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path: root/drivers/pwm/pwm-bcm2835.c
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Diffstat (limited to 'drivers/pwm/pwm-bcm2835.c')
-rw-r--r--drivers/pwm/pwm-bcm2835.c203
1 files changed, 203 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
new file mode 100644
index 0000000000..bdfc2a5ec0
--- /dev/null
+++ b/drivers/pwm/pwm-bcm2835.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2014 Bart Tanghe <bart.tanghe@thomasmore.be>
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#define PWM_CONTROL 0x000
+#define PWM_CONTROL_SHIFT(x) ((x) * 8)
+#define PWM_CONTROL_MASK 0xff
+#define PWM_MODE 0x80 /* set timer in PWM mode */
+#define PWM_ENABLE (1 << 0)
+#define PWM_POLARITY (1 << 4)
+
+#define PERIOD(x) (((x) * 0x10) + 0x10)
+#define DUTY(x) (((x) * 0x10) + 0x14)
+
+#define PERIOD_MIN 0x2
+
+struct bcm2835_pwm {
+ struct pwm_chip chip;
+ struct device *dev;
+ void __iomem *base;
+ struct clk *clk;
+};
+
+static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
+{
+ return container_of(chip, struct bcm2835_pwm, chip);
+}
+
+static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ u32 value;
+
+ value = readl(pc->base + PWM_CONTROL);
+ value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
+ value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
+ writel(value, pc->base + PWM_CONTROL);
+
+ return 0;
+}
+
+static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ u32 value;
+
+ value = readl(pc->base + PWM_CONTROL);
+ value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
+ writel(value, pc->base + PWM_CONTROL);
+}
+
+static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ const struct pwm_state *state)
+{
+
+ struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+ unsigned long rate = clk_get_rate(pc->clk);
+ unsigned long long period_cycles;
+ u64 max_period;
+
+ u32 val;
+
+ if (!rate) {
+ dev_err(pc->dev, "failed to get clock rate\n");
+ return -EINVAL;
+ }
+
+ /*
+ * period_cycles must be a 32 bit value, so period * rate / NSEC_PER_SEC
+ * must be <= U32_MAX. As U32_MAX * NSEC_PER_SEC < U64_MAX the
+ * multiplication period * rate doesn't overflow.
+ * To calculate the maximal possible period that guarantees the
+ * above inequality:
+ *
+ * round(period * rate / NSEC_PER_SEC) <= U32_MAX
+ * <=> period * rate / NSEC_PER_SEC < U32_MAX + 0.5
+ * <=> period * rate < (U32_MAX + 0.5) * NSEC_PER_SEC
+ * <=> period < ((U32_MAX + 0.5) * NSEC_PER_SEC) / rate
+ * <=> period < ((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate
+ * <=> period <= ceil((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate) - 1
+ */
+ max_period = DIV_ROUND_UP_ULL((u64)U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC / 2, rate) - 1;
+
+ if (state->period > max_period)
+ return -EINVAL;
+
+ /* set period */
+ period_cycles = DIV_ROUND_CLOSEST_ULL(state->period * rate, NSEC_PER_SEC);
+
+ /* don't accept a period that is too small */
+ if (period_cycles < PERIOD_MIN)
+ return -EINVAL;
+
+ writel(period_cycles, pc->base + PERIOD(pwm->hwpwm));
+
+ /* set duty cycle */
+ val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * rate, NSEC_PER_SEC);
+ writel(val, pc->base + DUTY(pwm->hwpwm));
+
+ /* set polarity */
+ val = readl(pc->base + PWM_CONTROL);
+
+ if (state->polarity == PWM_POLARITY_NORMAL)
+ val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
+ else
+ val |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
+
+ /* enable/disable */
+ if (state->enabled)
+ val |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
+ else
+ val &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
+
+ writel(val, pc->base + PWM_CONTROL);
+
+ return 0;
+}
+
+static const struct pwm_ops bcm2835_pwm_ops = {
+ .request = bcm2835_pwm_request,
+ .free = bcm2835_pwm_free,
+ .apply = bcm2835_pwm_apply,
+ .owner = THIS_MODULE,
+};
+
+static int bcm2835_pwm_probe(struct platform_device *pdev)
+{
+ struct bcm2835_pwm *pc;
+ int ret;
+
+ pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
+ if (!pc)
+ return -ENOMEM;
+
+ pc->dev = &pdev->dev;
+
+ pc->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(pc->base))
+ return PTR_ERR(pc->base);
+
+ pc->clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(pc->clk))
+ return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
+ "clock not found\n");
+
+ ret = clk_prepare_enable(pc->clk);
+ if (ret)
+ return ret;
+
+ pc->chip.dev = &pdev->dev;
+ pc->chip.ops = &bcm2835_pwm_ops;
+ pc->chip.npwm = 2;
+
+ platform_set_drvdata(pdev, pc);
+
+ ret = pwmchip_add(&pc->chip);
+ if (ret < 0)
+ goto add_fail;
+
+ return 0;
+
+add_fail:
+ clk_disable_unprepare(pc->clk);
+ return ret;
+}
+
+static void bcm2835_pwm_remove(struct platform_device *pdev)
+{
+ struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
+
+ pwmchip_remove(&pc->chip);
+
+ clk_disable_unprepare(pc->clk);
+}
+
+static const struct of_device_id bcm2835_pwm_of_match[] = {
+ { .compatible = "brcm,bcm2835-pwm", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
+
+static struct platform_driver bcm2835_pwm_driver = {
+ .driver = {
+ .name = "bcm2835-pwm",
+ .of_match_table = bcm2835_pwm_of_match,
+ },
+ .probe = bcm2835_pwm_probe,
+ .remove_new = bcm2835_pwm_remove,
+};
+module_platform_driver(bcm2835_pwm_driver);
+
+MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be>");
+MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
+MODULE_LICENSE("GPL v2");