From: "Jonathan Neuschäfer" <j.neuschaefer@gmx.net>
To: linux-kernel@vger.kernel.org
Cc: "Lee Jones" <lee.jones@linaro.org>,
"Rob Herring" <robh+dt@kernel.org>,
"Jonathan Neuschäfer" <j.neuschaefer@gmx.net>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Alessandro Zummo" <a.zummo@towertech.it>,
"Alexandre Belloni" <alexandre.belloni@bootlin.com>,
"Shawn Guo" <shawnguo@kernel.org>,
"Sascha Hauer" <s.hauer@pengutronix.de>,
"Pengutronix Kernel Team" <kernel@pengutronix.de>,
"Fabio Estevam" <festevam@gmail.com>,
"NXP Linux Team" <linux-imx@nxp.com>,
"Sam Ravnborg" <sam@ravnborg.org>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Heiko Stuebner" <heiko.stuebner@theobroma-systems.com>,
"Stephan Gerhold" <stephan@gerhold.net>,
"Lubomir Rintel" <lkundrak@v3.sk>,
"Mark Brown" <broonie@kernel.org>, allen <allen.chen@ite.com.tw>,
"Mauro Carvalho Chehab" <mchehab+huawei@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
devicetree@vger.kernel.org, linux-pwm@vger.kernel.org,
linux-rtc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
"Heiko Stuebner" <heiko@sntech.de>,
"Josua Mayer" <josua.mayer@jm0.eu>,
"Andreas Kemnade" <andreas@kemnade.info>,
"Arnd Bergmann" <arnd@arndb.de>,
"Daniel Palmer" <daniel@0x0f.com>
Subject: [PATCH v2 05/10] pwm: ntxec: Add driver for PWM function in Netronix EC
Date: Sat, 5 Sep 2020 15:32:25 +0200 [thread overview]
Message-ID: <20200905133230.1014581-6-j.neuschaefer@gmx.net> (raw)
In-Reply-To: <20200905133230.1014581-1-j.neuschaefer@gmx.net>
The Netronix EC provides a PWM output which is used for the backlight
on some ebook readers. This patches adds a driver for the PWM output.
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
---
v2:
- Various grammar and style improvements, as suggested by Uwe Kleine-König,
Lee Jones, and Alexandre Belloni
- Switch to regmap
- Prefix registers with NTXEC_REG_
- Add help text to the Kconfig option
- Use the .apply callback instead of the old API
- Add a #define for the time base (125ns)
- Don't change device state in .probe; this avoids multiple problems
- Rework division and overflow check logic to perform divisions in 32 bits
- Avoid setting duty cycle to zero, to work around a hardware quirk
---
drivers/pwm/Kconfig | 8 ++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwm-ntxec.c | 160 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 169 insertions(+)
create mode 100644 drivers/pwm/pwm-ntxec.c
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 7dbcf6973d335..7fd17c6cda95e 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -350,6 +350,14 @@ 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
+ help
+ Say yes here if you want to support the PWM output of the embedded
+ controller found in certain e-book readers designed by the ODM
+ Netronix.
+
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 2c2ba0a035577..1cc50dba22d1b 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_PXA) += pwm-pxa.o
diff --git a/drivers/pwm/pwm-ntxec.c b/drivers/pwm/pwm-ntxec.c
new file mode 100644
index 0000000000000..325ec0e8f1996
--- /dev/null
+++ b/drivers/pwm/pwm-ntxec.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * The Netronix embedded controller is a microcontroller found in some
+ * e-book readers designed by the ODM Netronix, Inc. It contains RTC,
+ * battery monitoring, system power management, and PWM functionality.
+ *
+ * This driver implements PWM output.
+ *
+ * Copyright 2020 Jonathan Neuschäfer
+ */
+
+#include <linux/mfd/ntxec.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.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_REG_AUTO_OFF_HI 0xa1
+#define NTXEC_REG_AUTO_OFF_LO 0xa2
+#define NTXEC_REG_ENABLE 0xa3
+#define NTXEC_REG_PERIOD_LOW 0xa4
+#define NTXEC_REG_PERIOD_HIGH 0xa5
+#define NTXEC_REG_DUTY_LOW 0xa6
+#define NTXEC_REG_DUTY_HIGH 0xa7
+
+/* Convert an 8-bit value into the correct format for writing into a register */
+#define u8_to_reg(x) (((x) & 0xff) << 8)
+
+/*
+ * The time base used in the EC is 8MHz, or 125ns. Period and duty cycle are
+ * measured in this unit.
+ */
+#define TIME_BASE_NS 125
+
+/*
+ * The maximum input value (in nanoseconds) is determined by the time base and
+ * the range of the hardware registers that hold the converted value.
+ * It fits into 32 bits, so we can do our calculations in 32 bits as well.
