[PATCH v5 0/4] leds: pca955x: Add HW blink support

[PATCH v5 0/4] leds: pca955x: Add HW blink support

[Eddie James]

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 v4:
 - Set duty cycle to fifty percent for blinked LEDs in order to maintain
   the specified blink rate.

Changes since v3:
 - Initialize return value in the blink function
   Thanks Dan Carpenter and kernel test robot

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 | 348 ++++++++++++++++++++++++------------
 1 file changed, 237 insertions(+), 111 deletions(-)

-- 
2.27.0

[PATCH v5 1/4] leds: pca955x: Refactor with helper functions and renaming

[Eddie James]

Add helper functions to clean up the code, and rename a few
oddly named functions and variables.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/leds/leds-pca955x.c | 50 ++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 26 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index 81aaf21212d7..a683c872e1ff 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -134,19 +134,21 @@ struct pca955x_led {
 	struct fwnode_handle	*fwnode;
 };
 
+#define led_to_pca955x(l)	container_of(l, struct pca955x_led, led_cdev)
+
 struct pca955x_platform_data {
 	struct pca955x_led	*leds;
 	int			num_leds;
 };
 
 /* 8 bits per input register */
-static inline int pca95xx_num_input_regs(int bits)
+static inline int pca955x_num_input_regs(int bits)
 {
 	return (bits + 7) / 8;
 }
 
 /* 4 bits per LED selector register */
-static inline int pca95xx_num_led_regs(int bits)
+static inline int pca955x_num_led_regs(int bits)
 {
 	return (bits + 3)  / 4;
 }
@@ -161,6 +163,11 @@ static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
 		((state & 0x3) << (led_num << 1));
 }
 
+static inline int pca955x_ledstate(u8 ls, int led_num)
+{
+	return (ls >> (led_num << 1)) & 0x3;
+}
+
 /*
  * Write to frequency prescaler register, used to program the
  * period of the PWM output.  period = (PSCx + 1) / 38
@@ -168,7 +175,7 @@ static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
 static int pca955x_write_psc(struct i2c_client *client, int n, u8 val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
-	u8 cmd = pca95xx_num_input_regs(pca955x->chipdef->bits) + (2 * n);
+	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + (2 * n);
 	int ret;
 
 	ret = i2c_smbus_write_byte_data(client, cmd, val);
@@ -188,7 +195,7 @@ static int pca955x_write_psc(struct i2c_client *client, int n, u8 val)
 static int pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
-	u8 cmd = pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + (2 * n);
+	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 1 + (2 * n);
 	int ret;
 
 	ret = i2c_smbus_write_byte_data(client, cmd, val);
@@ -205,7 +212,7 @@ static int pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
 static int pca955x_write_ls(struct i2c_client *client, int n, u8 val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
-	u8 cmd = pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n;
+	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 4 + n;
 	int ret;
 
 	ret = i2c_smbus_write_byte_data(client, cmd, val);
@@ -222,7 +229,7 @@ static int pca955x_write_ls(struct i2c_client *client, int n, u8 val)
 static int pca955x_read_ls(struct i2c_client *client, int n, u8 *val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
-	u8 cmd = pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n;
+	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 4 + n;
 	int ret;
 
 	ret = i2c_smbus_read_byte_data(client, cmd);
@@ -238,7 +245,7 @@ static int pca955x_read_ls(struct i2c_client *client, int n, u8 *val)
 static int pca955x_read_pwm(struct i2c_client *client, int n, u8 *val)
 {
 	struct pca955x *pca955x = i2c_get_clientdata(client);
-	u8 cmd = pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + (2 * n);
+	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 1 + (2 * n);
 	int ret;
 
 	ret = i2c_smbus_read_byte_data(client, cmd);
@@ -253,9 +260,7 @@ static int pca955x_read_pwm(struct i2c_client *client, int n, u8 *val)
 
 static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
 {
-	struct pca955x_led *pca955x_led = container_of(led_cdev,
-						       struct pca955x_led,
-						       led_cdev);
+	struct pca955x_led *pca955x_led = led_to_pca955x(led_cdev);
 	struct pca955x *pca955x = pca955x_led->pca955x;
 	u8 ls, pwm;
 	int ret;
@@ -264,8 +269,7 @@ static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
 	if (ret)
 		return ret;
 
