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pwm: Add BCM2835 PWM driver
Add PWM driver for Broadcom BCM2835 processor (Raspberry Pi) Signed-off-by: Bart Tanghe <[email protected]> Acked-by: Stephen Warren <[email protected]> Signed-off-by: Thierry Reding <[email protected]>
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‎Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt

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BCM2835 PWM controller (Raspberry Pi controller)
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Required properties:
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- compatible: should be "brcm,bcm2835-pwm"
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- reg: physical base address and length of the controller's registers
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- clock: This clock defines the base clock frequency of the PWM hardware
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system, the period and the duty_cycle of the PWM signal is a multiple of
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the base period.
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- #pwm-cells: Should be 2. See pwm.txt in this directory for a description of
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the cells format.
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Examples:
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pwm@2020c000 {
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compatible = "brcm,bcm2835-pwm";
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reg = <0x2020c000 0x28>;
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clocks = <&clk_pwm>;
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#pwm-cells = <2>;
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};
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clocks {
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....
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clk_pwm: pwm {
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compatible = "fixed-clock";
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reg = <3>;
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#clock-cells = <0>;
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clock-frequency = <9200000>;
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};
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....
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};

‎drivers/pwm/Kconfig

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@@ -71,6 +71,15 @@ config PWM_BCM_KONA
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To compile this driver as a module, choose M here: the module
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will be called pwm-bcm-kona.
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config PWM_BCM2835
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tristate "BCM2835 PWM support"
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depends on ARCH_BCM2835
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help
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PWM framework driver for BCM2835 controller (Raspberry Pi)
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To compile this driver as a module, choose M here: the module
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will be called pwm-bcm2835.
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config PWM_BFIN
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tristate "Blackfin PWM support"
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depends on BFIN_GPTIMERS

‎drivers/pwm/Makefile

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@@ -4,6 +4,7 @@ obj-$(CONFIG_PWM_AB8500) += pwm-ab8500.o
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obj-$(CONFIG_PWM_ATMEL) += pwm-atmel.o
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obj-$(CONFIG_PWM_ATMEL_TCB) += pwm-atmel-tcb.o
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obj-$(CONFIG_PWM_BCM_KONA) += pwm-bcm-kona.o
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obj-$(CONFIG_PWM_BCM2835) += pwm-bcm2835.o
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obj-$(CONFIG_PWM_BFIN) += pwm-bfin.o
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obj-$(CONFIG_PWM_CLPS711X) += pwm-clps711x.o
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obj-$(CONFIG_PWM_EP93XX) += pwm-ep93xx.o

‎drivers/pwm/pwm-bcm2835.c

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/*
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* Copyright 2014 Bart Tanghe <[email protected]>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; version 2.
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*/
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#include <linux/clk.h>
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#include <linux/err.h>
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#include <linux/io.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/pwm.h>
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#define PWM_CONTROL 0x000
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#define PWM_CONTROL_SHIFT(x) ((x) * 8)
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#define PWM_CONTROL_MASK 0xff
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#define PWM_MODE 0x80 /* set timer in PWM mode */
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#define PWM_ENABLE (1 << 0)
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#define PWM_POLARITY (1 << 4)
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#define PERIOD(x) (((x) * 0x10) + 0x10)
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#define DUTY(x) (((x) * 0x10) + 0x14)
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#define MIN_PERIOD 108 /* 9.2 MHz max. PWM clock */
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struct bcm2835_pwm {
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struct pwm_chip chip;
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struct device *dev;
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unsigned long scaler;
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void __iomem *base;
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struct clk *clk;
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};
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static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
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{
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return container_of(chip, struct bcm2835_pwm, chip);
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}
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static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
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{
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struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
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u32 value;
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value = readl(pc->base + PWM_CONTROL);
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value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
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value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
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writel(value, pc->base + PWM_CONTROL);
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return 0;
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}
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static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
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{
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struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
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u32 value;
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value = readl(pc->base + PWM_CONTROL);
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value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
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writel(value, pc->base + PWM_CONTROL);
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}
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static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
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int duty_ns, int period_ns)
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{
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struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
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if (period_ns <= MIN_PERIOD) {
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dev_err(pc->dev, "period %d not supported, minimum %d\n",
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period_ns, MIN_PERIOD);
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return -EINVAL;
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}
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writel(duty_ns / pc->scaler, pc->base + DUTY(pwm->hwpwm));
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writel(period_ns / pc->scaler, pc->base + PERIOD(pwm->hwpwm));
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return 0;
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}
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static int bcm2835_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
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{
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struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
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u32 value;
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value = readl(pc->base + PWM_CONTROL);
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value |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
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writel(value, pc->base + PWM_CONTROL);
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return 0;
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}
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static void bcm2835_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
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{
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struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
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u32 value;
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value = readl(pc->base + PWM_CONTROL);
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value &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
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writel(value, pc->base + PWM_CONTROL);
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}
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static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
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enum pwm_polarity polarity)
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{
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struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
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u32 value;
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value = readl(pc->base + PWM_CONTROL);
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if (polarity == PWM_POLARITY_NORMAL)
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value &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
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else
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value |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
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writel(value, pc->base + PWM_CONTROL);
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return 0;
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}
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static const struct pwm_ops bcm2835_pwm_ops = {
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.request = bcm2835_pwm_request,
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.free = bcm2835_pwm_free,
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.config = bcm2835_pwm_config,
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.enable = bcm2835_pwm_enable,
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.disable = bcm2835_pwm_disable,
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.set_polarity = bcm2835_set_polarity,
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.owner = THIS_MODULE,
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};
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static int bcm2835_pwm_probe(struct platform_device *pdev)
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{
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struct bcm2835_pwm *pc;
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struct resource *res;
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int ret;
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pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
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if (!pc)
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return -ENOMEM;
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pc->dev = &pdev->dev;
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
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pc->base = devm_ioremap_resource(&pdev->dev, res);
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if (IS_ERR(pc->base))
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return PTR_ERR(pc->base);
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pc->clk = devm_clk_get(&pdev->dev, NULL);
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if (IS_ERR(pc->clk)) {
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dev_err(&pdev->dev, "clock not found: %ld\n", PTR_ERR(pc->clk));
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return PTR_ERR(pc->clk);
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}
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ret = clk_prepare_enable(pc->clk);
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if (ret)
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return ret;
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pc->scaler = NSEC_PER_SEC / clk_get_rate(pc->clk);
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pc->chip.dev = &pdev->dev;
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pc->chip.ops = &bcm2835_pwm_ops;
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pc->chip.npwm = 2;
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platform_set_drvdata(pdev, pc);
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ret = pwmchip_add(&pc->chip);
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if (ret < 0)
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goto add_fail;
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return 0;
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add_fail:
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clk_disable_unprepare(pc->clk);
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return ret;
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}
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static int bcm2835_pwm_remove(struct platform_device *pdev)
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{
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struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
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clk_disable_unprepare(pc->clk);
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return pwmchip_remove(&pc->chip);
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}
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static const struct of_device_id bcm2835_pwm_of_match[] = {
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{ .compatible = "brcm,bcm2835-pwm", },
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{ /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
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static struct platform_driver bcm2835_pwm_driver = {
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.driver = {
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.name = "bcm2835-pwm",
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.of_match_table = bcm2835_pwm_of_match,
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},
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.probe = bcm2835_pwm_probe,
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.remove = bcm2835_pwm_remove,
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};
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module_platform_driver(bcm2835_pwm_driver);
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MODULE_AUTHOR("Bart Tanghe <[email protected]");
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MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
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MODULE_LICENSE("GPL v2");

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