mbox series

[v3,0/4] leds: pca955x: Add HW blink support

Message ID 20220411162033.39613-1-eajames@linux.ibm.com
Headers show
Series leds: pca955x: Add HW blink support | expand

Message

Eddie James April 11, 2022, 4:20 p.m. UTC 
This series adds support for blinking using the PCA955x chip, falling
back to software blinking if another LED on the chip is already blinking
at a different rate, or if the requested rate isn't representable with
the PCA955x.
Also included are some minor clean up and optimization changes that make
the HW blinking a bit easier.

Changes since v2:
 - Split the cleanup patch
 - Prettier dev_err calls
 - Include units for blink period and use defined unit translations
   rather than just a number.
 - Use positive conditionals.

Changes since v1:
 - Rework the blink function to fallback to software blinking if the
   period is out of range of the chip's capabilities or if another LED
   on the chip is already blinking at a different rate.
 - Add the cleanup patch

Eddie James (4):
  leds: pca955x: Refactor with helper functions and renaming
  leds: pca955x: Use pointers to driver data rather than I2C client
  leds: pca955x: Optimize probe led selection
  leds: pca955x: Add HW blink support

 drivers/leds/leds-pca955x.c | 341 ++++++++++++++++++++++++------------
 1 file changed, 232 insertions(+), 109 deletions(-)

Comments

Pavel Machek May 4, 2022, 5:24 p.m. UTC | #1 
Hi!

> Support blinking using the PCA955x chip. Use PWM0 for blinking
> instead of LED_HALF brightness. Since there is only one frequency
> and brightness register for any blinking LED, track the blink state
> of each LED and only support one HW blinking frequency. If another
> frequency is requested, fallback to software blinking.

WHat happens to LED_HALF support in this case? Could we only do the accelerated blinking
if HALF support is not needed?

