pwm: atmel: add Timer Counter Block PWM driver

This patch adds a PWM driver based on Atmel Timer Counter Block. The
Timer Counter Block is used in Waveform generator mode.

A Timer Counter Block provides up to 6 PWM devices grouped by 2:
* group 0 = PWM 0 and 1
* group 1 = PWM 2 and 3
* group 2 = PMW 4 and 5

PWM devices in a given group must be configured with the same period
value. If a PWM device in a group tries to change the period value and
the other device is already configured with a different value an error
will be returned.

This driver requires device tree support. The Timer Counter Block number
used to create a PWM chip is given by the tc-block field in an
"atmel,tcb-pwm" compatible node.

This patch was tested on kizbox board (at91sam9g20 SoC) with pwm-leds.

Signed-off-by: Boris BREZILLON <linux-arm@overkiz.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

3 files changed, 458 insertions, 0 deletions

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index e513cd998170..10b6afc94bc3 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -37,6 +37,18 @@ config PWM_AB8500
           To compile this driver as a module, choose M here: the module
           will be called pwm-ab8500.
 
+config PWM_ATMEL_TCB
+        tristate "TC Block PWM"
+        depends on ATMEL_TCLIB && OF
+        help
+          Generic PWM framework driver for Atmel Timer Counter Block.
+
+          A Timer Counter Block provides 6 PWM devices grouped by 2.
+          Devices in a given group must have the same period.
+
+          To compile this driver as a module, choose M here: the module
+          will be called pwm-atmel-tcb.
+
 config PWM_BFIN
         tristate "Blackfin PWM support"
         depends on BFIN_GPTIMERS
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 62a2963cfe58..94ba21e24bd6 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -1,5 +1,6 @@
 obj-$(CONFIG_PWM)               += core.o
 obj-$(CONFIG_PWM_AB8500)        += pwm-ab8500.o
+obj-$(CONFIG_PWM_ATMEL_TCB)     += pwm-atmel-tcb.o
 obj-$(CONFIG_PWM_BFIN)          += pwm-bfin.o
 obj-$(CONFIG_PWM_IMX)           += pwm-imx.o
 obj-$(CONFIG_PWM_JZ4740)        += pwm-jz4740.o
diff --git a/drivers/pwm/pwm-atmel-tcb.c b/drivers/pwm/pwm-atmel-tcb.c
new file mode 100644
index 000000000000..16cb53092857
--- /dev/null
+++ b/drivers/pwm/pwm-atmel-tcb.c
@@ -0,0 +1,445 @@
+/*
+ * Copyright (C) Overkiz SAS 2012
+ *
+ * Author: Boris BREZILLON <b.brezillon@overkiz.com>
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/ioport.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/atmel_tc.h>
+#include <linux/pwm.h>
+#include <linux/of_device.h>
+#include <linux/slab.h>
+
+#define NPWM    6
+
+#define ATMEL_TC_ACMR_MASK      (ATMEL_TC_ACPA | ATMEL_TC_ACPC |        \
+                                 ATMEL_TC_AEEVT | ATMEL_TC_ASWTRG)
+
+#define ATMEL_TC_BCMR_MASK      (ATMEL_TC_BCPB | ATMEL_TC_BCPC |        \
+                                 ATMEL_TC_BEEVT | ATMEL_TC_BSWTRG)
+
+struct atmel_tcb_pwm_device {
+        enum pwm_polarity polarity;     /* PWM polarity */
+        unsigned div;                   /* PWM clock divider */
+        unsigned duty;                  /* PWM duty expressed in clk cycles */
+        unsigned period;                /* PWM period expressed in clk cycles */
+};
+
+struct atmel_tcb_pwm_chip {
+        struct pwm_chip chip;
+        spinlock_t lock;
+        struct atmel_tc *tc;
+        struct atmel_tcb_pwm_device *pwms[NPWM];
+};
+