+ */
+#define MAX_PERIOD_NS (TIME_BASE_NS * 0x10000 - 1)
+
+static int ntxec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm_dev,
+ const struct pwm_state *state)
+{
+ struct ntxec_pwm *pwm = pwmchip_to_pwm(pwm_dev->chip);
+ unsigned int duty = state->duty_cycle;
+ unsigned int period = state->period;
+ int res = 0;
+
+ if (period > MAX_PERIOD_NS) {
+ dev_warn(pwm->dev,
+ "Period is not representable in 16 bits after division by %u: %u\n",
+ TIME_BASE_NS, period);
+ return -ERANGE;
+ }
+
+ period /= TIME_BASE_NS;
+ duty /= TIME_BASE_NS;
+
+ res |= regmap_write(pwm->ec->regmap, NTXEC_REG_PERIOD_HIGH, u8_to_reg(period >> 8));
+ res |= regmap_write(pwm->ec->regmap, NTXEC_REG_PERIOD_LOW, u8_to_reg(period));
+ res |= regmap_write(pwm->ec->regmap, NTXEC_REG_DUTY_HIGH, u8_to_reg(duty >> 8));
+ res |= regmap_write(pwm->ec->regmap, NTXEC_REG_DUTY_LOW, u8_to_reg(duty));
+
+ if (res < 0)
+ return -EIO;
+
+ /*
+ * Writing a duty cycle of zone puts the device into a state where
+ * writing a higher duty cycle doesn't result in the brightness that it
+ * usually results in. This can be fixed by cycling the ENABLE register.
+ *
+ * As a workaround, write ENABLE=0 when the duty cycle is zero.
+ */
+ if (state->enabled && duty != 0) {
+ res |= regmap_write(pwm->ec->regmap, NTXEC_REG_ENABLE, u8_to_reg(1));
+
+ /* Disable the auto-off timer */
+ res |= regmap_write(pwm->ec->regmap, NTXEC_REG_AUTO_OFF_HI, u8_to_reg(0xff));
+ res |= regmap_write(pwm->ec->regmap, NTXEC_REG_AUTO_OFF_LO, u8_to_reg(0xff));
+ return res ? -EIO : 0;
+ } else {
+ return regmap_write(pwm->ec->regmap, NTXEC_REG_ENABLE, u8_to_reg(0));
+ }
+}
+
+static struct pwm_ops ntxec_pwm_ops = {
+ .apply = ntxec_pwm_apply,
+ .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);
+
+ 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 <j.neuschaefer@gmx.net>");
+MODULE_DESCRIPTION("PWM driver for Netronix EC");
+MODULE_LICENSE("GPL");
--
2.28.0
next prev parent reply other threads:[~2020-09-05 13:52 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-05 13:32 [PATCH v2 00/10] Netronix embedded controller driver for Kobo and Tolino ebook readers Jonathan Neuschäfer
2020-09-05 13:32 ` [PATCH v2 01/10] dt-bindings: Add vendor prefix for Netronix, Inc Jonathan Neuschäfer
2020-09-15 0:43 ` Rob Herring
2020-09-05 13:32 ` [PATCH v2 02/10] dt-bindings: mfd: Add binding for Netronix's embedded controller Jonathan Neuschäfer
2020-09-15 0:50 ` Rob Herring
2020-09-17 11:12 ` Jonathan Neuschäfer
2020-09-05 13:32 ` [PATCH v2 03/10] mfd: Add base driver for Netronix " Jonathan Neuschäfer
2020-09-08 13:29 ` Lee Jones
2020-09-10 12:04 ` Jonathan Neuschäfer
2020-09-05 13:32 ` [PATCH v2 04/10] dt-bindings: pwm: Add bindings for PWM function in Netronix EC Jonathan Neuschäfer
2020-09-15 0:54 ` Rob Herring
2020-09-15 6:23 ` Andreas Kemnade
2020-09-15 14:31 ` Rob Herring
2020-09-17 11:58 ` Jonathan Neuschäfer
2020-09-05 13:32 ` Jonathan Neuschäfer [this message]
[not found] ` <CAHp75VdUHoOyM3bObzhdfiqpne0AmSK_UakteTZxnjqJVrNV9A@mail.gmail.com>
2020-09-08 8:14 ` [PATCH v2 05/10] pwm: ntxec: Add driver " Lee Jones
2020-09-08 8:47 ` Andy Shevchenko
2020-09-08 9:35 ` Lee Jones
2020-09-10 19:13 ` Jonathan Neuschäfer
2020-09-10 19:09 ` Jonathan Neuschäfer
2020-09-05 13:32 ` [PATCH v2 06/10] dt-bindings: rtc: Add bindings for Netronix embedded controller RTC Jonathan Neuschäfer
2020-09-05 13:32 ` [PATCH v2 07/10] rtc: Introduce RTC_TIMESTAMP_END_2255 Jonathan Neuschäfer
2020-09-08 9:39 ` Alexandre Belloni
2020-09-10 19:21 ` Jonathan Neuschäfer
2020-09-05 14:45 ` [PATCH v2 08/10] rtc: New driver for RTC in Netronix embedded controller Jonathan Neuschäfer
[not found] ` <CAHp75Vca+Tp0v_Q4RBuUNSo_5aq_u6mBGeXecHULC1Avgm5=Xg@mail.gmail.com>
2020-09-10 19:42 ` Jonathan Neuschäfer
2020-09-05 14:45 ` [PATCH v2 09/10] MAINTAINERS: Add entry for " Jonathan Neuschäfer
2020-09-05 14:45 ` [PATCH v2 10/10] ARM: dts: imx50-kobo-aura: Add " Jonathan Neuschäfer
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