-	ls = (ls >> ((pca955x_led->led_num % 4) << 1)) & 0x3;
-	switch (ls) {
+	switch (pca955x_ledstate(ls, pca955x_led->led_num % 4)) {
 	case PCA955X_LS_LED_ON:
 		ret = LED_FULL;
 		break;
@@ -289,19 +293,13 @@ static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
 static int pca955x_led_set(struct led_classdev *led_cdev,
 			    enum led_brightness value)
 {
-	struct pca955x_led *pca955x_led;
-	struct pca955x *pca955x;
+	struct pca955x_led *pca955x_led = led_to_pca955x(led_cdev);
+	struct pca955x *pca955x = pca955x_led->pca955x;
+	int reg = pca955x_led->led_num / 4;
+	int bit = pca955x_led->led_num % 4;
 	u8 ls;
-	int chip_ls;	/* which LSx to use (0-3 potentially) */
-	int ls_led;	/* which set of bits within LSx to use (0-3) */
 	int ret;
 
-	pca955x_led = container_of(led_cdev, struct pca955x_led, led_cdev);
-	pca955x = pca955x_led->pca955x;
-
-	chip_ls = pca955x_led->led_num / 4;
-	ls_led = pca955x_led->led_num % 4;
-
 	mutex_lock(&pca955x->lock);
 
 	ret = pca955x_read_ls(pca955x->client, chip_ls, &ls);
@@ -310,13 +308,13 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
 
 	switch (value) {
 	case LED_FULL:
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_ON);
+		ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_ON);
 		break;
 	case LED_OFF:
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_OFF);
+		ls = pca955x_ledsel(ls, bit, PCA955X_LS_LED_OFF);
 		break;
 	case LED_HALF:
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK0);
+		ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK0);
 		break;
 	default:
 		/*
@@ -329,7 +327,7 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
 		ret = pca955x_write_pwm(pca955x->client, 1, 255 - value);
 		if (ret)
 			goto out;
-		ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
+		ls = pca955x_ledsel(ls, bit, PCA955X_LS_BLINK1);
 		break;
 	}
 
-- 
2.27.0

[PATCH v5 2/4] leds: pca955x: Use pointers to driver data rather than I2C client

[Eddie James]

As a minor clean up item, pass the driver data pointer instead of the
I2C client to the reader and writer helper functions. Now the PCA
driver data doesn't have to be looked up again in the I2C client data

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/leds/leds-pca955x.c | 61 ++++++++++++++++---------------------
 1 file changed, 27 insertions(+), 34 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index a683c872e1ff..cb1895b79eab 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -172,16 +172,15 @@ 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
  */
-static int pca955x_write_psc(struct i2c_client *client, int n, u8 val)
+static int pca955x_write_psc(struct pca955x *pca955x, int n, u8 val)
 {
-	struct pca955x *pca955x = i2c_get_clientdata(client);
 	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + (2 * n);
 	int ret;
 
-	ret = i2c_smbus_write_byte_data(client, cmd, val);
+	ret = i2c_smbus_write_byte_data(pca955x->client, cmd, val);
 	if (ret < 0)
-		dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
-			__func__, n, val, ret);
+		dev_err(&pca955x->client->dev, "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n,
+			val, ret);
 	return ret;
 }
 
@@ -192,16 +191,15 @@ static int pca955x_write_psc(struct i2c_client *client, int n, u8 val)
  *
  * Duty cycle is (256 - PWMx) / 256
  */
-static int pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
+static int pca955x_write_pwm(struct pca955x *pca955x, int n, u8 val)
 {
-	struct pca955x *pca955x = i2c_get_clientdata(client);
 	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 1 + (2 * n);
 	int ret;
 
-	ret = i2c_smbus_write_byte_data(client, cmd, val);
+	ret = i2c_smbus_write_byte_data(pca955x->client, cmd, val);
 	if (ret < 0)
-		dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
-			__func__, n, val, ret);
+		dev_err(&pca955x->client->dev, "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n,
+			val, ret);
 	return ret;
 }
 
@@ -209,16 +207,15 @@ static int pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
  * Write to LED selector register, which determines the source that
  * drives the LED output.
  */
-static int pca955x_write_ls(struct i2c_client *client, int n, u8 val)
+static int pca955x_write_ls(struct pca955x *pca955x, int n, u8 val)
 {
-	struct pca955x *pca955x = i2c_get_clientdata(client);
 	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 4 + n;
 	int ret;
 
