pwm: kona: Introduce Kona PWM controller support

Add support for the six-channel Kona PWM controller found on Broadcom
mobile SoCs like bcm281xx.

Signed-off-by: Tim Kryger <tim.kryger@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

3 files changed, 328 insertions, 0 deletions

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 5b34ff29ea38..4ad7b89a4cb4 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -62,6 +62,15 @@ config PWM_ATMEL_TCB
           To compile this driver as a module, choose M here: the module
           will be called pwm-atmel-tcb.
 
+config PWM_BCM_KONA
+        tristate "Kona PWM support"
+        depends on ARCH_BCM_MOBILE
+        help
+          Generic PWM framework driver for Broadcom Kona PWM block.
+
+          To compile this driver as a module, choose M here: the module
+          will be called pwm-bcm-kona.
+
 config PWM_BFIN
         tristate "Blackfin PWM support"
         depends on BFIN_GPTIMERS
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index e57d2c38a794..5c86a19d5d39 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)        += pwm-ab8500.o
 obj-$(CONFIG_PWM_ATMEL)         += pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_TCB)     += pwm-atmel-tcb.o
+obj-$(CONFIG_PWM_BCM_KONA)      += pwm-bcm-kona.o
 obj-$(CONFIG_PWM_BFIN)          += pwm-bfin.o
 obj-$(CONFIG_PWM_CLPS711X)      += pwm-clps711x.o
 obj-$(CONFIG_PWM_EP93XX)        += pwm-ep93xx.o
diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c
new file mode 100644
index 000000000000..02bc048892a9
--- /dev/null
+++ b/drivers/pwm/pwm-bcm-kona.c
@@ -0,0 +1,318 @@
+/*
+ * Copyright (C) 2014 Broadcom Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/ioport.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>
+
+/*
+ * The Kona PWM has some unusual characteristics.  Here are the main points.
+ *
+ * 1) There is no disable bit and the hardware docs advise programming a zero
+ *    duty to achieve output equivalent to that of a normal disable operation.
+ *
+ * 2) Changes to prescale, duty, period, and polarity do not take effect until
+ *    a subsequent rising edge of the trigger bit.
+ *
+ * 3) If the smooth bit and trigger bit are both low, the output is a constant
+ *    high signal.  Otherwise, the earlier waveform continues to be output.
+ *
+ * 4) If the smooth bit is set on the rising edge of the trigger bit, output
+ *    will transition to the new settings on a period boundary (which could be
+ *    seconds away).  If the smooth bit is clear, new settings will be applied
+ *    as soon as possible (the hardware always has a 400ns delay).
+ *
+ * 5) When the external clock that feeds the PWM is disabled, output is pegged
+ *    high or low depending on its state at that exact instant.
+ */
+
+#define PWM_CONTROL_OFFSET                      (0x00000000)
+#define PWM_CONTROL_SMOOTH_SHIFT(chan)          (24 + (chan))
+#define PWM_CONTROL_TYPE_SHIFT(chan)            (16 + (chan))
+#define PWM_CONTROL_POLARITY_SHIFT(chan)        (8 + (chan))
+#define PWM_CONTROL_TRIGGER_SHIFT(chan)         (chan)
+
+#define PRESCALE_OFFSET                         (0x00000004)
+#define PRESCALE_SHIFT(chan)                    ((chan) << 2)
+#define PRESCALE_MASK(chan)                     (0x7 << PRESCALE_SHIFT(chan))
+#define PRESCALE_MIN                            (0x00000000)
+#define PRESCALE_MAX                            (0x00000007)
+
+#define PERIOD_COUNT_OFFSET(chan)               (0x00000008 + ((chan) << 3))
+#define PERIOD_COUNT_MIN                        (0x00000002)
+#define PERIOD_COUNT_MAX                        (0x00ffffff)
+
+#define DUTY_CYCLE_HIGH_OFFSET(chan)            (0x0000000c + ((chan) << 3))
+#define DUTY_CYCLE_HIGH_MIN                     (0x00000000)
+#define DUTY_CYCLE_HIGH_MAX                     (0x00ffffff)
+
+struct kona_pwmc {
+        struct pwm_chip chip;
+        void __iomem *base;
+        struct clk *clk;
+};
+
+static inline struct kona_pwmc *to_kona_pwmc(struct pwm_chip *_chip)
+{
+        return container_of(_chip, struct kona_pwmc, chip);