Best regards,
									Pavel

> ---
>  drivers/leds/leds-pca955x.c | 222 +++++++++++++++++++++++++++---------
>  1 file changed, 168 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
> index 61f3cb84a945..7c156de215d7 100644
> --- a/drivers/leds/leds-pca955x.c
> +++ b/drivers/leds/leds-pca955x.c
> @@ -62,6 +62,8 @@
>  #define PCA955X_GPIO_HIGH	LED_OFF
>  #define PCA955X_GPIO_LOW	LED_FULL
>  
> +#define PCA955X_BLINK_DEFAULT_MS	1000
> +
>  enum pca955x_type {
>  	pca9550,
>  	pca9551,
> @@ -74,6 +76,7 @@ struct pca955x_chipdef {
>  	int			bits;
>  	u8			slv_addr;	/* 7-bit slave address mask */
>  	int			slv_addr_shift;	/* Number of bits to ignore */
> +	int			blink_div;	/* PSC divider */
>  };
>  
>  static struct pca955x_chipdef pca955x_chipdefs[] = {
> @@ -81,26 +84,31 @@ static struct pca955x_chipdef pca955x_chipdefs[] = {
>  		.bits		= 2,
>  		.slv_addr	= /* 110000x */ 0x60,
>  		.slv_addr_shift	= 1,
> +		.blink_div	= 44,
>  	},
>  	[pca9551] = {
>  		.bits		= 8,
>  		.slv_addr	= /* 1100xxx */ 0x60,
>  		.slv_addr_shift	= 3,
> +		.blink_div	= 38,
>  	},
>  	[pca9552] = {
>  		.bits		= 16,
>  		.slv_addr	= /* 1100xxx */ 0x60,
>  		.slv_addr_shift	= 3,
> +		.blink_div	= 44,
>  	},
>  	[ibm_pca9552] = {
>  		.bits		= 16,
>  		.slv_addr	= /* 0110xxx */ 0x30,
>  		.slv_addr_shift	= 3,
> +		.blink_div	= 44,
>  	},
>  	[pca9553] = {
>  		.bits		= 4,
>  		.slv_addr	= /* 110001x */ 0x62,
>  		.slv_addr_shift	= 1,
> +		.blink_div	= 44,
>  	},
>  };
>  
> @@ -119,7 +127,9 @@ struct pca955x {
>  	struct pca955x_led *leds;
>  	struct pca955x_chipdef	*chipdef;
>  	struct i2c_client	*client;
> +	unsigned long active_blink;
>  	unsigned long active_pins;
> +	unsigned long blink_period;
>  #ifdef CONFIG_LEDS_PCA955X_GPIO
>  	struct gpio_chip gpio;
>  #endif
> @@ -170,7 +180,8 @@ static inline int pca955x_ledstate(u8 ls, int led_num)
>  
>  /*
>   * Write to frequency prescaler register, used to program the
> - * period of the PWM output.  period = (PSCx + 1) / 38
> + * period of the PWM output.  period = (PSCx + 1) / coeff
> + * Where for pca9551 chips coeff = 38 and for all other chips coeff = 44
>   */
>  static int pca955x_write_psc(struct pca955x *pca955x, int n, u8 val)
>  {
> @@ -251,6 +262,20 @@ static int pca955x_read_pwm(struct pca955x *pca955x, int n, u8 *val)
>  	return 0;
>  }
>  
> +static int pca955x_read_psc(struct pca955x *pca955x, int n, u8 *val)
> +{
> +	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + (2 * n);
> +	int ret;
> +
> +	ret = i2c_smbus_read_byte_data(pca955x->client, cmd);
> +	if (ret < 0) {
> +		dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n", __func__, n, ret);
> +		return ret;
> +	}
> +	*val = (u8)ret;
> +	return 0;
> +}
> +
>  static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
>  {
>  	struct pca955x_led *pca955x_led = led_to_pca955x(led_cdev);
> @@ -270,7 +295,10 @@ static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
>  		ret = LED_OFF;
>  		break;
>  	case PCA955X_LS_BLINK0:
> -		ret = LED_HALF;
> +		ret = pca955x_read_pwm(pca955x, 0, &pwm);
> +		if (ret)
> +			return ret;
> +		ret = 256 - pwm;
>  		break;
>  	case PCA955X_LS_BLINK1:
>  		ret = pca955x_read_pwm(pca955x, 1, &pwm);
> @@ -299,29 +327,36 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
>  	if (ret)
>  		goto out;
>  
> -	switch (value) {
> -	case LED_FULL:
> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_ON);
> -		break;
> -	case LED_OFF:
> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_OFF);
> -		break;
> -	case LED_HALF:
> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK0);
> -		break;
> -	default:
> -		/*
> -		 * Use PWM1 for all other values.  This has the unwanted
> -		 * side effect of making all LEDs on the chip share the