+static inline struct atmel_tcb_pwm_chip *to_tcb_chip(struct pwm_chip *chip)
+{
+        return container_of(chip, struct atmel_tcb_pwm_chip, chip);
+}
+
+static int atmel_tcb_pwm_set_polarity(struct pwm_chip *chip,
+                                      struct pwm_device *pwm,
+                                      enum pwm_polarity polarity)
+{
+        struct atmel_tcb_pwm_device *tcbpwm = pwm_get_chip_data(pwm);
+
+        tcbpwm->polarity = polarity;
+
+        return 0;
+}
+
+static int atmel_tcb_pwm_request(struct pwm_chip *chip,
+                                 struct pwm_device *pwm)
+{
+        struct atmel_tcb_pwm_chip *tcbpwmc = to_tcb_chip(chip);
+        struct atmel_tcb_pwm_device *tcbpwm;
+        struct atmel_tc *tc = tcbpwmc->tc;
+        void __iomem *regs = tc->regs;
+        unsigned group = pwm->hwpwm / 2;
+        unsigned index = pwm->hwpwm % 2;
+        unsigned cmr;
+        int ret;
+
+        tcbpwm = devm_kzalloc(chip->dev, sizeof(*tcbpwm), GFP_KERNEL);
+        if (!tcbpwm)
+                return -ENOMEM;
+
+        ret = clk_enable(tc->clk[group]);
+        if (ret) {
+                devm_kfree(chip->dev, tcbpwm);
+                return ret;
+        }
+
+        pwm_set_chip_data(pwm, tcbpwm);
+        tcbpwm->polarity = PWM_POLARITY_NORMAL;
+        tcbpwm->duty = 0;
+        tcbpwm->period = 0;
+        tcbpwm->div = 0;
+
+        spin_lock(&tcbpwmc->lock);
+        cmr = __raw_readl(regs + ATMEL_TC_REG(group, CMR));
+        /*
+         * Get init config from Timer Counter registers if
+         * Timer Counter is already configured as a PWM generator.
+         */
+        if (cmr & ATMEL_TC_WAVE) {
+                if (index == 0)
+                        tcbpwm->duty =
+                                __raw_readl(regs + ATMEL_TC_REG(group, RA));
+                else
+                        tcbpwm->duty =
+                                __raw_readl(regs + ATMEL_TC_REG(group, RB));
+
+                tcbpwm->div = cmr & ATMEL_TC_TCCLKS;
+                tcbpwm->period = __raw_readl(regs + ATMEL_TC_REG(group, RC));
+                cmr &= (ATMEL_TC_TCCLKS | ATMEL_TC_ACMR_MASK |
+                        ATMEL_TC_BCMR_MASK);
+        } else
+                cmr = 0;
+
+        cmr |= ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO | ATMEL_TC_EEVT_XC0;
+        __raw_writel(cmr, regs + ATMEL_TC_REG(group, CMR));
+        spin_unlock(&tcbpwmc->lock);
+
+        tcbpwmc->pwms[pwm->hwpwm] = tcbpwm;
+
+        return 0;
+}
+
+static void atmel_tcb_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+        struct atmel_tcb_pwm_chip *tcbpwmc = to_tcb_chip(chip);
+        struct atmel_tcb_pwm_device *tcbpwm = pwm_get_chip_data(pwm);
+        struct atmel_tc *tc = tcbpwmc->tc;
+
+        clk_disable(tc->clk[pwm->hwpwm / 2]);
+        tcbpwmc->pwms[pwm->hwpwm] = NULL;
+        devm_kfree(chip->dev, tcbpwm);
+}
+
+static void atmel_tcb_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+        struct atmel_tcb_pwm_chip *tcbpwmc = to_tcb_chip(chip);
+        struct atmel_tcb_pwm_device *tcbpwm = pwm_get_chip_data(pwm);
+        struct atmel_tc *tc = tcbpwmc->tc;
+        void __iomem *regs = tc->regs;
+        unsigned group = pwm->hwpwm / 2;
+        unsigned index = pwm->hwpwm % 2;
+        unsigned cmr;
+        enum pwm_polarity polarity = tcbpwm->polarity;
+
+        /*
+         * If duty is 0 the timer will be stopped and we have to
+         * configure the output correctly on software trigger:
+         *  - set output to high if PWM_POLARITY_INVERSED
+         *  - set output to low if PWM_POLARITY_NORMAL
+         *
+         * This is why we're reverting polarity in this case.
+         */
+        if (tcbpwm->duty == 0)
+                polarity = !polarity;
+
+        spin_lock(&tcbpwmc->lock);
+        cmr = __raw_readl(regs + ATMEL_TC_REG(group, CMR));
+
+        /* flush old setting and set the new one */
+        if (index == 0) {
+                cmr &= ~ATMEL_TC_ACMR_MASK;
+                if (polarity == PWM_POLARITY_INVERSED)
+                        cmr |= ATMEL_TC_ASWTRG_CLEAR;
+                else
+                        cmr |= ATMEL_TC_ASWTRG_SET;
+        } else {
+                cmr &= ~ATMEL_TC_BCMR_MASK;
+                if (polarity == PWM_POLARITY_INVERSED)
+                        cmr |= ATMEL_TC_BSWTRG_CLEAR;
+                else
+                        cmr |= ATMEL_TC_BSWTRG_SET;
+        }
+
+        __raw_writel(cmr, regs + ATMEL_TC_REG(group, CMR));
+
+        /*
+         * Use software trigger to apply the new setting.
+         * If both PWM devices in this group are disabled we stop the clock.
+         */
+        if (!(cmr & (ATMEL_TC_ACPC | ATMEL_TC_BCPC)))
+                __raw_writel(ATMEL_TC_SWTRG | ATMEL_TC_CLKDIS,
+                             regs + ATMEL_TC_REG(group, CCR));
+        else
+                __raw_writel(ATMEL_TC_SWTRG, regs +
+                             ATMEL_TC_REG(group, CCR));
+
+        spin_unlock(&tcbpwmc->lock);
+}
+
+static int atmel_tcb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+        struct atmel_tcb_pwm_chip *tcbpwmc = to_tcb_chip(chip);
+        struct atmel_tcb_pwm_device *tcbpwm = pwm_get_chip_data(pwm);
+        struct atmel_tc *tc = tcbpwmc->tc;
+        void __iomem *regs = tc->regs;
+        unsigned group = pwm->hwpwm / 2;
+        unsigned index = pwm->hwpwm % 2;
+        u32 cmr;
+        enum pwm_polarity polarity = tcbpwm->polarity;
+
+        /*
+         * If duty is 0 the timer will be stopped and we have to
+         * configure the output correctly on software trigger:
+         *  - set output to high if PWM_POLARITY_INVERSED
+         *  - set output to low if PWM_POLARITY_NORMAL
+         *
+         * This is why we're reverting polarity in this case.
+         */
+        if (tcbpwm->duty == 0)
+                polarity = !polarity;
+
+        spin_lock(&tcbpwmc->lock);
+        cmr = __raw_readl(regs + ATMEL_TC_REG(group, CMR));
+
+        /* flush old setting and set the new one */
+        cmr &= ~ATMEL_TC_TCCLKS;
+
+        if (index == 0) {
+                cmr &= ~ATMEL_TC_ACMR_MASK;
+
+                /* Set CMR flags according to given polarity */
+                if (polarity == PWM_POLARITY_INVERSED)
+                        cmr |= ATMEL_TC_ASWTRG_CLEAR;
+                else
+                        cmr |= ATMEL_TC_ASWTRG_SET;
+        } else {
+                cmr &= ~ATMEL_TC_BCMR_MASK;
+                if (polarity == PWM_POLARITY_INVERSED)
+                        cmr |= ATMEL_TC_BSWTRG_CLEAR;
+                else
+                        cmr |= ATMEL_TC_BSWTRG_SET;
+        }
+
+        /*
+         * If duty is 0 or equal to period there's no need to register
+         * a specific action on RA/RB and RC compare.
+         * The output will be configured on software trigger and keep
+         * this config till next config call.
+         */
+        if (tcbpwm->duty != tcbpwm->period && tcbpwm->duty > 0) {
+                if (index == 0) {