+}
+
+static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
+{
+        unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
+
+        /* Clear trigger bit but set smooth bit to maintain old output */
+        value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
+        value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
+        writel(value, kp->base + PWM_CONTROL_OFFSET);
+
+        /* Set trigger bit and clear smooth bit to apply new settings */
+        value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
+        value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
+        writel(value, kp->base + PWM_CONTROL_OFFSET);
+}
+
+static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
+                            int duty_ns, int period_ns)
+{
+        struct kona_pwmc *kp = to_kona_pwmc(chip);
+        u64 val, div, rate;
+        unsigned long prescale = PRESCALE_MIN, pc, dc;
+        unsigned int value, chan = pwm->hwpwm;
+
+        /*
+         * Find period count, duty count and prescale to suit duty_ns and
+         * period_ns. This is done according to formulas described below:
+         *
+         * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
+         * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
+         *
+         * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
+         * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
+         */
+
+        rate = clk_get_rate(kp->clk);
+
+        while (1) {
+                div = 1000000000;
+                div *= 1 + prescale;
+                val = rate * period_ns;
+                pc = div64_u64(val, div);
+                val = rate * duty_ns;
+                dc = div64_u64(val, div);
+
+                /* If duty_ns or period_ns are not achievable then return */
+                if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN)
+                        return -EINVAL;
+
+                /* If pc and dc are in bounds, the calculation is done */
+                if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
+                        break;
+
+                /* Otherwise, increase prescale and recalculate pc and dc */
+                if (++prescale > PRESCALE_MAX)
+                        return -EINVAL;
+        }
+
+        /* If the PWM channel is enabled, write the settings to the HW */
+        if (test_bit(PWMF_ENABLED, &pwm->flags)) {
+                value = readl(kp->base + PRESCALE_OFFSET);
+                value &= ~PRESCALE_MASK(chan);
+                value |= prescale << PRESCALE_SHIFT(chan);
+                writel(value, kp->base + PRESCALE_OFFSET);
+
+                writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan));
+
+                writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
+
+                kona_pwmc_apply_settings(kp, chan);
+        }
+
+        return 0;
+}
+
+static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+                                  enum pwm_polarity polarity)
+{
+        struct kona_pwmc *kp = to_kona_pwmc(chip);
+        unsigned int chan = pwm->hwpwm;
+        unsigned int value;
+        int ret;
+
+        ret = clk_prepare_enable(kp->clk);
+        if (ret < 0) {
+                dev_err(chip->dev, "failed to enable clock: %d\n", ret);
+                return ret;
+        }
+
+        value = readl(kp->base + PWM_CONTROL_OFFSET);
+
+        if (polarity == PWM_POLARITY_NORMAL)
+                value |= 1 << PWM_CONTROL_POLARITY_SHIFT(chan);
+        else
+                value &= ~(1 << PWM_CONTROL_POLARITY_SHIFT(chan));
+
+        writel(value, kp->base + PWM_CONTROL_OFFSET);
+
+        kona_pwmc_apply_settings(kp, chan);
+
+        /* Wait for waveform to settle before gating off the clock */
+        ndelay(400);
+
+        clk_disable_unprepare(kp->clk);
+
+        return 0;
+}
+
+static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+        struct kona_pwmc *kp = to_kona_pwmc(chip);
+        int ret;
+
