[PATCH v3] pwm: add support for Intel Low Power Subsystem PWM

[Chew Chiau Ee]

From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>

Add support for Intel Low Power I/O subsystem PWM controllers found on
Intel BayTrail SoC.

Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Chew, Kean Ho <kean.ho.chew@xxxxxxxxx>
Signed-off-by: Chang, Rebecca Swee Fun <rebecca.swee.fun.chang@xxxxxxxxx>
Signed-off-by: Chew, Chiau Ee <chiau.ee.chew@xxxxxxxxx>
---
 changelog v3:
 * check validity of clk_get_rate()'s return value before division
 * update MODULE_LICENSE()line

 drivers/pwm/Kconfig    |   10 +++
 drivers/pwm/Makefile   |    1 +
 drivers/pwm/pwm-lpss.c |  183 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 194 insertions(+), 0 deletions(-)
 create mode 100644 drivers/pwm/pwm-lpss.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 1445ba1..5b34ff2 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -138,6 +138,16 @@ config PWM_LPC32XX
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-lpc32xx.
 
+config PWM_LPSS
+	tristate "Intel LPSS PWM support"
+	depends on ACPI
+	help
+	  Generic PWM framework driver for Intel Low Power Subsystem PWM
+	  controller.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-lpss.
+
 config PWM_MXS
 	tristate "Freescale MXS PWM support"
 	depends on ARCH_MXS && OF
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 82f294e..e57d2c3 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o
 obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
 obj-$(CONFIG_PWM_LP3943)	+= pwm-lp3943.o
 obj-$(CONFIG_PWM_LPC32XX)	+= pwm-lpc32xx.o
+obj-$(CONFIG_PWM_LPSS)		+= pwm-lpss.o
 obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
 obj-$(CONFIG_PWM_PCA9685)	+= pwm-pca9685.o
 obj-$(CONFIG_PWM_PUV3)		+= pwm-puv3.o
diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
new file mode 100644
index 0000000..449e372
--- /dev/null
+++ b/drivers/pwm/pwm-lpss.c
@@ -0,0 +1,183 @@
+/*
+ * Intel Low Power Subsystem PWM controller driver
+ *
+ * Copyright (C) 2014, Intel Corporation
+ * Author: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
+ * Author: Chew Kean Ho <kean.ho.chew@xxxxxxxxx>
+ * Author: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@xxxxxxxxx>
+ * Author: Chew Chiau Ee <chiau.ee.chew@xxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/acpi.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pwm.h>
+#include <linux/platform_device.h>
+
+#define PWM				0x00000000
+#define PWM_ENABLE			BIT(31)
+#define PWM_SW_UPDATE			BIT(30)
+#define PWM_BASE_UNIT_SHIFT		8
+#define PWM_BASE_UNIT_MASK		0x00ffff00
+#define PWM_ON_TIME_DIV_MASK		0x000000ff
+#define PWM_DIVISION_CORRECTION		0x2
+#define PWM_LIMIT			(0x8000 + PWM_DIVISION_CORRECTION)
+#define NSECS_PER_SEC			1000000000UL
+
+struct pwm_lpss_chip {
+	struct pwm_chip chip;
+	void __iomem *regs;
+	struct clk *clk;
+};
+
+static inline struct pwm_lpss_chip *to_lpwm(struct pwm_chip *chip)
+{
+	return container_of(chip, struct pwm_lpss_chip, chip);
+}
+
+static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			   int duty_ns, int period_ns)
+{
+	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
+	u8 on_time_div;
+	unsigned long c;
+	unsigned long long base_unit, freq = NSECS_PER_SEC;
+	u32 ctrl;
+
+	do_div(freq, period_ns);
+
+	/* The equation is: base_unit = ((freq / c) * 65536) + correction */
+	base_unit = freq * 65536;
+
+	c = clk_get_rate(lpwm->clk);
+	if (!c)
+		return -EINVAL;
+
+	do_div(base_unit, c);
+	base_unit += PWM_DIVISION_CORRECTION;
+	if (base_unit > PWM_LIMIT)
+		return -EINVAL;
+
+	if (duty_ns <= 0)
+		duty_ns = 1;
+	on_time_div = 255 - (255 * duty_ns / period_ns);
+
+	ctrl = readl(lpwm->regs + PWM);
+	ctrl &= ~(PWM_BASE_UNIT_MASK | PWM_ON_TIME_DIV_MASK);
+	ctrl |= (u16) base_unit << PWM_BASE_UNIT_SHIFT;
+	ctrl |= on_time_div;
+	/* request PWM to update on next cycle */
+	ctrl |= PWM_SW_UPDATE;
+	writel(ctrl, lpwm->regs + PWM);
+
+	return 0;
+}
+
+static int pwm_lpss_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
+	u32 ctrl;
+	int ret;
+
+	ret = clk_prepare_enable(lpwm->clk);
+	if (ret)
+		return ret;
+
+	ctrl = readl(lpwm->regs + PWM);
+	writel(ctrl | PWM_ENABLE, lpwm->regs + PWM);
+
+	return 0;
+}
+
+static void pwm_lpss_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
+	u32 ctrl;
+
+	ctrl = readl(lpwm->regs + PWM);
+	writel(ctrl & ~PWM_ENABLE, lpwm->regs + PWM);
+
+	clk_disable_unprepare(lpwm->clk);
+}
+
+static const struct pwm_ops pwm_lpss_ops = {
+	.config = pwm_lpss_config,
+	.enable = pwm_lpss_enable,
+	.disable = pwm_lpss_disable,
+	.owner = THIS_MODULE,
+};
+
+static const struct acpi_device_id pwm_lpss_acpi_match[] = {
+	{ "80860F09", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, pwm_lpss_acpi_match);
+
+static int pwm_lpss_probe(struct platform_device *pdev)
+{
+	struct pwm_lpss_chip *lpwm;
+	struct resource *r;
+	int ret;
+
+	lpwm = devm_kzalloc(&pdev->dev, sizeof(*lpwm), GFP_KERNEL);
+	if (!lpwm)
+		return -ENOMEM;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+	lpwm->regs = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(lpwm->regs))
+		return PTR_ERR(lpwm->regs);
+
+	lpwm->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(lpwm->clk)) {
+		dev_err(&pdev->dev, "failed to get PWM clock\n");
+		return PTR_ERR(lpwm->clk);
+	}
+
+	lpwm->chip.dev = &pdev->dev;
+	lpwm->chip.ops = &pwm_lpss_ops;
+	lpwm->chip.base = -1;
+	lpwm->chip.npwm = 1;
+
+	ret = pwmchip_add(&lpwm->chip);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, lpwm);
+	return 0;
+}
+
+static int pwm_lpss_remove(struct platform_device *pdev)
+{
+	struct pwm_lpss_chip *lpwm = platform_get_drvdata(pdev);
+	u32 ctrl;
+
+	ctrl = readl(lpwm->regs + PWM);
+	writel(ctrl & ~PWM_ENABLE, lpwm->regs + PWM);
+
+	return pwmchip_remove(&lpwm->chip);
+}
+
+static struct platform_driver pwm_lpss_driver = {
+	.driver = {
+		.name = "pwm-lpss",
+		.acpi_match_table = pwm_lpss_acpi_match,
+	},
+	.probe = pwm_lpss_probe,
+	.remove = pwm_lpss_remove,
+};
+module_platform_driver(pwm_lpss_driver);
+
+MODULE_DESCRIPTION("PWM driver for Intel LPSS");
+MODULE_AUTHOR("Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:pwm-lpss");
-- 
1.7.4.4

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