freq;
> +	long fin_freq;
>  	u64 duty, period, freq;
> =20
>  	duty =3D state->duty_cycle;
> @@ -168,9 +168,10 @@ static int meson_pwm_calc(struct pwm_chip *chip, str=
uct pwm_device *pwm,
>  		freq =3D ULONG_MAX;
> =20
>  	fin_freq =3D clk_round_rate(channel->clk, freq);
> -	if (fin_freq =3D=3D 0) {
> -		dev_err(pwmchip_parent(chip), "invalid source clock frequency\n");
> -		return -EINVAL;
> +	if (fin_freq <=3D 0) {
> +		dev_err(pwmchip_parent(chip),
> +			"invalid source clock frequency %llu\n", freq);
> +		return fin_freq ? fin_freq : -EINVAL;
>  	}
> =20
>  	dev_dbg(pwmchip_parent(chip), "fin_freq: %lu Hz\n", fin_freq);
                                                   ^
With fin_freq now being unsigned, this ------------' should be a 'd'.

If you want to still extend your fixes series: A bit further below there
is

	cnt =3D div_u64(fin_freq * period, NSEC_PER_SEC);

=2E The multiplication there might overflow. This should better use
mul_u64_u64_div_u64() (or one of it's variants).

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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