-	ret = i2c_smbus_write_byte_data(client, cmd, val);
+	ret = i2c_smbus_write_byte_data(pca955x->client, cmd, val);
 	if (ret < 0)
-		dev_err(&client->dev, "%s: reg 0x%x, val 0x%x, err %d\n",
-			__func__, n, val, ret);
+		dev_err(&pca955x->client->dev, "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n,
+			val, ret);
 	return ret;
 }
 
@@ -226,32 +223,28 @@ static int pca955x_write_ls(struct i2c_client *client, int n, u8 val)
  * Read the LED selector register, which determines the source that
  * drives the LED output.
  */
-static int pca955x_read_ls(struct i2c_client *client, int n, u8 *val)
+static int pca955x_read_ls(struct pca955x *pca955x, int n, u8 *val)
 {
-	struct pca955x *pca955x = i2c_get_clientdata(client);
 	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 4 + n;
 	int ret;
 
-	ret = i2c_smbus_read_byte_data(client, cmd);
+	ret = i2c_smbus_read_byte_data(pca955x->client, cmd);
 	if (ret < 0) {
-		dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
-			__func__, n, ret);
+		dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n", __func__, n, ret);
 		return ret;
 	}
 	*val = (u8)ret;
 	return 0;
 }
 
-static int pca955x_read_pwm(struct i2c_client *client, int n, u8 *val)
+static int pca955x_read_pwm(struct pca955x *pca955x, int n, u8 *val)
 {
-	struct pca955x *pca955x = i2c_get_clientdata(client);
 	u8 cmd = pca955x_num_input_regs(pca955x->chipdef->bits) + 1 + (2 * n);
 	int ret;
 
-	ret = i2c_smbus_read_byte_data(client, cmd);
+	ret = i2c_smbus_read_byte_data(pca955x->client, cmd);
 	if (ret < 0) {
-		dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
-			__func__, n, ret);
+		dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n", __func__, n, ret);
 		return ret;
 	}
 	*val = (u8)ret;
@@ -265,7 +258,7 @@ static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
 	u8 ls, pwm;
 	int ret;
 
-	ret = pca955x_read_ls(pca955x->client, pca955x_led->led_num / 4, &ls);
+	ret = pca955x_read_ls(pca955x, pca955x_led->led_num / 4, &ls);
 	if (ret)
 		return ret;
 
@@ -280,7 +273,7 @@ static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
 		ret = LED_HALF;
 		break;
 	case PCA955X_LS_BLINK1:
-		ret = pca955x_read_pwm(pca955x->client, 1, &pwm);
+		ret = pca955x_read_pwm(pca955x, 1, &pwm);
 		if (ret)
 			return ret;
 		ret = 255 - pwm;
@@ -302,7 +295,7 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
 
 	mutex_lock(&pca955x->lock);
 
-	ret = pca955x_read_ls(pca955x->client, chip_ls, &ls);
+	ret = pca955x_read_ls(pca955x, reg, &ls);
 	if (ret)
 		goto out;
 
@@ -324,14 +317,14 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
 		 * OFF, HALF, or FULL.  But, this is probably better than
 		 * just turning off for all other values.
 		 */
-		ret = pca955x_write_pwm(pca955x->client, 1, 255 - value);
+		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->client, chip_ls, ls);
+	ret = pca955x_write_ls(pca955x, reg, ls);
 
 out:
 	mutex_unlock(&pca955x->lock);
@@ -632,22 +625,22 @@ static int pca955x_probe(struct i2c_client *client)
 	}
 
 	/* PWM0 is used for half brightness or 50% duty cycle */
-	err = pca955x_write_pwm(client, 0, 255 - LED_HALF);
+	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(client, 1, 0);
+		err = pca955x_write_pwm(pca955x, 1, 0);
 		if (err)
 			return err;
 	}
 
 	/* Set to fast frequency so we do not see flashing */
-	err = pca955x_write_psc(client, 0, 0);
+	err = pca955x_write_psc(pca955x, 0, 0);
 	if (err)
 		return err;
-	err = pca955x_write_psc(client, 1, 0);
+	err = pca955x_write_psc(pca955x, 1, 0);
 	if (err)
 		return err;
 
-- 
2.27.0

[PATCH v5 3/4] leds: pca955x: Optimize probe led selection

[Eddie James]