> -		 * same brightness level if set to a value other than
> -		 * OFF, HALF, or FULL.  But, this is probably better than
> -		 * just turning off for all other values.
> -		 */
> -		ret = pca955x_write_pwm(pca955x, 1, 255 - value);
> -		if (ret)
> +	if (test_bit(pca955x_led->led_num, &pca955x->active_blink)) {
> +		if (value == LED_OFF) {
> +			clear_bit(pca955x_led->led_num, &pca955x->active_blink);
> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_OFF);
> +		} else {
> +			ret = pca955x_write_pwm(pca955x, 0, 256 - value);
>  			goto out;
> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK1);
> -		break;
> +		}
> +	} else {
> +		switch (value) {
> +		case LED_FULL:
> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_ON);
> +			break;
> +		case LED_OFF:
> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_OFF);
> +			break;
> +		default:
> +			/*
> +			 * Use PWM1 for all other values. This has the unwanted
> +			 * side effect of making all LEDs on the chip share the
> +			 * same brightness level if set to a value other than
> +			 * OFF or FULL. But, this is probably better than just
> +			 * turning off for all other values.
> +			 */
> +			ret = pca955x_write_pwm(pca955x, 1, 255 - value);
> +			if (ret)
> +				goto out;
> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK1);
> +			break;
> +		}
>  	}
>  
>  	ret = pca955x_write_ls(pca955x, reg, ls);
> @@ -332,6 +367,94 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
>  	return ret;
>  }
>  
> +static u8 pca955x_period_to_psc(struct pca955x *pca955x, unsigned long p)
> +{
> +	p *= pca955x->chipdef->blink_div;
> +	p /= MSEC_PER_SEC;
> +	p -= 1;
> +
> +	return p;
> +}
> +
> +static unsigned long pca955x_psc_to_period(struct pca955x *pca955x, u8 psc)
> +{
> +	unsigned long p = psc;
> +
> +	p += 1;
> +	p *= MSEC_PER_SEC;
> +	p /= pca955x->chipdef->blink_div;
> +
> +	return p;
> +}
> +
> +static int pca955x_led_blink(struct led_classdev *led_cdev,
> +			     unsigned long *delay_on, unsigned long *delay_off)
> +{
> +	struct pca955x_led *pca955x_led = led_to_pca955x(led_cdev);
> +	struct pca955x *pca955x = pca955x_led->pca955x;
> +	unsigned long p = *delay_on + *delay_off;
> +	int ret;
> +
> +	mutex_lock(&pca955x->lock);
> +
> +	if (p) {
> +		if (*delay_on != *delay_off) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +
> +		if (p < pca955x_psc_to_period(pca955x, 0) ||
> +		    p > pca955x_psc_to_period(pca955x, 0xff)) {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +	} else {
> +		p = pca955x->active_blink ? pca955x->blink_period :
> +			PCA955X_BLINK_DEFAULT_MS;
> +	}
> +
> +	if (!pca955x->active_blink ||
> +	    pca955x->active_blink == BIT(pca955x_led->led_num) ||
> +	    pca955x->blink_period == p) {
> +		u8 psc = pca955x_period_to_psc(pca955x, p);
> +
> +		if (!test_and_set_bit(pca955x_led->led_num,
> +				      &pca955x->active_blink)) {
> +			u8 ls;
> +			int reg = pca955x_led->led_num / 4;
> +			int bit = pca955x_led->led_num % 4;
> +
> +			ret = pca955x_read_ls(pca955x, reg, &ls);
> +			if (ret)
> +				goto out;
> +
> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK0);
> +			ret = pca955x_write_ls(pca955x, reg, ls);
> +			if (ret)
> +				goto out;
> +		}
> +
> +		if (pca955x->blink_period != p) {
> +			pca955x->blink_period = p;
> +			ret = pca955x_write_psc(pca955x, 0, psc);
> +			if (ret)
> +				goto out;
> +		}
> +
> +		p = pca955x_psc_to_period(pca955x, psc);
> +		p /= 2;
> +		*delay_on = p;
> +		*delay_off = p;
> +	} else {
> +		ret = -EBUSY;
> +	}
> +
> +out:
> +	mutex_unlock(&pca955x->lock);
> +
> +	return ret;
> +}
> +
>  #ifdef CONFIG_LEDS_PCA955X_GPIO
>  /*
>   * Read the INPUT register, which contains the state of LEDs.