+        ret = clk_prepare_enable(kp->clk);
+        if (ret < 0) {
+                dev_err(chip->dev, "failed to enable clock: %d\n", ret);
+                return ret;
+        }
+
+        ret = kona_pwmc_config(chip, pwm, pwm->duty_cycle, pwm->period);
+        if (ret < 0) {
+                clk_disable_unprepare(kp->clk);
+                return ret;
+        }
+
+        return 0;
+}
+
+static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+        struct kona_pwmc *kp = to_kona_pwmc(chip);
+        unsigned int chan = pwm->hwpwm;
+
+        /* Simulate a disable by configuring for zero duty */
+        writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
+        kona_pwmc_apply_settings(kp, chan);
+
+        /* Wait for waveform to settle before gating off the clock */
+        ndelay(400);
+
+        clk_disable_unprepare(kp->clk);
+}
+
+static const struct pwm_ops kona_pwm_ops = {
+        .config = kona_pwmc_config,
+        .set_polarity = kona_pwmc_set_polarity,
+        .enable = kona_pwmc_enable,
+        .disable = kona_pwmc_disable,
+        .owner = THIS_MODULE,
+};
+
+static int kona_pwmc_probe(struct platform_device *pdev)
+{
+        struct kona_pwmc *kp;
+        struct resource *res;
+        unsigned int chan;
+        unsigned int value = 0;
+        int ret = 0;
+
+        kp = devm_kzalloc(&pdev->dev, sizeof(*kp), GFP_KERNEL);
+        if (kp == NULL)
+                return -ENOMEM;
+
+        platform_set_drvdata(pdev, kp);
+
+        kp->chip.dev = &pdev->dev;
+        kp->chip.ops = &kona_pwm_ops;
+        kp->chip.base = -1;
+        kp->chip.npwm = 6;
+        kp->chip.of_xlate = of_pwm_xlate_with_flags;
+        kp->chip.of_pwm_n_cells = 3;
+        kp->chip.can_sleep = true;
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        kp->base = devm_ioremap_resource(&pdev->dev, res);
+        if (IS_ERR(kp->base))
+                return PTR_ERR(kp->base);
+
+        kp->clk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(kp->clk)) {
+                dev_err(&pdev->dev, "failed to get clock: %ld\n",
+                        PTR_ERR(kp->clk));
+                return PTR_ERR(kp->clk);
+        }
+
+        ret = clk_prepare_enable(kp->clk);
+        if (ret < 0) {
+                dev_err(&pdev->dev, "failed to enable clock: %d\n", ret);
+                return ret;
+        }
+
+        /* Set smooth mode, push/pull, and normal polarity for all channels */
+        for (chan = 0; chan < kp->chip.npwm; chan++) {
+                value |= (1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
+                value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan));
+                value |= (1 << PWM_CONTROL_POLARITY_SHIFT(chan));
+        }
+
+        writel(value, kp->base + PWM_CONTROL_OFFSET);
+
+        clk_disable_unprepare(kp->clk);
+
+        ret = pwmchip_add(&kp->chip);
+        if (ret < 0)
+                dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
+
+        return ret;
+}
+
+static int kona_pwmc_remove(struct platform_device *pdev)
+{
+        struct kona_pwmc *kp = platform_get_drvdata(pdev);
+        unsigned int chan;
+
+        for (chan = 0; chan < kp->chip.npwm; chan++)
+                if (test_bit(PWMF_ENABLED, &kp->chip.pwms[chan].flags))
+                        clk_disable_unprepare(kp->clk);
+
+        return pwmchip_remove(&kp->chip);
+}
+
+static const struct of_device_id bcm_kona_pwmc_dt[] = {
+        { .compatible = "brcm,kona-pwm" },
+        { },
+};
+MODULE_DEVICE_TABLE(of, bcm_kona_pwmc_dt);
+
+static struct platform_driver kona_pwmc_driver = {
+        .driver = {
+                .name = "bcm-kona-pwm",
+                .of_match_table = bcm_kona_pwmc_dt,
+        },
+        .probe = kona_pwmc_probe,
+        .remove = kona_pwmc_remove,
+};
+module_platform_driver(kona_pwmc_driver);
+
+MODULE_AUTHOR("Broadcom Corporation <bcm-kernel-feedback-list@broadcom.com>");
+MODULE_AUTHOR("Tim Kryger <tkryger@broadcom.com>");
+MODULE_DESCRIPTION("Broadcom Kona PWM driver");
+MODULE_LICENSE("GPL v2");