如何在qualcomm 8960和8921上使用PWM功能 (GPIO24)

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一、PWM 分析

1. PWM: Pulse Width Modulator； LPG： Light Pulse Generator；两者指的是同一东西。

2. PWM driver： /kernel/drivers/mfd/pm8xxx-pwm.c

3. 手机中注册路径： /sys/devices/platform/msm_ssbi.0/pm8921-core/pm8xxx-pwm
4. 利用debugfs调试
   a. #mkdir /data/debugfs
   b. #mount -t debugfs none /data/debugfs
   c. #cd /data/debugfs/pmx8xxx-pwm-dbg
   d. #ls 可以看到共有8路pwm可用
   e. #cd 0; ls
       duty-cycle   //占宽比 (0,100)之间
       enable
       period       //输出波周期 [7, 327*1000000L]微秒之间
   f. 需要先设置period, #echo 50 > period
   g. #echo 50 > duty-cycle

h. #echo 1 > enable

二、调查完成，所需要修改的代码
1. @kernel/arch/arm/mach-msm/board-semc_blue_cdb.c, 设置PM8921的GPIO工作在PWM function
   static struct pm8xxx_gpio_init pm8921_gpios[] __initdata = {
       ...
       //PM8XXX_GPIO_DISABLE(24),
       PM8XXX_GPIO_INIT(   24,
                   PM_GPIO_DIR_OUT,
                   PM_GPIO_OUT_BUF_CMOS,
                   1,
                   PM_GPIO_PULL_NO,
                   PMIC_GPIO_VIN0,
                   PM_GPIO_STRENGTH_HIGH,
                   PM_GPIO_FUNC_2,
                   1,
                   0
               ),
       ...
   }
2. @kernel/arch/arm/mach-msm/board-semc_blue.c, 设置PWM/LPG 的bank1 可用，该bank1 对应的是GPIO24
   static struct pm8xxx_pwm_platform_data pm8xxx_pwm_pdata = {
       //.dtest_channel   = PM8XXX_PWM_DTEST_CHANNEL_NONE,
       .dtest_channel   = 0,
   };
3. 进入手机adb shell
   a. #mount -t debugfs none /data/debugfs
   b. #cd data/debugfs/ pm8xxx-pwm-dbg/0
   c. #echo 2000 > period //必须先设置period, 单位为usecond, 区间为[7, 327*1000000L]us
   d. #echo 50 > duty-cycle //占空比 (0,100)之间
   e. #echo 1 > enable //现在有LPG 方波输出
   f. #echo 1 > enable //取消 LPG 方波输出

三、如何检测PM8921 GPIO 的状态
1. 利用手机系统中已有 /sys/kernel/debug/pm8921-dbg ,gpio检测接口
   a. #echo 0x??? > addr //输入GPIO register addrress
   b. #echo 0x??? > data //输入控制GPIO，写入register 的值
   c. #cat data //查看当前bank输入的值
2. 查看PM8921 register information 文档
   a. Function,Sub funtion,Register name,Register Address,Type,Reset code,default value,comments
        GPIO,   GPIO_24,    GPIO_CNTRL,   0x167,       8B_WR, 5,   00865A01,   Power-off and Power-on default state is Hi-Z
   b. 所以GPIO24的 Register Address 是0x167
3. 检测GPIO24的配置状态,先设置 bank0-7,再读取在该bank设置的参数
   #echo 0x167 > addr
   echo 0x0 > data //选择bank0
   cat data --> 0x01 //得到在bank0 设置的参数
   echo 0x10 > data
   cat data -->0x18
   echo 0x20> data
   cat data -->0x2A
   echo 0x30 > data
   cat data -->0x34
   echo 0x40 > data
   cat data -->0x46
   echo 0x50 > data
   cat data
   echo 0x60 > data
   cat data
   echo 0x70 > data
   cat data
    直接设置某个bank的参数
   #echo 0x167 > addr
   #echo 0xc6 > data //各bit含义： [7]->(1W,0R),[6:4]->Bank Select, [3:0]->各bank含义不一样
   所以0xC6表示0b11000110, 写入,bank4,写入的参数为0110

四，如何用GPIO24模拟 PWM 输出，主要修改kernel/drivers/mfd/pm8xxx-pwm.c

#define TEST_PWM

#ifdef TEST_PWM
#include <linux/mfd/pm8xxx/gpio.h>
#include <linux/delay.h>
#endif

struct pm8xxx_pwm_dbg_device {
   struct mutex       dbg_mutex;
   struct device       *dev;
   struct dentry       *dent;

   struct pm8xxx_pwm_user   *user;

#ifdef TEST_PWM
   struct work_struct pwm_work;
   struct workqueue_struct *pwm_wq;
   bool pwm_run;
#endif
};

