From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: "Jonathan Neuschäfer" <j.neuschaefer@gmx.net>
Cc: linux-kernel@vger.kernel.org,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Heiko Stuebner <heiko@sntech.de>,
linux-pwm@vger.kernel.org,
Linus Walleij <linus.walleij@linaro.org>,
Thierry Reding <thierry.reding@gmail.com>,
Fabio Estevam <festevam@gmail.com>,
linux-rtc@vger.kernel.org,
Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
Sam Ravnborg <sam@ravnborg.org>,
Andreas Kemnade <andreas@kemnade.info>,
NXP Linux Team <linux-imx@nxp.com>,
devicetree@vger.kernel.org, Stephan Gerhold <stephan@gerhold.net>,
allen <allen.chen@ite.com.tw>,
Sascha Hauer <s.hauer@pengutronix.de>,
Lubomir Rintel <lkundrak@v3.sk>, Rob Herring <robh+dt@kernel.org>,
Lee Jones <lee.jones@linaro.org>,
linux-arm-kernel@lists.infradead.org,
Alessandro Zummo <a.zummo@towertech.it>,
Mark Brown <broonie@kernel.org>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Heiko Stuebner <heiko.stuebner@theobroma-systems.com>,
Josua Mayer <josua.mayer@jm0.eu>, Shawn Guo <shawnguo@kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [RFC PATCH 06/10] pwm: ntxec: Add driver for PWM function in Netronix EC
Date: Mon, 22 Jun 2020 10:18:02 +0200 [thread overview]
Message-ID: <20200622081802.pv4xmb7vn4te5r5t@taurus.defre.kleine-koenig.org> (raw)
In-Reply-To: <20200620224222.1312520-5-j.neuschaefer@gmx.net>
[-- Attachment #1: Type: text/plain, Size: 4065 bytes --]
Hello,
On Sun, Jun 21, 2020 at 12:42:17AM +0200, Jonathan Neuschäfer wrote:
> The Netronix EC provides a PWM output, which is used for the backlight
s/,//
> on ebook readers. This patches adds a driver for the PWM output.
on *some* ebook readers
> +#define NTXEC_UNK_A 0xa1
> +#define NTXEC_UNK_B 0xa2
> +#define NTXEC_ENABLE 0xa3
> +#define NTXEC_PERIOD_LOW 0xa4
> +#define NTXEC_PERIOD_HIGH 0xa5
> +#define NTXEC_DUTY_LOW 0xa6
> +#define NTXEC_DUTY_HIGH 0xa7
> +
> +/*
> + * The time base used in the EC is 8MHz, or 125ns. Period and duty cycle are
> + * measured in this unit.
> + */
> +static int ntxec_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm_dev,
> + int duty_ns, int period_ns)
> +{
> + struct ntxec_pwm *pwm = pwmchip_to_pwm(chip);
> + uint64_t duty = duty_ns;
> + uint64_t period = period_ns;
As you cannot use values bigger than 8191999 anyhow, I wonder why you
use a 64 bit type here.
> + int res = 0;
> +
> + do_div(period, 125);
Please use a define instead of plain 125.
> + if (period > 0xffff) {
> + dev_warn(pwm->dev,
> + "Period is not representable in 16 bits: %llu\n", period);
> + return -ERANGE;
> + }
> +
> + do_div(duty, 125);
> + if (duty > 0xffff) {
> + dev_warn(pwm->dev, "Duty cycle is not representable in 16 bits: %llu\n",
> + duty);
> + return -ERANGE;
> + }
This check isn't necessary as the pwm core ensures that duty <= period.
> + res |= ntxec_write8(pwm->ec, NTXEC_PERIOD_HIGH, period >> 8);
> + res |= ntxec_write8(pwm->ec, NTXEC_PERIOD_LOW, period);
> + res |= ntxec_write8(pwm->ec, NTXEC_DUTY_HIGH, duty >> 8);
> + res |= ntxec_write8(pwm->ec, NTXEC_DUTY_LOW, duty);
Does this complete the currently running period? Can it happen that a
new period starts between the first and the last write and so a mixed
period can be seen at the output?
> +
> + return (res < 0) ? -EIO : 0;
> +}
> +
> +static int ntxec_pwm_enable(struct pwm_chip *chip,
> + struct pwm_device *pwm_dev)
> +{
> + struct ntxec_pwm *pwm = pwmchip_to_pwm(chip);
> +
> + return ntxec_write8(pwm->ec, NTXEC_ENABLE, 1);
> +}
> +
> +static void ntxec_pwm_disable(struct pwm_chip *chip,
> + struct pwm_device *pwm_dev)
> +{
> + struct ntxec_pwm *pwm = pwmchip_to_pwm(chip);
> +
> + ntxec_write8(pwm->ec, NTXEC_ENABLE, 0);
> +}
> +
> +static struct pwm_ops ntxec_pwm_ops = {
> + .config = ntxec_pwm_config,
> + .enable = ntxec_pwm_enable,
> + .disable = ntxec_pwm_disable,
> + .owner = THIS_MODULE,
Please don't align the =, just a single space before them is fine.
