pwm: Add SPEAr PWM chip driver support

Add support for PWM chips present on SPEAr platforms. These PWM
chips support 4 channel output with programmable duty cycle and
frequency.

More details on these PWM chips can be obtained from relevant
chapter of reference manual, present at following[1] location.

1. http://www.st.com/internet/mcu/product/251211.jsp

Cc: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Shiraz Hashim <shiraz.hashim@st.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Vipin Kumar <vipin.kumar@st.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

1 files changed, 276 insertions, 0 deletions

diff --git a/drivers/pwm/pwm-spear.c b/drivers/pwm/pwm-spear.c
new file mode 100644
index 000000000000..6a8fd9b5dc42
--- /dev/null
+++ b/drivers/pwm/pwm-spear.c
@@ -0,0 +1,276 @@
+/*
+ * ST Microelectronics SPEAr Pulse Width Modulator driver
+ *
+ * Copyright (C) 2012 ST Microelectronics
+ * Shiraz Hashim <shiraz.hashim@st.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#define NUM_PWM         4
+
+/* PWM registers and bits definitions */
+#define PWMCR                   0x00    /* Control Register */
+#define PWMCR_PWM_ENABLE        0x1
+#define PWMCR_PRESCALE_SHIFT    2
+#define PWMCR_MIN_PRESCALE      0x00
+#define PWMCR_MAX_PRESCALE      0x3FFF
+
+#define PWMDCR                  0x04    /* Duty Cycle Register */
+#define PWMDCR_MIN_DUTY         0x0001
+#define PWMDCR_MAX_DUTY         0xFFFF
+
+#define PWMPCR                  0x08    /* Period Register */
+#define PWMPCR_MIN_PERIOD       0x0001
+#define PWMPCR_MAX_PERIOD       0xFFFF
+
+/* Following only available on 13xx SoCs */
+#define PWMMCR                  0x3C    /* Master Control Register */
+#define PWMMCR_PWM_ENABLE       0x1
+
+/**
+ * struct spear_pwm_chip - struct representing pwm chip
+ *
+ * @mmio_base: base address of pwm chip
+ * @clk: pointer to clk structure of pwm chip
+ * @chip: linux pwm chip representation
+ * @dev: pointer to device structure of pwm chip
+ */
+struct spear_pwm_chip {
+        void __iomem *mmio_base;
+        struct clk *clk;
+        struct pwm_chip chip;
+        struct device *dev;
+};
+
+static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip)
+{
+        return container_of(chip, struct spear_pwm_chip, chip);
+}
+
+static inline u32 spear_pwm_readl(struct spear_pwm_chip *chip, unsigned int num,
+                                  unsigned long offset)
+{
+        return readl_relaxed(chip->mmio_base + (num << 4) + offset);
+}
+
+static inline void spear_pwm_writel(struct spear_pwm_chip *chip,
+                                    unsigned int num, unsigned long offset,
+                                    unsigned long val)
+{
+        writel_relaxed(val, chip->mmio_base + (num << 4) + offset);
+}
+
+int spear_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, int duty_ns,
+                     int period_ns)
+{
+        struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
+        u64 val, div, clk_rate;
+        unsigned long prescale = PWMCR_MIN_PRESCALE, pv, dc;
+        int ret;
+
+        /*
+         * Find pv, dc and prescale to suit duty_ns and period_ns. This is done
+         * according to formulas described below:
+         *
+         * period_ns = 10^9 * (PRESCALE + 1) * PV / PWM_CLK_RATE
+         * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
+         *
+         * PV = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
+         * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
+         */
+        clk_rate = clk_get_rate(pc->clk);
+        while (1) {
+                div = 1000000000;
+                div *= 1 + prescale;
+                val = clk_rate * period_ns;
+                pv = div64_u64(val, div);
+                val = clk_rate * duty_ns;
+                dc = div64_u64(val, div);
+
+                /* if duty_ns and period_ns are not achievable then return */
+                if (pv < PWMPCR_MIN_PERIOD || dc < PWMDCR_MIN_DUTY)
+                        return -EINVAL;
+
+                /*
+                 * if pv and dc have crossed their upper limit, then increase
+                 * prescale and recalculate pv and dc.
+                 */
+                if (pv > PWMPCR_MAX_PERIOD || dc > PWMDCR_MAX_DUTY) {
+                        if (++prescale > PWMCR_MAX_PRESCALE)
+                                return -EINVAL;
+                        continue;
+                }
+                break;
+        }
+
+        /*
+         * NOTE: the clock to PWM has to be enabled first before writing to the