#ifdef TEST_PWM
static int dbg_pwm_value_set(void *data, u64 val)
{
   struct pm8xxx_pwm_user      *puser = data;
   struct pm8xxx_pwm_dbg_device    *dbgdev = puser->dbgdev;
   int gpio_sys = 175;//PM8921_GPIO_PM_TO_SYS(24);

   mutex_lock(&dbgdev->dbg_mutex);

   gpio_set_value_cansleep(gpio_sys, val);

   mutex_unlock(&dbgdev->dbg_mutex);

   pr_debug("#### value = %d\n",(int)val);

   return 0;
}

static int dbg_pwm_value_get(void *data, u64 *val)
{
   struct pm8xxx_pwm_user      *puser = data;
   struct pm8xxx_pwm_dbg_device    *dbgdev = puser->dbgdev;
   int gpio_sys = 175;//PM8921_GPIO_PM_TO_SYS(24);

   mutex_lock(&dbgdev->dbg_mutex);

   *val =gpio_get_value_cansleep(gpio_sys);

   mutex_unlock(&dbgdev->dbg_mutex);

   pr_debug("#### value = %d\n",(int)*val);

   return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(dbg_pwm_value_fops,
           dbg_pwm_value_get, dbg_pwm_value_set, "%lld\n");

static void pwm_instant_work(struct work_struct *work)
{
   int gpio_sys = 175;//PM8921_GPIO_PM_TO_SYS(24);
   struct pm8xxx_pwm_dbg_device *dbgdev= container_of(work, struct pm8xxx_pwm_dbg_device, pwm_work);
   struct pm8xxx_pwm_user      *puser;
   int period;
   int duty_cycle;
   int high_us, low_us;

   pr_debug(" ### start output signal\n");

   puser = dbgdev->user;
   period = puser->period;
   duty_cycle = puser->duty_cycle;

   if( !period || !duty_cycle )
       return;

   high_us = period * duty_cycle /100;
   low_us = period - high_us;
   pr_debug("### hight_us = %d, low_us = %d \n ", high_us, low_us);

   while(dbgdev->pwm_run)
   {
       gpio_set_value_cansleep(gpio_sys, 1);
       //usleep(high_us);
       udelay(high_us);

       gpio_set_value_cansleep(gpio_sys, 0);
       //usleep(low_us);
       udelay(low_us);
   }
}

static int dbg_pwm_output_set(void *data, u64 val)
{
   struct pm8xxx_pwm_user      *puser = data;
   struct pm8xxx_pwm_dbg_device    *dbgdev = puser->dbgdev;

   mutex_lock(&dbgdev->dbg_mutex);

   pr_debug("#### value = %d\n",(int)val);

   if( val )
   {
       dbgdev->pwm_run = true;
       queue_work(dbgdev->pwm_wq, &dbgdev->pwm_work);
   }
   else
   {
       dbgdev->pwm_run = false;
   }

   mutex_unlock(&dbgdev->dbg_mutex);

   return 0;
}

static int dbg_pwm_output_get(void *data, u64 *val)
{
   struct pm8xxx_pwm_user      *puser = data;
   struct pm8xxx_pwm_dbg_device    *dbgdev = puser->dbgdev;

   mutex_lock(&dbgdev->dbg_mutex);

   *val = dbgdev->pwm_run;

   mutex_unlock(&dbgdev->dbg_mutex);

   return 0;
}

DEFINE_SIMPLE_ATTRIBUTE(dbg_pwm_output_fops,
           dbg_pwm_output_get, dbg_pwm_output_set, "%lld\n");
#endif

static int __devinit pm8xxx_pwm_dbg_probe(struct device *dev)

{

....

        if (temp == NULL || IS_ERR(temp)) {
           pr_err("ERR: pwm=%d: enable: dent=%p\n", i, dent);
           rc = -ENOMEM;
           goto debug_error;
       }
#ifdef TEST_PWM
       temp = debugfs_create_file("value", S_IRUGO | S_IWUSR,
                       dent, puser, &dbg_pwm_value_fops);
       if (temp == NULL || IS_ERR(temp)) {
           pr_err("ERR: pwm=%d: enable: dent=%p\n", i, dent);
           rc = -ENOMEM;
           goto debug_error;
       }

       temp = debugfs_create_file("output", S_IRUGO | S_IWUSR,
                       dent, puser, &dbg_pwm_output_fops);
       if (temp == NULL || IS_ERR(temp)) {
           pr_err("ERR: pwm=%d: enable: dent=%p\n", i, dent);
           rc = -ENOMEM;
           goto debug_error;
       }
#endif

....

    pmic_dbg_device = dbgdev;

#ifdef TEST_PWM
   dbgdev->pwm_wq = create_singlethread_workqueue("pwm_wq");
   INIT_WORK(&dbgdev->pwm_work, pwm_instant_work);
#endif

   return 0;

....

}