Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752483AbdGFJMr (ORCPT ); Thu, 6 Jul 2017 05:12:47 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:54356 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750998AbdGFJMp (ORCPT ); Thu, 6 Jul 2017 05:12:45 -0400 Date: Thu, 6 Jul 2017 11:12:31 +0200 From: Pavel Machek To: Thierry Reding Cc: Enric Balletbo i Serra , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz , Rob Herring , Richard Purdie , Jacek Anaszewski , Heiko Stuebner , linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, groeck@chromium.org, linux-rockchip@lists.infradead.org, huang lin Subject: Re: [PATCH v2 2/4] pwm-backlight: add support for pwm-delay-us property Message-ID: <20170706091231.GA6741@amd> References: <20170630112109.13785-1-enric.balletbo@collabora.com> <20170630112109.13785-2-enric.balletbo@collabora.com> <20170706080132.GL16144@ulmo.fritz.box> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="EVF5PPMfhYS0aIcm" Content-Disposition: inline In-Reply-To: <20170706080132.GL16144@ulmo.fritz.box> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4631 Lines: 146 --EVF5PPMfhYS0aIcm Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu 2017-07-06 10:01:32, Thierry Reding wrote: > On Fri, Jun 30, 2017 at 01:21:07PM +0200, Enric Balletbo i Serra wrote: > > From: huang lin > >=20 > > Some panels (i.e. N116BGE-L41), in their power sequence specifications, > > request a delay between set the PWM signal and enable the backlight and > > between clear the PWM signal and disable the backlight. Add support for > > the new pwm-delay-us property to meet the timing. > >=20 > > Note that this patch inverts current sequence. Before this patch the > > enable signal was set before the PWM signal and vice-versa on power off. > >=20 > > I assumed that this sequence was wrong, at least it is on different pan= el > > datasheets that I checked, so I inverted the sequence to follow: > >=20 > > On power on, set the PWM signal, wait, and set the LED_EN signal. > > On power off, clear the LED_EN signal, wait, and stop the PWM signal. >=20 > I think this should be two separate patches to make it easier to revert > the inverted sequence should it prove to regress on other panels. Don't make this overly complex. This is trivial. No need to split it into more patches. > Two more comments below. >=20 > > Signed-off-by: huang lin > > Signed-off-by: Enric Balletbo i Serra > > --- > > Changes since v1: > > - As suggested by Daniel Thompson > > - Do not assume power-on delay and power-off delay will be the same > > - Move the check of dt property to the parse dt function. > >=20 > > v1: https://lkml.org/lkml/2017/6/28/219 > >=20 > > drivers/video/backlight/pwm_bl.c | 24 ++++++++++++++++++++---- > > include/linux/pwm_backlight.h | 1 + > > 2 files changed, 21 insertions(+), 4 deletions(-) > >=20 > > diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight= /pwm_bl.c > > index 002f1ce..0f5470e 100644 > > --- a/drivers/video/backlight/pwm_bl.c > > +++ b/drivers/video/backlight/pwm_bl.c > > @@ -10,6 +10,7 @@ > > * published by the Free Software Foundation. > > */ > > =20 > > +#include > > #include > > #include > > #include > > @@ -35,6 +36,7 @@ struct pwm_bl_data { > > struct gpio_desc *enable_gpio; > > unsigned int scale; > > bool legacy; > > + unsigned int pwm_delay[2]; > > int (*notify)(struct device *, > > int brightness); > > void (*notify_after)(struct device *, > > @@ -54,10 +56,14 @@ static void pwm_backlight_power_on(struct pwm_bl_da= ta *pb, int brightness) > > if (err < 0) > > dev_err(pb->dev, "failed to enable power supply\n"); > > =20 > > + pwm_enable(pb->pwm); > > + > > + if (pb->pwm_delay[0]) > > + usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] + 2000); >=20 > 2000 us is kind of arbitrary. What if pwm_delay[0] is on the order of 20 > us? Making the delay 2 ms longer (in the worst case) seems somewhat > excessive. Why not something like: >=20 > usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2); >=20 > ? >=20 > > + > > if (pb->enable_gpio) > > gpiod_set_value_cansleep(pb->enable_gpio, 1); > > =20 > > - pwm_enable(pb->pwm); > > pb->enabled =3D true; > > } > > =20 > > @@ -66,12 +72,15 @@ static void pwm_backlight_power_off(struct pwm_bl_d= ata *pb) > > if (!pb->enabled) > > return; > > =20 > > - pwm_config(pb->pwm, 0, pb->period); > > - pwm_disable(pb->pwm); > > - > > if (pb->enable_gpio) > > gpiod_set_value_cansleep(pb->enable_gpio, 0); > > =20 > > + if (pb->pwm_delay[1]) > > + usleep_range(pb->pwm_delay[1], pb->pwm_delay[1] + 2000); > > + > > + pwm_config(pb->pwm, 0, pb->period); > > + pwm_disable(pb->pwm); > > + > > regulator_disable(pb->power_supply); > > pb->enabled =3D false; > > } > > @@ -174,6 +183,12 @@ static int pwm_backlight_parse_dt(struct device *d= ev, > > data->max_brightness--; > > } > > =20 > > + /* read pwm to enable pre/post delays from DT property */ >=20 > This comment is confusing. This isn't reading anything from the PWM. >=20 > Thierry --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --EVF5PPMfhYS0aIcm Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlld/v8ACgkQMOfwapXb+vIGFwCZAa+++mSKuT2Ho8cB3raXQIEH tfIAnRbHsibYYGJeGe4hXOfXeGf0O2u6 =2RLI -----END PGP SIGNATURE----- --EVF5PPMfhYS0aIcm--