+         * registers.
+         */
+        ret = clk_enable(pc->clk);
+        if (ret)
+                return ret;
+
+        spear_pwm_writel(pc, pwm->hwpwm, PWMCR,
+                        prescale << PWMCR_PRESCALE_SHIFT);
+        spear_pwm_writel(pc, pwm->hwpwm, PWMDCR, dc);
+        spear_pwm_writel(pc, pwm->hwpwm, PWMPCR, pv);
+        clk_disable(pc->clk);
+
+        return 0;
+}
+
+static int spear_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+        struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
+        int rc = 0;
+        u32 val;
+
+        rc = clk_enable(pc->clk);
+        if (!rc)
+                return rc;
+
+        val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
+        val |= PWMCR_PWM_ENABLE;
+        spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
+
+        return 0;
+}
+
+static void spear_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+        struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
+        u32 val;
+
+        val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
+        val &= ~PWMCR_PWM_ENABLE;
+        spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
+
+        clk_disable(pc->clk);
+}
+
+static const struct pwm_ops spear_pwm_ops = {
+        .config = spear_pwm_config,
+        .enable = spear_pwm_enable,
+        .disable = spear_pwm_disable,
+        .owner = THIS_MODULE,
+};
+
+static int spear_pwm_probe(struct platform_device *pdev)
+{
+        struct device_node *np = pdev->dev.of_node;
+        struct spear_pwm_chip *pc;
+        struct resource *r;
+        int ret;
+        u32 val;
+
+        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        if (!r) {
+                dev_err(&pdev->dev, "no memory resources defined\n");
+                return -ENODEV;
+        }
+
+        pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
+        if (!pc) {
+                dev_err(&pdev->dev, "failed to allocate memory\n");
+                return -ENOMEM;
+        }
+
+        pc->mmio_base = devm_request_and_ioremap(&pdev->dev, r);
+        if (!pc->mmio_base)
+                return -EADDRNOTAVAIL;
+
+        pc->clk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(pc->clk))
+                return PTR_ERR(pc->clk);
+
+        pc->dev = &pdev->dev;
+        platform_set_drvdata(pdev, pc);
+
+        pc->chip.dev = &pdev->dev;
+        pc->chip.ops = &spear_pwm_ops;
+        pc->chip.base = -1;
+        pc->chip.npwm = NUM_PWM;
+
+        ret = clk_prepare(pc->clk);
+        if (!ret)
+                return ret;
+
+        if (of_device_is_compatible(np, "st,spear1340-pwm")) {
+                ret = clk_enable(pc->clk);
+                if (!ret) {
+                        clk_unprepare(pc->clk);
+                        return ret;
+                }
+                /*
+                 * Following enables PWM chip, channels would still be
+                 * enabled individually through their control register
+                 */
+                val = readl_relaxed(pc->mmio_base + PWMMCR);
+                val |= PWMMCR_PWM_ENABLE;
+                writel_relaxed(val, pc->mmio_base + PWMMCR);
+
+                clk_disable(pc->clk);
+        }
+
+        ret = pwmchip_add(&pc->chip);
+        if (!ret) {
+                clk_unprepare(pc->clk);
+                dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
+        }
+
+        return ret;
+}
+
+static int spear_pwm_remove(struct platform_device *pdev)
+{
+        struct spear_pwm_chip *pc = platform_get_drvdata(pdev);
+        int i;
+
+        for (i = 0; i < NUM_PWM; i++)
+                pwm_disable(&pc->chip.pwms[i]);
+
+        /* clk was prepared in probe, hence unprepare it here */
+        clk_unprepare(pc->clk);
+        return pwmchip_remove(&pc->chip);
+}
+
+static struct of_device_id spear_pwm_of_match[] = {
+        { .compatible = "st,spear320-pwm" },
+        { .compatible = "st,spear1340-pwm" },
+        { }
+};
+
+MODULE_DEVICE_TABLE(of, spear_pwm_of_match);
+
+static struct platform_driver spear_pwm_driver = {
+        .driver = {
+                .name = "spear-pwm",
+                .of_match_table = spear_pwm_of_match,
+        },
+        .probe = spear_pwm_probe,
+        .remove = spear_pwm_remove,
+};
+
+module_platform_driver(spear_pwm_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Shiraz Hashim <shiraz.hashim@st.com>");
+MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
+MODULE_ALIAS("platform:spear-pwm");