+                        if (polarity == PWM_POLARITY_INVERSED)
+                                cmr |= ATMEL_TC_ACPA_SET | ATMEL_TC_ACPC_CLEAR;
+                        else
+                                cmr |= ATMEL_TC_ACPA_CLEAR | ATMEL_TC_ACPC_SET;
+                } else {
+                        if (polarity == PWM_POLARITY_INVERSED)
+                                cmr |= ATMEL_TC_BCPB_SET | ATMEL_TC_BCPC_CLEAR;
+                        else
+                                cmr |= ATMEL_TC_BCPB_CLEAR | ATMEL_TC_BCPC_SET;
+                }
+        }
+
+        __raw_writel(cmr, regs + ATMEL_TC_REG(group, CMR));
+
+        if (index == 0)
+                __raw_writel(tcbpwm->duty, regs + ATMEL_TC_REG(group, RA));
+        else
+                __raw_writel(tcbpwm->duty, regs + ATMEL_TC_REG(group, RB));
+
+        __raw_writel(tcbpwm->period, regs + ATMEL_TC_REG(group, RC));
+
+        /* Use software trigger to apply the new setting */
+        __raw_writel(ATMEL_TC_CLKEN | ATMEL_TC_SWTRG,
+                     regs + ATMEL_TC_REG(group, CCR));
+        spin_unlock(&tcbpwmc->lock);
+        return 0;
+}
+
+static int atmel_tcb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+                                int duty_ns, int period_ns)
+{
+        struct atmel_tcb_pwm_chip *tcbpwmc = to_tcb_chip(chip);
+        struct atmel_tcb_pwm_device *tcbpwm = pwm_get_chip_data(pwm);
+        unsigned group = pwm->hwpwm / 2;
+        unsigned index = pwm->hwpwm % 2;
+        struct atmel_tcb_pwm_device *atcbpwm = NULL;
+        struct atmel_tc *tc = tcbpwmc->tc;
+        int i;
+        int slowclk = 0;
+        unsigned period;
+        unsigned duty;
+        unsigned rate = clk_get_rate(tc->clk[group]);
+        unsigned long long min;
+        unsigned long long max;
+
+        /*
+         * Find best clk divisor:
+         * the smallest divisor which can fulfill the period_ns requirements.
+         */
+        for (i = 0; i < 5; ++i) {
+                if (atmel_tc_divisors[i] == 0) {
+                        slowclk = i;
+                        continue;
+                }
+                min = div_u64((u64)NSEC_PER_SEC * atmel_tc_divisors[i], rate);
+                max = min << tc->tcb_config->counter_width;
+                if (max >= period_ns)
+                        break;
+        }
+
+        /*
+         * If none of the divisor are small enough to represent period_ns
+         * take slow clock (32KHz).
+         */
+        if (i == 5) {
+                i = slowclk;
+                rate = 32768;
+                min = div_u64(NSEC_PER_SEC, rate);
+                max = min << 16;
+
+                /* If period is too big return ERANGE error */
+                if (max < period_ns)
+                        return -ERANGE;
+        }
+
+        duty = div_u64(duty_ns, min);
+        period = div_u64(period_ns, min);
+
+        if (index == 0)
+                atcbpwm = tcbpwmc->pwms[pwm->hwpwm + 1];
+        else
+                atcbpwm = tcbpwmc->pwms[pwm->hwpwm - 1];
+
+        /*
+         * PWM devices provided by TCB driver are grouped by 2:
+         * - group 0: PWM 0 & 1
+         * - group 1: PWM 2 & 3
+         * - group 2: PWM 4 & 5
+         *
+         * PWM devices in a given group must be configured with the
+         * same period_ns.
+         *
+         * We're checking the period value of the second PWM device
+         * in this group before applying the new config.
+         */
