From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Baruch Siach <baruch@tkos.co.il>
Cc: Thierry Reding <thierry.reding@gmail.com>,
Lee Jones <lee.jones@linaro.org>,
Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Russell King <linux@armlinux.org.uk>,
Andrew Lunn <andrew@lunn.ch>,
Gregory Clement <gregory.clement@bootlin.com>,
Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Chris Packham <chris.packham@alliedtelesis.co.nz>,
Sascha Hauer <s.hauer@pengutronix.de>,
Ralph Sennhauser <ralph.sennhauser@gmail.com>,
linux-pwm@vger.kernel.org, linux-gpio@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 5/5] gpio: mvebu: document zero pwm duty cycle limitation
Date: Thu, 14 Jan 2021 21:25:45 +0100 [thread overview]
Message-ID: <20210114202545.7wnc5ikeffc45xk5@pengutronix.de> (raw)
In-Reply-To: <7c18dd67d3bf3e3ed9a8efa2edd33e8f29f09a7a.1610628807.git.baruch@tkos.co.il>
[-- Attachment #1: Type: text/plain, Size: 1224 bytes --]
Hello Baruch,
On Thu, Jan 14, 2021 at 08:57:37PM +0200, Baruch Siach wrote:
> Add a comment on why the code never sets on/off registers to zero.
>
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Analyzed-by: Russell King <linux@armlinux.org.uk>
> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
> ---
> drivers/gpio/gpio-mvebu.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
> index 6b017854ce61..09780944bef9 100644
> --- a/drivers/gpio/gpio-mvebu.c
> +++ b/drivers/gpio/gpio-mvebu.c
> @@ -706,6 +706,10 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> do_div(val, NSEC_PER_SEC);
> if (val > UINT_MAX)
> return -EINVAL;
> + /*
> + * Zero on/off values don't work as expected. Experimentation shows
> + * that zero value is treated as 2^32. This behavior is not documented.
> + */
This is too easy. The right thing to do is to adapt .apply and
.get_state to use this new information.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
next prev parent reply other threads:[~2021-01-14 20:27 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 18:57 [PATCH v3 0/5] gpio: mvebu: pwm fixes and improvements Baruch Siach
2021-01-14 18:57 ` [PATCH v3 1/5] gpio: mvebu: fix pwm .get_state period calculation Baruch Siach
2021-01-14 18:57 ` [PATCH v3 2/5] gpio: mvebu: improve pwm period calculation accuracy Baruch Siach
2021-01-14 18:57 ` [PATCH v3 3/5] gpio: mvebu: make pwm .get_state closer to idempotent Baruch Siach
2021-01-14 18:57 ` [PATCH v3 4/5] gpio: mvebu: don't limit pwm period/duty_cycle to UINT_MAX Baruch Siach
2021-01-14 18:57 ` [PATCH v3 5/5] gpio: mvebu: document zero pwm duty cycle limitation Baruch Siach
2021-01-14 20:25 ` Uwe Kleine-König [this message]
2021-01-14 22:28 ` Russell King - ARM Linux admin
2021-01-15 10:53 ` Uwe Kleine-König
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=20210114202545.7wnc5ikeffc45xk5@pengutronix.de \
--to=u.kleine-koenig@pengutronix.de \
--cc=andrew@lunn.ch \
--cc=baruch@tkos.co.il \
--cc=bgolaszewski@baylibre.com \
--cc=chris.packham@alliedtelesis.co.nz \
--cc=gregory.clement@bootlin.com \
--cc=lee.jones@linaro.org \
--cc=linus.walleij@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-gpio@vger.kernel.org \
--cc=linux-pwm@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=ralph.sennhauser@gmail.com \
--cc=s.hauer@pengutronix.de \
--cc=sebastian.hesselbarth@gmail.com \
--cc=thierry.reding@gmail.com \
--cc=thomas.petazzoni@bootlin.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).