Received-SPF: pass (google.com: domain of linux-kernel+bounces-80934-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Mon, 26 Feb 2024 09:44:16 +0100
From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To: Leif Middelschulte <leif.middelschulte@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>, Sascha Hauer <s.hauer@pengutronix.de>, 
	Pengutronix Kernel Team <kernel@pengutronix.de>, Fabio Estevam <festevam@gmail.com>, 
	NXP Linux Team <linux-imx@nxp.com>, Leif Middelschulte <Leif.Middelschulte@klsmartin.com>, 
	linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pwm@vger.kernel.org
Subject: Re: [PATCH v4 1/2] pwm: imx27: fix race condition .apply,.get_state
Message-ID: <qucbpwau55tuaf5m5fqpsbub2bbtxcye4djxwrwkabssd2vc4j@weuiawrzbbnn>
References: <20230906154215.4ikrrbx4xgx2nmu5@pengutronix.de>
 <20240224112902.55539-1-Leif.Middelschulte@gmail.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
	protocol="application/pgp-signature"; boundary="gx6q65kgn6hbj44y"
Content-Disposition: inline
In-Reply-To: <20240224112902.55539-1-Leif.Middelschulte@gmail.com>


--gx6q65kgn6hbj44y
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

Hello,

On Sat, Feb 24, 2024 at 12:29:00PM +0100, Leif Middelschulte wrote:
> From: Leif Middelschulte <Leif.Middelschulte@klsmartin.com>
>=20
> With CONFIG_PWM_DEBUG=3Dy after writing a value to the PWMSAR
> register in .apply(), the register is read in .get_state().
> Unless a period completed in the meantime, this read yields the
> previously used duty cycle configuration. As the PWM_DEBUG code
> applies the read out configuration for testing purposes this
> effectively undoes the intended effect by rewriting the previous
> hardware state.
>=20
> Note that this change merely implements a sensible heuristic.
> The i.MX has a 4 slot FIFO to configure the duty cycle. This FIFO
> cannot be read back in its entirety. The "write x then read back
> x from hw" semantics are therefore not easily applicable.
> With this change, the .get_state() function tries to wait for some
> stabilization in the FIFO (empty state). In this state it keeps
> applying the last value written to the sample register.
>=20
> Signed-off-by: Leif Middelschulte <Leif.Middelschulte@klsmartin.com>

Another few things I noticed only after replying to this patch and
trying to apply #2:

 - Please make sure you have a S-o-b line for the sender (i.e. you with
   your gmail identity).
 - My reply to your klsmartin.com address couldn't be delivered, The MS
   mailserver told: "leif.middelschulte wasn't found at klsmartin.com."
 - Please start a new thread if you send a v5, as applying patches from
   a thread containing many patches is a bit less trivial.
 - Consider using git format-patch's --base parameter to document your
   patch base.

Best regards
Uwe

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

--gx6q65kgn6hbj44y
Content-Type: application/pgp-signature; name="signature.asc"

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

iQEzBAABCgAdFiEEP4GsaTp6HlmJrf7Tj4D7WH0S/k4FAmXcT18ACgkQj4D7WH0S
/k5/1AgAsv7GIPFu33eJYqefznjKB5CWEDraqN7l2mBgZ1sW9MPtWm9AvON87WET
0az+MsQVtH4wN1BcZa+3SgKY+Q1r56+FOaD3Y3GUdkEvEvIWLK+EQppYooHMaacK
IaS+hRJwoFqzrGjjzlqQRE5vXN0szSjgOn/zFYq0vfMsQohd8ibY+5SdtaBwfSlh
bTPt5MnqBCfzMEG9r9MVwZrdyojy3/BSgeutK5AKZr1KWsNQ3pwDm4414ChL2tVw
pjxRedvVYk6ThHO77XOxXzjrietgeh5D6Bg4r5wWwTrjENtK//h+843O8C0dCT6v
QnBgwigIWpRgcen7zPGO7VfclV8pQg==
=+JRg
-----END PGP SIGNATURE-----

--gx6q65kgn6hbj44y--