More important: Please implement .apply() (and .get_state()) instead of
the old API. Also please enable PWM_DEBUG which might save us a review
iteration.
> +};
> +
> +static int ntxec_pwm_probe(struct platform_device *pdev)
> +{
> + struct ntxec *ec = dev_get_drvdata(pdev->dev.parent);
> + struct ntxec_pwm *pwm;
> + struct pwm_chip *chip;
> + int res;
> +
> + pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
> + if (!pwm)
> + return -ENOMEM;
> +
> + pwm->ec = ec;
> + pwm->dev = &pdev->dev;
> +
> + chip = &pwm->chip;
> + chip->dev = &pdev->dev;
> + chip->ops = &ntxec_pwm_ops;
> + chip->base = -1;
> + chip->npwm = 1;
> +
> + res = pwmchip_add(chip);
> + if (res < 0)
> + return res;
> +
> + platform_set_drvdata(pdev, pwm);
> +
> + res |= ntxec_write8(pwm->ec, NTXEC_ENABLE, 0);
> + res |= ntxec_write8(pwm->ec, NTXEC_UNK_A, 0xff);
> + res |= ntxec_write8(pwm->ec, NTXEC_UNK_B, 0xff);
> +
> + return (res < 0) ? -EIO : 0;
This is broken for several reasons:
- You're not supposed to modify the output in .probe
- if ntxec_write8 results in an error you keep the pwm registered.
- From the moment on pwmchip_add returns the callbacks can be called.
The calls to ntxec_write8 probably interfere here.
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:[~2020-06-22 8:18 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-20 22:42 [RFC PATCH 02/10] dt-bindings: Add vendor prefix for Netronix, Inc Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 03/10] dt-bindings: mfd: Add binding for Netronix's embedded controller Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 04/10] mfd: Add base driver for Netronix " Jonathan Neuschäfer
2020-06-22 10:55 ` Lee Jones
2020-06-28 8:11 ` Jonathan Neuschäfer
2020-06-27 8:17 ` Andreas Kemnade
2020-06-28 8:29 ` Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 05/10] dt-bindings: pwm: Add bindings for PWM function in Netronix EC Jonathan Neuschäfer
2020-06-21 18:41 ` Andreas Kemnade
2020-08-23 22:42 ` Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 06/10] pwm: ntxec: Add driver " Jonathan Neuschäfer
2020-06-22 8:18 ` Uwe Kleine-König [this message]
2020-07-03 16:15 ` Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 07/10] dt-bindings: rtc: Add bindings for Netronix embedded controller RTC Jonathan Neuschäfer
2020-06-21 0:02 ` Alexandre Belloni
2020-06-26 21:55 ` Andreas Kemnade
2020-07-03 17:04 ` Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 08/10] rtc: New driver for RTC in Netronix embedded controller Jonathan Neuschäfer
2020-06-21 0:11 ` Alexandre Belloni
2020-07-04 19:23 ` Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 09/10] MAINTAINERS: Add entry for " Jonathan Neuschäfer
2020-06-20 22:42 ` [RFC PATCH 10/10] ARM: dts: imx50-kobo-aura: Add " Jonathan Neuschäfer
2020-06-20 22:46 ` [RFC PATCH 02/10] dt-bindings: Add vendor prefix for Netronix, Inc Jonathan Neuschäfer
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=20200622081802.pv4xmb7vn4te5r5t@taurus.defre.kleine-koenig.org \
--to=u.kleine-koenig@pengutronix.de \
--cc=a.zummo@towertech.it \
--cc=alexandre.belloni@bootlin.com \
--cc=allen.chen@ite.com.tw \
--cc=andreas@kemnade.info \
--cc=broonie@kernel.org \
--cc=davem@davemloft.net \
--cc=devicetree@vger.kernel.org \
--cc=festevam@gmail.com \
--cc=heiko.stuebner@theobroma-systems.com \
--cc=heiko@sntech.de \
--cc=j.neuschaefer@gmx.net \
--cc=josua.mayer@jm0.eu \
--cc=kernel@pengutronix.de \
--cc=lee.jones@linaro.org \
--cc=linus.walleij@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-imx@nxp.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pwm@vger.kernel.org \
--cc=linux-rtc@vger.kernel.org \
--cc=lkundrak@v3.sk \
--cc=mchehab+huawei@kernel.org \
--cc=robh+dt@kernel.org \
--cc=s.hauer@pengutronix.de \
--cc=sam@ravnborg.org \
--cc=shawnguo@kernel.org \
--cc=stephan@gerhold.net \
--cc=thierry.reding@gmail.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).