Previously, the probe function might do up to 32 reads and writes
to the same 4 registers to program the led selection. Reduce this to
a maximum of 8 operations by accumulating the changes to the led
selection and comparing with the previous value to write the
selection if different.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/leds/leds-pca955x.c | 40 +++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index cb1895b79eab..61f3cb84a945 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -483,7 +483,9 @@ static int pca955x_probe(struct i2c_client *client)
 	struct led_classdev *led;
 	struct led_init_data init_data;
 	struct i2c_adapter *adapter;
-	int i, err;
+	int i, bit, err, nls, reg;
+	u8 ls1[4];
+	u8 ls2[4];
 	struct pca955x_platform_data *pdata;
 	bool set_default_label = false;
 	bool keep_pwm = false;
@@ -554,6 +556,15 @@ static int pca955x_probe(struct i2c_client *client)
 	init_data.devname_mandatory = false;
 	init_data.devicename = "pca955x";
 
+	nls = pca955x_num_led_regs(chip->bits);
+	for (i = 0; i < nls; ++i) {
+		err = pca955x_read_ls(pca955x, i, &ls1[i]);
+		if (err)
+			return err;
+
+		ls2[i] = ls1[i];
+	}
+
 	for (i = 0; i < chip->bits; i++) {
 		pca955x_led = &pca955x->leds[i];
 		pca955x_led->led_num = i;
@@ -565,21 +576,20 @@ static int pca955x_probe(struct i2c_client *client)
 		case PCA955X_TYPE_GPIO:
 			break;
 		case PCA955X_TYPE_LED:
+			bit = i % 4;
+			reg = i / 4;
 			led = &pca955x_led->led_cdev;
 			led->brightness_set_blocking = pca955x_led_set;
 			led->brightness_get = pca955x_led_get;
 
 			if (pdata->leds[i].default_state ==
-			    LEDS_GPIO_DEFSTATE_OFF) {
-				err = pca955x_led_set(led, LED_OFF);
-				if (err)
-					return err;
-			} else if (pdata->leds[i].default_state ==
-				   LEDS_GPIO_DEFSTATE_ON) {
-				err = pca955x_led_set(led, LED_FULL);
-				if (err)
-					return err;
-			}
+			    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)
+				ls2[reg] = pca955x_ledsel(ls2[reg], bit,
+							  PCA955X_LS_LED_ON);
 
 			init_data.fwnode = pdata->leds[i].fwnode;
 
@@ -624,6 +634,14 @@ static int pca955x_probe(struct i2c_client *client)
 		}
 	}
 
+	for (i = 0; i < nls; ++i) {
+		if (ls1[i] != ls2[i]) {
+			err = pca955x_write_ls(pca955x, i, ls2[i]);
+			if (err)
+				return err;
+		}
+	}
+
 	/* PWM0 is used for half brightness or 50% duty cycle */
 	err = pca955x_write_pwm(pca955x, 0, 255 - LED_HALF);
 	if (err)
-- 
2.27.0

[PATCH v5 4/4] leds: pca955x: Add HW blink support

[Eddie James]

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. In addition,
blinked LEDs can only use full brightness in order to maintain 50%
duty cycle, which is required for the specified blink rate.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/leds/leds-pca955x.c | 229 +++++++++++++++++++++++++++---------
 1 file changed, 173 insertions(+), 56 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index 61f3cb84a945..da93f04e4d10 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);
@@ -264,14 +289,12 @@ static enum led_brightness pca955x_led_get(struct led_classdev *led_cdev)
 
 	switch (pca955x_ledstate(ls, pca955x_led->led_num % 4)) {
 	case PCA955X_LS_LED_ON:
+	case PCA955X_LS_BLINK0:
 		ret = LED_FULL;
 		break;
 	case PCA955X_LS_LED_OFF:
 		ret = LED_OFF;
 		break;
-	case PCA955X_LS_BLINK0:
-		ret = LED_HALF;
-		break;
 	case PCA955X_LS_BLINK1:
 		ret = pca955x_read_pwm(pca955x, 1, &pwm);
 		if (ret)
@@ -299,29 +322,36 @@ 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 {
+			/* No variable brightness for blinking LEDs */
 			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 +362,102 @@ 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 = 0;
+
+	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;
+
+			/*
+			 * Force 50% duty cycle to maintain the specified
+			 * blink rate.
+			 */
+			ret = pca955x_write_pwm(pca955x, 0, 128);
+			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 +613,9 @@ 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 +679,7 @@ 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 +709,21 @@ 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 +751,6 @@ 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 +762,19 @@ 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