> @@ -487,8 +610,9 @@ static int pca955x_probe(struct i2c_client *client)
>  	u8 ls1[4];
>  	u8 ls2[4];
>  	struct pca955x_platform_data *pdata;
> +	u8 psc0;
> +	bool keep_psc0 = false;
>  	bool set_default_label = false;
> -	bool keep_pwm = false;
>  	char default_label[8];
>  	enum pca955x_type chip_type;
>  	const void *md = device_get_match_data(&client->dev);
> @@ -552,6 +676,7 @@ static int pca955x_probe(struct i2c_client *client)
>  	mutex_init(&pca955x->lock);
>  	pca955x->client = client;
>  	pca955x->chipdef = chip;
> +	pca955x->blink_period = PCA955X_BLINK_DEFAULT_MS;
>  
>  	init_data.devname_mandatory = false;
>  	init_data.devicename = "pca955x";
> @@ -581,15 +706,21 @@ static int pca955x_probe(struct i2c_client *client)
>  			led = &pca955x_led->led_cdev;
>  			led->brightness_set_blocking = pca955x_led_set;
>  			led->brightness_get = pca955x_led_get;
> +			led->blink_set = pca955x_led_blink;
>  
>  			if (pdata->leds[i].default_state ==
> -			    LEDS_GPIO_DEFSTATE_OFF)
> +			    LEDS_GPIO_DEFSTATE_OFF) {
>  				ls2[reg] = pca955x_ledsel(ls2[reg], bit,
>  							  PCA955X_LS_LED_OFF);
> -			else if (pdata->leds[i].default_state ==
> -				   LEDS_GPIO_DEFSTATE_ON)
> +			} else if (pdata->leds[i].default_state ==
> +				   LEDS_GPIO_DEFSTATE_ON) {
>  				ls2[reg] = pca955x_ledsel(ls2[reg], bit,
>  							  PCA955X_LS_LED_ON);
> +			} else if (pca955x_ledstate(ls2[reg], bit) ==
> +				   PCA955X_LS_BLINK0) {
> +				keep_psc0 = true;
> +				set_bit(i, &pca955x->active_blink);
> +			}
>  
>  			init_data.fwnode = pdata->leds[i].fwnode;
>  
> @@ -617,20 +748,6 @@ static int pca955x_probe(struct i2c_client *client)
>  				return err;
>  
>  			set_bit(i, &pca955x->active_pins);
> -
> -			/*
> -			 * For default-state == "keep", let the core update the
> -			 * brightness from the hardware, then check the
> -			 * brightness to see if it's using PWM1. If so, PWM1
> -			 * should not be written below.
> -			 */
> -			if (pdata->leds[i].default_state ==
> -			    LEDS_GPIO_DEFSTATE_KEEP) {
> -				if (led->brightness != LED_FULL &&
> -				    led->brightness != LED_OFF &&
> -				    led->brightness != LED_HALF)
> -					keep_pwm = true;
> -			}
>  		}
>  	}
>  
> @@ -642,22 +759,19 @@ static int pca955x_probe(struct i2c_client *client)
>  		}
>  	}
>  
> -	/* PWM0 is used for half brightness or 50% duty cycle */
> -	err = pca955x_write_pwm(pca955x, 0, 255 - LED_HALF);
> -	if (err)
> -		return err;
> -
> -	if (!keep_pwm) {
> -		/* PWM1 is used for variable brightness, default to OFF */
> -		err = pca955x_write_pwm(pca955x, 1, 0);
> -		if (err)
> -			return err;
> +	if (keep_psc0) {
> +		err = pca955x_read_psc(pca955x, 0, &psc0);
> +	} else {
> +		psc0 = pca955x_period_to_psc(pca955x, pca955x->blink_period);
> +		err = pca955x_write_psc(pca955x, 0, psc0);
>  	}
>  
> -	/* Set to fast frequency so we do not see flashing */
> -	err = pca955x_write_psc(pca955x, 0, 0);
>  	if (err)
>  		return err;
> +
> +	pca955x->blink_period = pca955x_psc_to_period(pca955x, psc0);
> +
> +	/* Set PWM1 to fast frequency so we do not see flashing */
>  	err = pca955x_write_psc(pca955x, 1, 0);
>  	if (err)
>  		return err;
> -- 
> 2.27.0
Eddie James May 11, 2022, 7:54 p.m. UTC | #2 
On 5/4/22 12:24, Pavel Machek wrote:
> Hi!
>
>> Support blinking using the PCA955x chip. Use PWM0 for blinking
>> instead of LED_HALF brightness. Since there is only one frequency
>> and brightness register for any blinking LED, track the blink state
>> of each LED and only support one HW blinking frequency. If another
>> frequency is requested, fallback to software blinking.
> WHat happens to LED_HALF support in this case? Could we only do the accelerated blinking
> if HALF support is not needed?


