pwm: add support for Intel Low Power Subsystem PWM

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

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Chew, Kean Ho <kean.ho.chew@intel.com>
Signed-off-by: Chang, Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
Signed-off-by: Chew, Chiau Ee <chiau.ee.chew@intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 183 insertions, 0 deletions

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
new file mode 100644
index 000000000000..449e372050a0
--- /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@linux.intel.com>
+ * Author: Chew Kean Ho <kean.ho.chew@intel.com>
+ * Author: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
+ * Author: Chew Chiau Ee <chiau.ee.chew@intel.com>
+ *
+ * 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@linux.intel.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:pwm-lpss");