The Netronix EC provides a PWM output, which is used for the backlight
on ebook readers. This patches adds a driver for the PWM output.
Signed-off-by: Jonathan Neuschäfer <[email protected]>
---
drivers/pwm/Kconfig | 4 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-ntxec.c | 148 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 153 insertions(+)
create mode 100644 drivers/pwm/pwm-ntxec.c
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index cb8d739067d2f..147d6629e662c 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -350,6 +350,10 @@ config PWM_MXS
To compile this driver as a module, choose M here: the module
will be called pwm-mxs.
+config PWM_NTXEC
+ tristate "Netronix embedded controller PWM support"
+ depends on MFD_NTXEC && OF
+
config PWM_OMAP_DMTIMER
tristate "OMAP Dual-Mode Timer PWM support"
depends on OF
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index a59c710e98c76..15507a6d9ca12 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_PWM_MESON) += pwm-meson.o
obj-$(CONFIG_PWM_MEDIATEK) += pwm-mediatek.o
obj-$(CONFIG_PWM_MTK_DISP) += pwm-mtk-disp.o
obj-$(CONFIG_PWM_MXS) += pwm-mxs.o
+obj-$(CONFIG_PWM_NTXEC) += pwm-ntxec.o
obj-$(CONFIG_PWM_OMAP_DMTIMER) += pwm-omap-dmtimer.o
obj-$(CONFIG_PWM_PCA9685) += pwm-pca9685.o
obj-$(CONFIG_PWM_PUV3) += pwm-puv3.o
diff --git a/drivers/pwm/pwm-ntxec.c b/drivers/pwm/pwm-ntxec.c
new file mode 100644
index 0000000000000..eca305d8e915b
--- /dev/null
+++ b/drivers/pwm/pwm-ntxec.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright 2020 Jonathan Neuschäfer <[email protected]>
+//
+// PWM driver for Netronix embedded controller.
+
+#include <linux/mfd/ntxec.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/of_device.h>
+#include <linux/types.h>
+
+struct ntxec_pwm {
+ struct device *dev;
+ struct ntxec *ec;
+ struct pwm_chip chip;
+};
+
+static struct ntxec_pwm *pwmchip_to_pwm(struct pwm_chip *chip)
+{
+ return container_of(chip, struct ntxec_pwm, chip);
+}
+
+#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;
+ int res = 0;
+
+ do_div(period, 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;
+ }
+
+ 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);
+
+ 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,
+};
+
+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;
+}
+
+static int ntxec_pwm_remove(struct platform_device *pdev)
+{
+ struct ntxec_pwm *pwm = platform_get_drvdata(pdev);
+ struct pwm_chip *chip = &pwm->chip;
+
+ return pwmchip_remove(chip);
+}
+
+static const struct of_device_id ntxec_pwm_of_match[] = {
+ { .compatible = "netronix,ntxec-pwm" },
+ { },
+};
+MODULE_DEVICE_TABLE(of, ntxec_pwm_of_match);
+
+static struct platform_driver ntxec_pwm_driver = {
+ .driver = {
+ .name = "ntxec-pwm",
+ .of_match_table = ntxec_pwm_of_match,
+ },
+ .probe = ntxec_pwm_probe,
+ .remove = ntxec_pwm_remove,
+};
+module_platform_driver(ntxec_pwm_driver);
+
+MODULE_AUTHOR("Jonathan Neuschäfer <[email protected]>");
+MODULE_DESCRIPTION("PWM driver for Netronix EC");
+MODULE_LICENSE("GPL");
--
2.27.0
Hello,
On Sun, Jun 21, 2020 at 12:42:17AM +0200, Jonathan Neusch?fer 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-K?nig |
Industrial Linux Solutions | https://www.pengutronix.de/ |
On Mon, Jun 22, 2020 at 10:18:02AM +0200, Uwe Kleine-König wrote:
> 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
Ok, I'll fix these.
>
> > +#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.
No particular reason; I possibly got confused by the division API. I'll
use uint32_t instead.
> > + int res = 0;
> > +
> > + do_div(period, 125);
>
> Please use a define instead of plain 125.
Will do.
> > + 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.
Ok, I'll remove it.
>
> > + 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?
Good question. I haven't measured it, and also don't have the code
running on the EC.
>
> > +
> > + 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.
Ok
> 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.
Will do!
>
> > +};
> > +
> > +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.
Ok, I'll rework the probe function to avoid these issues.
Thanks for the review,
Jonathan Neuschäfer