Yes, we lose LED_HALF support in this case. Basically, only full 
brightness is supported for HW blinking leds. The other channel 
(non-blinking) can support any brightness, but of course only for 1 led 
or all leds.


Thanks,

Eddie


>
> Best regards,
> 									Pavel
>
>> ---
>>   drivers/leds/leds-pca955x.c | 222 +++++++++++++++++++++++++++---------
>>   1 file changed, 168 insertions(+), 54 deletions(-)
>>
>> diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
>> index 61f3cb84a945..7c156de215d7 100644
>> --- a/drivers/leds/leds-pca955x.c
>> +++ b/drivers/leds/leds-pca955x.c
>> @@ -62,6 +62,8 @@
>>   #define PCA955X_GPIO_HIGH	LED_OFF
>>   #define PCA955X_GPIO_LOW	LED_FULL
>>   
>> +#define PCA955X_BLINK_DEFAULT_MS	1000
>> +
>>   enum pca955x_type {
>>   	pca9550,
>>   	pca9551,
>> @@ -74,6 +76,7 @@ struct pca955x_chipdef {
>>   	int			bits;
>>   	u8			slv_addr;	/* 7-bit slave address mask */
>>   	int			slv_addr_shift;	/* Number of bits to ignore */
>> +	int			blink_div;	/* PSC divider */
>>   };
>>   
>>   static struct pca955x_chipdef pca955x_chipdefs[] = {
>> @@ -81,26 +84,31 @@ static struct pca955x_chipdef pca955x_chipdefs[] = {
>>   		.bits		= 2,
>>   		.slv_addr	= /* 110000x */ 0x60,
>>   		.slv_addr_shift	= 1,
>> +		.blink_div	= 44,
>>   	},
>>   	[pca9551] = {
>>   		.bits		= 8,
>>   		.slv_addr	= /* 1100xxx */ 0x60,
>>   		.slv_addr_shift	= 3,
>> +		.blink_div	= 38,
>>   	},
>>   	[pca9552] = {
>>   		.bits		= 16,
>>   		.slv_addr	= /* 1100xxx */ 0x60,
>>   		.slv_addr_shift	= 3,
>> +		.blink_div	= 44,
>>   	},
>>   	[ibm_pca9552] = {
>>   		.bits		= 16,
>>   		.slv_addr	= /* 0110xxx */ 0x30,
>>   		.slv_addr_shift	= 3,
>> +		.blink_div	= 44,
>>   	},
>>   	[pca9553] = {
>>   		.bits		= 4,
>>   		.slv_addr	= /* 110001x */ 0x62,
>>   		.slv_addr_shift	= 1,
>> +		.blink_div	= 44,
>>   	},
>>   };
>>   
>> @@ -119,7 +127,9 @@ struct pca955x {
>>   	struct pca955x_led *leds;
>>   	struct pca955x_chipdef	*chipdef;
>>   	struct i2c_client	*client;
>> +	unsigned long active_blink;
>>   	unsigned long active_pins;
>> +	unsigned long blink_period;
>>   #ifdef CONFIG_LEDS_PCA955X_GPIO
>>   	struct gpio_chip gpio;
>>   #endif
>> @@ -170,7 +180,8 @@ static inline int pca955x_ledstate(u8 ls, int led_num)
>>   
>>   /*
>>    * Write to frequency prescaler register, used to program the
>> - * period of the PWM output.  period = (PSCx + 1) / 38
>> + * period of the PWM output.  period = (PSCx + 1) / coeff
>> + * Where for pca9551 chips coeff = 38 and for all other chips coeff = 44
>>    */
>>   static int pca955x_write_psc(struct pca955x *pca955x, int n, u8 val)
>>   {
>> @@ -251,6 +262,20 @@ static int pca955x_read_pwm(struct pca955x *pca955x, int n, u8 *val)
>>   	return 0;
>>   }
>>   
>> +static int pca955x_read_psc(struct pca955x *pca955x, int n, u8 *val)
>> +{
>> +	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + (2 * n);
>> +	int ret;
>> +
>> +	ret = i2c_smbus_read_byte_data(pca955x->client, cmd);
>> +	if (ret < 0) {
>> +		dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n", __func__, n, ret);
>> +		return ret;
>> +	}
>> +	*val = (u8)ret;
>> +	return 0;
>> +}
>> +
>>   static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
>>   {
>>   	struct pca955x_led *pca955x_led = led_to_pca955x(led_cdev);
>> @@ -270,7 +295,10 @@ static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
>>   		ret = LED_OFF;
>>   		break;
>>   	case PCA955X_LS_BLINK0:
>> -		ret = LED_HALF;
>> +		ret = pca955x_read_pwm(pca955x, 0, &pwm);
>> +		if (ret)
>> +			return ret;
>> +		ret = 256 - pwm;
>>   		break;
>>   	case PCA955X_LS_BLINK1:
>>   		ret = pca955x_read_pwm(pca955x, 1, &pwm);
>> @@ -299,29 +327,36 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
>>   	if (ret)
>>   		goto out;
>>   
>> -	switch (value) {
