前言：
由于网络上关于mt7628和mt7688 pwm相关的资料非常少，所以只能自己慢慢琢磨。虽然研究的心得没有多少，但是其实也是费了不少精力，希望转载文章时，保留出处。佐须之男，专业从事网络设备(路由器)等嵌入式开发和技术咨询工作。
#include <linux/err.h>#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/kernel.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
/* mt7628/mt7688 共有4路原生PWM分别是PWM0，PWM1，PWM3，PWM3。
其中PWM2和PWM3和UART1复用，在使用PWM2和PWM3时需要关闭复用。
*/
/* PWM registers and bits definitions */
#define PWMCON 0x00 /* PWM Conntrol 寄存器 */
#define PWMHDUR 0x04 /* PWM High Duration 寄存器 */
#define PWMLDUR 0x08 /* PWM Low Duration 寄存器 */
#define PWMGDUR 0x0c /* PWM Guard Duration 寄存器 */
#define PWMWAVENUM 0x28 /* PWM Wave Num 寄存器 */
#define PWMDWIDTH 0x2c /* PWM Data Width 寄存器 */
#define PWMTHRES 0x30 /* PWM Thresh 寄存器 */
/**
* struct mtk_pwm_chip - struct representing pwm chip
*
* @mmio_base: base address of pwm chip
* @chip: linux pwm chip representation
*/
struct mtk_pwm_chip {
void __iomem *mmio_base;
struct pwm_chip chip;
};
static inline struct mtk_pwm_chip *to_mtk_pwm_chip(struct pwm_chip *chip)
{
return container_of(chip, struct mtk_pwm_chip, chip);
}
static inline u32 mtk_pwm_readl(struct mtk_pwm_chip *chip, unsigned int num,
unsigned long offset)
{
return ioread32(chip->mmio_base + 0x10 + (num * 0x40) + offset);
}
static inline void mtk_pwm_writel(struct mtk_pwm_chip *chip,
unsigned int num, unsigned long offset,
unsigned long val)
{
iowrite32(val, chip->mmio_base + 0x10 + (num * 0x40) + offset);
}
static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
u32 resolution = 100 / 4;
/* 由于PWM是由40MHZ基准频率分频所得，所以PWM的频率是25ns的倍数关系 perdios_ns = 25*2^clkdiv 0 <= clkdiv <=7 */
u32 clkdiv = 0;
/* 分频倍数分别是 0 1 2 4 8 16 32 64 128 , 所以 0 <= clkdiv <=7 */
while (period_ns / resolution > 8191) {
clkdiv++;
resolution *= 2;
}
if (clkdiv > 7)
return -1;
mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | BIT(3) | clkdiv);
/* 设置控制寄存器，设置基准频率是40MHZ和分频倍数 */
mtk_pwm_writel(pc, pwm->hwpwm, PWMDWIDTH, period_ns / resolution);
/* 设置总周期，T */
mtk_pwm_writel(pc, pwm->hwpwm, PWMTHRES, duty_ns / resolution);
/* 设置上升沿周期t，占空比 = t/T*100 */
return 0;
}
static int mtk_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
u32 val;
val = ioread32(pc->mmio_base);
val |= BIT(pwm->hwpwm);
iowrite32(val, pc->mmio_base);
return 0;
}
static void mtk_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
u32 val;
val = ioread32(pc->mmio_base);
val &= ~BIT(pwm->hwpwm);
iowrite32(val, pc->mmio_base);
}
static const struct pwm_ops mtk_pwm_ops = {
.config = mtk_pwm_config,
.enable = mtk_pwm_enable,
.disable = mtk_pwm_disable,
.owner = THIS_MODULE,
};
static int mtk_pwm_probe(struct platform_device *pdev)
{
struct mtk_pwm_chip *pc;
struct resource *r;
int ret;
pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
if (!pc)
return -ENOMEM;
r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
pc->mmio_base = devm_ioremap_resource(&pdev->dev, r);
if (IS_ERR(pc->mmio_base))
return PTR_ERR(pc->mmio_base);
platform_set_drvdata(pdev, pc);
pc->chip.dev = &pdev->dev;
pc->chip.ops = &mtk_pwm_ops;
pc->chip.base = -1;
pc->chip.npwm = NUM_PWM;
ret = pwmchip_add(&pc->chip);
if (ret < 0)
dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
return ret;
}
static int mtk_pwm_remove(struct platform_device *pdev)
{
struct mtk_pwm_chip *pc = platform_get_drvdata(pdev);
int i;
for (i = 0; i < NUM_PWM; i++)
pwm_disable(&pc->chip.pwms[i]);
return pwmchip_remove(&pc->chip);
}
static const struct of_device_id mtk_pwm_of_match[] = {
{ .compatible = "mediatek,mt7628-pwm" },
{ }
};
MODULE_DEVICE_TABLE(of, mtk_pwm_of_match);
static struct platform_driver mtk_pwm_driver = {
.driver = {
.name = "mtk-pwm",
.owner = THIS_MODULE,
.of_match_table = mtk_pwm_of_match,
},
.probe = mtk_pwm_probe,
.remove = mtk_pwm_remove,
};
module_platform_driver(mtk_pwm_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("John Crispin <blogic@openwrt.org>");
MODULE_ALIAS("platform:mtk-pwm"); 版权所有: http://forgotfun.org/2016/08/MediaTech%28MTK%29+MT7628+MT7688+OpenWRT+%E4%B8%8B+PWM%E9%A9%B1%E5%8A%A8%E7%AE%80%E8%A6%81%E5%88%86%E6%9E%90.html
作者: 佐须之男 未经允许请勿转载