From: Thierry Reding <thierry.reding@gmail.com>
To: Clemens Gruber <clemens.gruber@pqgruber.com>
Cc: linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-stable@vger.kernel.org,
Florian Vaussard <florian.vaussard@heig-vd.ch>,
Mika Westerberg <mika.westerberg@linux.intel.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: [PATCH 2/2] pwm: pca9685: fix prescaler initialization
Date: Wed, 18 Jan 2017 11:57:35 +0100 [thread overview]
Message-ID: <20170118105735.GM18989@ulmo.ba.sec> (raw)
In-Reply-To: <20161213155251.28684-2-clemens.gruber@pqgruber.com>
[-- Attachment #1: Type: text/plain, Size: 1995 bytes --]
On Tue, Dec 13, 2016 at 04:52:51PM +0100, Clemens Gruber wrote:
> Until now, we assumed that the period is the hardware default of 1/200Hz
> at probe time, but if the period was changed and the user reboots, this
> assumption is wrong.
>
> Solution: Check if the prescaler is set to the hardware default. If not,
> reprogram the prescaler at first configuration.
>
> Cc: <stable@vger.kernel.org> # v4.3+
> Signed-off-by: Clemens Gruber <clemens.gruber@pqgruber.com>
> ---
> drivers/pwm/pwm-pca9685.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
Cc'ing Mika and Andy and quoting verbatim for review.
Thierry
> diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
> index 01a6a83..efc657e 100644
> --- a/drivers/pwm/pwm-pca9685.c
> +++ b/drivers/pwm/pwm-pca9685.c
> @@ -55,6 +55,7 @@
> #define PCA9685_PRESCALE 0xFE
>
> #define PCA9685_PRESCALE_MIN 0x03 /* => max. frequency of 1526 Hz */
> +#define PCA9685_PRESCALE_DEF 0x1E /* => default frequency of 200 Hz */
> #define PCA9685_PRESCALE_MAX 0xFF /* => min. frequency of 24 Hz */
>
> #define PCA9685_COUNTER_RANGE 4096
> @@ -289,8 +290,8 @@ static int pca9685_pwm_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> struct pca9685 *pca;
> + int prescale, mode2;
> int ret;
> - int mode2;
>
> pca = devm_kzalloc(&client->dev, sizeof(*pca), GFP_KERNEL);
> if (!pca)
> @@ -304,10 +305,15 @@ static int pca9685_pwm_probe(struct i2c_client *client,
> return ret;
> }
> pca->duty_ns = 0;
> - pca->period_ns = PCA9685_DEFAULT_PERIOD;
>
> i2c_set_clientdata(client, pca);
>
> + regmap_read(pca->regmap, PCA9685_PRESCALE, &prescale);
> + if (prescale == PCA9685_PRESCALE_DEF)
> + pca->period_ns = PCA9685_DEFAULT_PERIOD;
> + else
> + pca->period_ns = 0;
> +
> regmap_read(pca->regmap, PCA9685_MODE2, &mode2);
>
> if (device_property_read_bool(&client->dev, "invert"))
> --
> 2.10.2
>
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
next prev parent reply other threads:[~2017-01-18 11:01 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-13 15:52 [PATCH 1/2] pwm: pca9685: fix period change with same duty cycle Clemens Gruber
2016-12-13 15:52 ` [PATCH 2/2] pwm: pca9685: fix prescaler initialization Clemens Gruber
2017-01-18 10:57 ` Thierry Reding [this message]
2017-01-18 11:09 ` Andy Shevchenko
2017-01-18 13:53 ` Clemens Gruber
2017-01-18 14:01 ` Andy Shevchenko
2017-01-18 14:25 ` Clemens Gruber
2017-01-19 12:34 ` Andy Shevchenko
2017-01-19 14:49 ` Clemens Gruber
2017-01-19 16:10 ` Andy Shevchenko
2017-01-19 16:52 ` Clemens Gruber
2017-01-19 16:58 ` Andy Shevchenko
2017-01-20 6:39 ` Thierry Reding
2017-01-20 9:58 ` Andy Shevchenko
2017-01-25 18:05 ` Clemens Gruber
2017-01-18 10:56 ` [PATCH 1/2] pwm: pca9685: fix period change with same duty cycle Thierry Reding
2017-01-18 11:09 ` Mika Westerberg
2017-01-20 6:44 ` Thierry Reding
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170118105735.GM18989@ulmo.ba.sec \
--to=thierry.reding@gmail.com \
--cc=andriy.shevchenko@linux.intel.com \
--cc=clemens.gruber@pqgruber.com \
--cc=florian.vaussard@heig-vd.ch \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pwm@vger.kernel.org \
--cc=linux-stable@vger.kernel.org \
--cc=mika.westerberg@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).