>> -	case LED_FULL:
>> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_ON);
>> -		break;
>> -	case LED_OFF:
>> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_OFF);
>> -		break;
>> -	case LED_HALF:
>> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK0);
>> -		break;
>> -	default:
>> -		/*
>> -		 * Use PWM1 for all other values.  This has the unwanted
>> -		 * side effect of making all LEDs on the chip share the
>> -		 * same brightness level if set to a value other than
>> -		 * OFF, HALF, or FULL.  But, this is probably better than
>> -		 * just turning off for all other values.
>> -		 */
>> -		ret = pca955x_write_pwm(pca955x, 1, 255 - value);
>> -		if (ret)
>> +	if (test_bit(pca955x_led->led_num, &pca955x->active_blink)) {
>> +		if (value == LED_OFF) {
>> +			clear_bit(pca955x_led->led_num, &pca955x->active_blink);
>> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_OFF);
>> +		} else {
>> +			ret = pca955x_write_pwm(pca955x, 0, 256 - value);
>>   			goto out;
>> -		ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK1);
>> -		break;
>> +		}
>> +	} else {
>> +		switch (value) {
>> +		case LED_FULL:
>> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_ON);
>> +			break;
>> +		case LED_OFF:
>> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_OFF);
>> +			break;
>> +		default:
>> +			/*
>> +			 * Use PWM1 for all other values. This has the unwanted
>> +			 * side effect of making all LEDs on the chip share the
>> +			 * same brightness level if set to a value other than
>> +			 * OFF or FULL. But, this is probably better than just
>> +			 * turning off for all other values.
>> +			 */
>> +			ret = pca955x_write_pwm(pca955x, 1, 255 - value);
>> +			if (ret)
>> +				goto out;
>> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK1);
>> +			break;
>> +		}
>>   	}
>>   
>>   	ret = pca955x_write_ls(pca955x, reg, ls);
>> @@ -332,6 +367,94 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
>>   	return ret;
>>   }
>>   
>> +static u8 pca955x_period_to_psc(struct pca955x *pca955x, unsigned long p)
>> +{
>> +	p *= pca955x->chipdef->blink_div;
>> +	p /= MSEC_PER_SEC;
>> +	p -= 1;
>> +
>> +	return p;
>> +}
>> +
>> +static unsigned long pca955x_psc_to_period(struct pca955x *pca955x, u8 psc)
>> +{
>> +	unsigned long p = psc;
>> +
>> +	p += 1;
>> +	p *= MSEC_PER_SEC;
>> +	p /= pca955x->chipdef->blink_div;
>> +
>> +	return p;
>> +}
>> +
>> +static int pca955x_led_blink(struct led_classdev *led_cdev,
>> +			     unsigned long *delay_on, unsigned long *delay_off)
>> +{
>> +	struct pca955x_led *pca955x_led = led_to_pca955x(led_cdev);
>> +	struct pca955x *pca955x = pca955x_led->pca955x;
>> +	unsigned long p = *delay_on + *delay_off;
>> +	int ret;
>> +
>> +	mutex_lock(&pca955x->lock);
>> +
>> +	if (p) {
>> +		if (*delay_on != *delay_off) {
>> +			ret = -EINVAL;
>> +			goto out;
>> +		}
>> +
>> +		if (p < pca955x_psc_to_period(pca955x, 0) ||
>> +		    p > pca955x_psc_to_period(pca955x, 0xff)) {
>> +			ret = -EINVAL;
>> +			goto out;
>> +		}
>> +	} else {
>> +		p = pca955x->active_blink ? pca955x->blink_period :
>> +			PCA955X_BLINK_DEFAULT_MS;
>> +	}
>> +
>> +	if (!pca955x->active_blink ||
>> +	    pca955x->active_blink == BIT(pca955x_led->led_num) ||
>> +	    pca955x->blink_period == p) {
>> +		u8 psc = pca955x_period_to_psc(pca955x, p);
>> +
>> +		if (!test_and_set_bit(pca955x_led->led_num,
>> +				      &pca955x->active_blink)) {
>> +			u8 ls;
>> +			int reg = pca955x_led->led_num / 4;
>> +			int bit = pca955x_led->led_num % 4;
>> +
>> +			ret = pca955x_read_ls(pca955x, reg, &ls);
>> +			if (ret)
>> +				goto out;
>> +
>> +			ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK0);
>> +			ret = pca955x_write_ls(pca955x, reg, ls);
>> +			if (ret)
>> +				goto out;
>> +		}
>> +
>> +		if (pca955x->blink_period != p) {
