Date:   Fri, 3 Mar 2023 22:17:25 +0100
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     Lorenz Brun <lorenz@brun.one>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org
Subject: Re: [PATCH] pwm: mediatek: support inverted polarity
Message-ID: <20230303211725.7wtxdxjqpxlrp77b@pengutronix.de>
References: <20230303205821.2285418-1-lorenz@brun.one>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
        protocol="application/pgp-signature"; boundary="n7hf6kwnvue2vkyt"
Content-Disposition: inline
In-Reply-To: <20230303205821.2285418-1-lorenz@brun.one>
Precedence: bulk


--n7hf6kwnvue2vkyt
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Fri, Mar 03, 2023 at 09:58:21PM +0100, Lorenz Brun wrote:
> According to the MT7986 Reference Manual the Mediatek  PWM controller
> doesn't appear to have support for inverted polarity.
>=20
> This implements the same solution as in pwm-meson and just inverts the
> duty cycle instead, which results in the same outcome.

This idea is broken. This was recently discussed on the linux-pwm list
and I hope will be fixed soon. See
https://lore.kernel.org/linux-pwm/20230228093911.bh2sbp4tyfir2z5g@pengutron=
ix.de/T/#meda75ffbd4ef2048991ea2cd091c0c14b1bb09c2

So this patch won't be accepted, still pointing out a style problem
below.

> Signed-off-by: Lorenz Brun <lorenz@brun.one>
> ---
>  drivers/pwm/pwm-mediatek.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>=20
> diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
> index 5b5eeaff35da..6f4a54c8299f 100644
> --- a/drivers/pwm/pwm-mediatek.c
> +++ b/drivers/pwm/pwm-mediatek.c
> @@ -202,9 +202,7 @@ static int pwm_mediatek_apply(struct pwm_chip *chip, =
struct pwm_device *pwm,
>  			      const struct pwm_state *state)
>  {
>  	int err;
> -
> -	if (state->polarity !=3D PWM_POLARITY_NORMAL)
> -		return -EINVAL;
> +	u64 duty_cycle;
> =20
>  	if (!state->enabled) {
>  		if (pwm->state.enabled)
> @@ -213,7 +211,14 @@ static int pwm_mediatek_apply(struct pwm_chip *chip,=
 struct pwm_device *pwm,
>  		return 0;
>  	}
> =20
> -	err =3D pwm_mediatek_config(pwm->chip, pwm, state->duty_cycle, state->p=
eriod);
> +	// According to the MT7986 Reference Manual the peripheral does not
> +	// appear to have the capability to invert the output. Instead just
> +	// invert the duty cycle.

Wrong commenting style, please stick to C-style comments (/* ... */)

> +	duty_cycle =3D state->duty_cycle;
> +	if (state->polarity =3D=3D PWM_POLARITY_INVERSED)
> +		duty_cycle =3D state->period - state->duty_cycle;
> +
> +	err =3D pwm_mediatek_config(pwm->chip, pwm, duty_cycle, state->period);
>  	if (err)
>  		return err;

Best regards
Uwe

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

--n7hf6kwnvue2vkyt
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iQEzBAABCgAdFiEEfnIqFpAYrP8+dKQLwfwUeK3K7AkFAmQCY+IACgkQwfwUeK3K
7An4QAf/VVzJ1G1vLm5fgqHWXuxXbRYDJjva5NFicH4hK041/2hnM4z6BbR6dAI1
YvBRLNTRTj6Wacfz19kTKht1KUHyJFo+0rXvm7OTVE2Kk+QonHuoWWDxkEYphlhG
IYbl7xuHl42c4cQ2qyA2+j4pItly7UrZVEwm20UGTgEf04V3pZdjhtZ41BOMk/mN
m4XRjJMwp/UURdNcj1D1a0LptvzNdqohH8t8y5RtIV8m6IRH2BdCyJsWi3iRyWNp
A748CqKSRhN1gj1ow0zPZO+nNQ4N91ZAb6AM3PLnaUoL+r69lG3355uaj/5H6bjW
ovEzhU8TABbvhEVdstiMVHpOulLcDg==
=6bfG
-----END PGP SIGNATURE-----

--n7hf6kwnvue2vkyt--