Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753047AbdGFIBj (ORCPT ); Thu, 6 Jul 2017 04:01:39 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:34550 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753002AbdGFIBh (ORCPT ); Thu, 6 Jul 2017 04:01:37 -0400 Date: Thu, 6 Jul 2017 10:01:32 +0200 From: Thierry Reding To: Enric Balletbo i Serra Cc: Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz , Rob Herring , Pavel Machek , 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: <20170706080132.GL16144@ulmo.fritz.box> References: <20170630112109.13785-1-enric.balletbo@collabora.com> <20170630112109.13785-2-enric.balletbo@collabora.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="1hKfHPzOXWu1rh0v" Content-Disposition: inline In-Reply-To: <20170630112109.13785-2-enric.balletbo@collabora.com> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4725 Lines: 140 --1hKfHPzOXWu1rh0v Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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 panel > 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. 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. Two more comments below. > 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/p= wm_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_data= *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); 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: usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2); ? > + > 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_dat= a *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 *dev, > data->max_brightness--; > } > =20 > + /* read pwm to enable pre/post delays from DT property */ This comment is confusing. This isn't reading anything from the PWM. Thierry --1hKfHPzOXWu1rh0v Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAlld7lkACgkQ3SOs138+ s6ESkQ//Q9KgkEjoCjIx+nZN0oSuEYZOEXCTlP+NNNwuklxz8mVnvf1lwsIGKtjG UI1U+ukCT+aky88yVfLYMCZ7+OQUQ2m9FWPIPPSG3tzGpwYdfQ4l3dD73Bm7Xp3l hGOf9n8YzzoObSeYabi7O/JsWj0cSumcSz30uiiv+wRffXrPKF6qHTK7pm0+DKC3 dGUKvbh+HmZ2N8xvBizIYNOJn5BRLjUzpVmeE+Zg9sL7SO3GHXxMpc1xvhNejnu2 Q4OmEIbGoTIxdwuQc87IBpqUU0/IEdC+eMH1OugQW9Jyah2dD5Vsirw+enWMv5r9 zSrDetASIDQIafXhiXUC8rtjJDnH3+tPeRDHd4UDeCXUMTlnG541vO+ziL4rOO7z rf6AXWlDnG+LQCpmy5YD8tqFPxSQj7NfYQQ1CwCwYCuGPrlulQJ4x8r0jO/HkQ6B PhxMiun8zjRKj7itzJeZII7gJT1rLvDLUfwCFzbMz6gfnPzwD34A2a/EQrbBNI6G P8gBGp9cuGaKeSF7mjcHGPRk8LuRSUVtNxOOwNrCF/fykinaGnFfsx0eF9vcFWFd ol9Y+lE8UsYmMZvJp0NBDXUMrNbAX+UfsDKLTUdvwvzTb6v687m+0TkaXyju062R iFw259hcgEHu+FHKqA3J0nKeWYppvQosq8HJwKlGcObVVpkoqhc= =C0A3 -----END PGP SIGNATURE----- --1hKfHPzOXWu1rh0v--