>> +			pca955x->blink_period = p;
>> +			ret = pca955x_write_psc(pca955x, 0, psc);
>> +			if (ret)
>> +				goto out;
>> +		}
>> +
>> +		p = pca955x_psc_to_period(pca955x, psc);
>> +		p /= 2;
>> +		*delay_on = p;
>> +		*delay_off = p;
>> +	} else {
>> +		ret = -EBUSY;
>> +	}
>> +
>> +out:
>> +	mutex_unlock(&pca955x->lock);
>> +
>> +	return ret;
>> +}
>> +
>>   #ifdef CONFIG_LEDS_PCA955X_GPIO
>>   /*
>>    * Read the INPUT register, which contains the state of LEDs.
>> @@ -487,8 +610,9 @@ static int pca955x_probe(struct i2c_client *client)
>>   	u8 ls1[4];
>>   	u8 ls2[4];
>>   	struct pca955x_platform_data *pdata;
>> +	u8 psc0;
>> +	bool keep_psc0 = false;
>>   	bool set_default_label = false;
>> -	bool keep_pwm = false;
>>   	char default_label[8];
>>   	enum pca955x_type chip_type;
>>   	const void *md = device_get_match_data(&client->dev);
>> @@ -552,6 +676,7 @@ static int pca955x_probe(struct i2c_client *client)
>>   	mutex_init(&pca955x->lock);
>>   	pca955x->client = client;
>>   	pca955x->chipdef = chip;
>> +	pca955x->blink_period = PCA955X_BLINK_DEFAULT_MS;
>>   
>>   	init_data.devname_mandatory = false;
>>   	init_data.devicename = "pca955x";
>> @@ -581,15 +706,21 @@ static int pca955x_probe(struct i2c_client *client)
>>   			led = &pca955x_led->led_cdev;
>>   			led->brightness_set_blocking = pca955x_led_set;
>>   			led->brightness_get = pca955x_led_get;
>> +			led->blink_set = pca955x_led_blink;
>>   
>>   			if (pdata->leds[i].default_state ==
>> -			    LEDS_GPIO_DEFSTATE_OFF)
>> +			    LEDS_GPIO_DEFSTATE_OFF) {
>>   				ls2[reg] = pca955x_ledsel(ls2[reg], bit,
>>   							  PCA955X_LS_LED_OFF);
>> -			else if (pdata->leds[i].default_state ==
>> -				   LEDS_GPIO_DEFSTATE_ON)
>> +			} else if (pdata->leds[i].default_state ==
>> +				   LEDS_GPIO_DEFSTATE_ON) {
>>   				ls2[reg] = pca955x_ledsel(ls2[reg], bit,
>>   							  PCA955X_LS_LED_ON);
>> +			} else if (pca955x_ledstate(ls2[reg], bit) ==
>> +				   PCA955X_LS_BLINK0) {
>> +				keep_psc0 = true;
>> +				set_bit(i, &pca955x->active_blink);
>> +			}
>>   
>>   			init_data.fwnode = pdata->leds[i].fwnode;
>>   
>> @@ -617,20 +748,6 @@ static int pca955x_probe(struct i2c_client *client)
>>   				return err;
>>   
>>   			set_bit(i, &pca955x->active_pins);
>> -
>> -			/*
>> -			 * For default-state == "keep", let the core update the
>> -			 * brightness from the hardware, then check the
>> -			 * brightness to see if it's using PWM1. If so, PWM1
>> -			 * should not be written below.
>> -			 */
>> -			if (pdata->leds[i].default_state ==
>> -			    LEDS_GPIO_DEFSTATE_KEEP) {
>> -				if (led->brightness != LED_FULL &&
>> -				    led->brightness != LED_OFF &&
>> -				    led->brightness != LED_HALF)
>> -					keep_pwm = true;
>> -			}
>>   		}
>>   	}
>>   
>> @@ -642,22 +759,19 @@ static int pca955x_probe(struct i2c_client *client)
>>   		}
>>   	}
>>   
>> -	/* PWM0 is used for half brightness or 50% duty cycle */
>> -	err = pca955x_write_pwm(pca955x, 0, 255 - LED_HALF);
>> -	if (err)
>> -		return err;
>> -
>> -	if (!keep_pwm) {
>> -		/* PWM1 is used for variable brightness, default to OFF */
>> -		err = pca955x_write_pwm(pca955x, 1, 0);
>> -		if (err)
>> -			return err;
>> +	if (keep_psc0) {
>> +		err = pca955x_read_psc(pca955x, 0, &psc0);
>> +	} else {
>> +		psc0 = pca955x_period_to_psc(pca955x, pca955x->blink_period);
>> +		err = pca955x_write_psc(pca955x, 0, psc0);
>>   	}
>>   
>> -	/* Set to fast frequency so we do not see flashing */
>> -	err = pca955x_write_psc(pca955x, 0, 0);
>>   	if (err)
>>   		return err;
>> +
>> +	pca955x->blink_period = pca955x_psc_to_period(pca955x, psc0);
>> +
>> +	/* Set PWM1 to fast frequency so we do not see flashing */
>>   	err = pca955x_write_psc(pca955x, 1, 0);
>>   	if (err)
>>   		return err;
>> -- 
>> 2.27.0