+        if ((atcbpwm && atcbpwm->duty > 0 &&
+                        atcbpwm->duty != atcbpwm->period) &&
+                (atcbpwm->div != i || atcbpwm->period != period)) {
+                dev_err(chip->dev,
+                        "failed to configure period_ns: PWM group already configured with a different value\n");
+                return -EINVAL;
+        }
+
+        tcbpwm->period = period;
+        tcbpwm->div = i;
+        tcbpwm->duty = duty;
+
+        /* If the PWM is enabled, call enable to apply the new conf */
+        if (test_bit(PWMF_ENABLED, &pwm->flags))
+                atmel_tcb_pwm_enable(chip, pwm);
+
+        return 0;
+}
+
+static const struct pwm_ops atmel_tcb_pwm_ops = {
+        .request = atmel_tcb_pwm_request,
+        .free = atmel_tcb_pwm_free,
+        .config = atmel_tcb_pwm_config,
+        .set_polarity = atmel_tcb_pwm_set_polarity,
+        .enable = atmel_tcb_pwm_enable,
+        .disable = atmel_tcb_pwm_disable,
+};
+
+static int atmel_tcb_pwm_probe(struct platform_device *pdev)
+{
+        struct atmel_tcb_pwm_chip *tcbpwm;
+        struct device_node *np = pdev->dev.of_node;
+        struct atmel_tc *tc;
+        int err;
+        int tcblock;
+
+        err = of_property_read_u32(np, "tc-block", &tcblock);
+        if (err < 0) {
+                dev_err(&pdev->dev,
+                        "failed to get Timer Counter Block number from device tree (error: %d)\n",
+                        err);
+                return err;
+        }
+
+        tc = atmel_tc_alloc(tcblock, "tcb-pwm");
+        if (tc == NULL) {
+                dev_err(&pdev->dev, "failed to allocate Timer Counter Block\n");
+                return -ENOMEM;
+        }
+
+        tcbpwm = devm_kzalloc(&pdev->dev, sizeof(*tcbpwm), GFP_KERNEL);
+        if (tcbpwm == NULL) {
+                atmel_tc_free(tc);
+                dev_err(&pdev->dev, "failed to allocate memory\n");
+                return -ENOMEM;
+        }
+
+        tcbpwm->chip.dev = &pdev->dev;
+        tcbpwm->chip.ops = &atmel_tcb_pwm_ops;
+        tcbpwm->chip.of_xlate = of_pwm_xlate_with_flags;
+        tcbpwm->chip.of_pwm_n_cells = 3;
+        tcbpwm->chip.base = -1;
+        tcbpwm->chip.npwm = NPWM;
+        tcbpwm->tc = tc;
+
+        spin_lock_init(&tcbpwm->lock);
+
+        err = pwmchip_add(&tcbpwm->chip);
+        if (err < 0) {
+                atmel_tc_free(tc);
+                return err;
+        }
+
+        platform_set_drvdata(pdev, tcbpwm);
+
+        return 0;
+}
+
+static int atmel_tcb_pwm_remove(struct platform_device *pdev)
+{
+        struct atmel_tcb_pwm_chip *tcbpwm = platform_get_drvdata(pdev);
+        int err;
+
+        err = pwmchip_remove(&tcbpwm->chip);
+        if (err < 0)
+                return err;
+
+        atmel_tc_free(tcbpwm->tc);
+
+        return 0;
+}
+
+static const struct of_device_id atmel_tcb_pwm_dt_ids[] = {
+        { .compatible = "atmel,tcb-pwm", },
+        { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, atmel_tcb_pwm_dt_ids);
+
+static struct platform_driver atmel_tcb_pwm_driver = {
+        .driver = {
+                .name = "atmel-tcb-pwm",
+                .of_match_table = atmel_tcb_pwm_dt_ids,
+        },
+        .probe = atmel_tcb_pwm_probe,
+        .remove = atmel_tcb_pwm_remove,
+};
+module_platform_driver(atmel_tcb_pwm_driver);
+
+MODULE_AUTHOR("Boris BREZILLON <b.brezillon@overkiz.com>");
+MODULE_DESCRIPTION("Atmel Timer Counter Pulse Width Modulation Driver");
+MODULE_LICENSE("GPL v2");