[PATCH v2 0/2] leds: pca955x: Add HW blink support

[PATCH v2 0/2] 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.

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 (2):
  leds: pca955x: Clean up and optimize
  leds: pca955x: Add HW blink support

 drivers/leds/leds-pca955x.c | 340 +++++++++++++++++++++++++-----------
 1 file changed, 236 insertions(+), 104 deletions(-)

-- 
2.27.0

[PATCH v2 1/2] leds: pca955x: Clean up and optimize

[Eddie James]

Clean up the I2C access functions to avoid fetching the pca955x
driver data again. Optimize the probe to do at most 4 reads and
4 writes of the LED selector regs, rather than 16 of each.
Rename some functions and variables to be more consistent and
descriptive.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/leds/leds-pca955x.c | 148 ++++++++++++++++++++----------------
 1 file changed, 82 insertions(+), 66 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index 81aaf21212d7..dd51f40973d8 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -140,13 +140,13 @@ struct pca955x_platform_data {
 };
 
 /* 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;
 }
@@ -161,20 +161,25 @@ 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
  */
-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 = 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);
+	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;
 }
 
@@ -185,16 +190,16 @@ 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 = 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);
+	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;
 }
 
@@ -202,16 +207,16 @@ 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 = 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);
+	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;
 }
 
@@ -219,15 +224,14 @@ 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 = 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);
+	ret = i2c_smbus_read_byte_data(pca955x->client, cmd);
 	if (ret < 0) {
-		dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
+		dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
 			__func__, n, ret);
 		return ret;
 	}
@@ -235,15 +239,14 @@ static int pca955x_read_ls(struct i2c_client *client, int n, u8 *val)
 	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 = 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);
+	ret = i2c_smbus_read_byte_data(pca955x->client, cmd);
 	if (ret < 0) {
-		dev_err(&client->dev, "%s: reg 0x%x, err %d\n",
+		dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
 			__func__, n, ret);
 		return ret;
 	}
@@ -260,12 +263,11 @@ 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;
 
-	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;
@@ -276,7 +278,7 @@ 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;
@@ -289,34 +291,30 @@ 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 = container_of(led_cdev,
+						       struct pca955x_led,
+						       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);
+	ret = pca955x_read_ls(pca955x, reg, &ls);
 	if (ret)
 		goto out;
 
 	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:
 		/*
@@ -326,14 +324,14 @@ 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, ls_led, PCA955X_LS_BLINK1);
+		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);
@@ -492,7 +490,9 @@ 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;
@@ -563,6 +563,15 @@ 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;
@@ -574,21 +583,20 @@ 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;
 
@@ -633,23 +641,31 @@ 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(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

Re: [PATCH v2 1/2] leds: pca955x: Clean up and optimize

[Andy Shevchenko]

On Thu, Apr 7, 2022 at 10:42 PM Eddie James <eajames@linux.ibm.com> wrote:
>
> Clean up the I2C access functions to avoid fetching the pca955x
> driver data again. Optimize the probe to do at most 4 reads and
> 4 writes of the LED selector regs, rather than 16 of each.

> Rename some functions and variables to be more consistent and
> descriptive.

Separate patch.

> +               dev_err(&pca955x->client->dev,
> +                       "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n, val,
> +                       ret);

This can be indented better.

I would add a temporary dev pointer variable and put this on one line.

 struct device *dev = &pca955x->client->dev;

               dev_err(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);

Ditto.

...

> +               dev_err(&pca955x->client->dev,
> +                       "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n, val,
> +                       ret);

Ditto.

...

> +               dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
>                         __func__, n, ret);

Ditto.

...

> +               dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
>                         __func__, n, ret);

Ditto.

...

> +       struct pca955x_led *pca955x_led = container_of(led_cdev,
> +                                                      struct pca955x_led,
> +                                                      led_cdev);

Is it used once? If more than once, consider a helper for that as well.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 1/2] leds: pca955x: Clean up and optimize

[Eddie James]

On 4/8/22 06:11, Andy Shevchenko wrote:
> On Thu, Apr 7, 2022 at 10:42 PM Eddie James <eajames@linux.ibm.com> wrote:
>> Clean up the I2C access functions to avoid fetching the pca955x
>> driver data again. Optimize the probe to do at most 4 reads and
>> 4 writes of the LED selector regs, rather than 16 of each.
>> Rename some functions and variables to be more consistent and
>> descriptive.
> Separate patch.


Ack.



>
>> +               dev_err(&pca955x->client->dev,
>> +                       "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n, val,
>> +                       ret);
> This can be indented better.
>
> I would add a temporary dev pointer variable and put this on one line.
>
>   struct device *dev = &pca955x->client->dev;
>
>                 dev_err(dev, "%s: reg 0x%x, val 0x%x, err %d\n",
> __func__, n, val, ret);


Hm, I still end up having to use two lines for the dev_err function, so 
not sure it's worth it?


>
> ...
>
>> +               dev_err(&pca955x->client->dev,
>> +                       "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n, val,
>> +                       ret);
> Ditto.
>
> ...
>
>> +               dev_err(&pca955x->client->dev,
>> +                       "%s: reg 0x%x, val 0x%x, err %d\n", __func__, n, val,
>> +                       ret);
> Ditto.
>
> ...
>
>> +               dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
>>                          __func__, n, ret);
> Ditto.
>
> ...
>
>> +               dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
>>                          __func__, n, ret);
> Ditto.
>
> ...
>
>> +       struct pca955x_led *pca955x_led = container_of(led_cdev,
>> +                                                      struct pca955x_led,
>> +                                                      led_cdev);
> Is it used once? If more than once, consider a helper for that as well.


Ack.


Thanks for the review!

Eddie

>

[PATCH v2 2/2] 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.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
---
 drivers/leds/leds-pca955x.c | 224 +++++++++++++++++++++++++++---------
 1 file changed, 170 insertions(+), 54 deletions(-)

diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index dd51f40973d8..d1bbcbbaab68 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	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
@@ -168,7 +178,7 @@ 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) / <38 or 44, chip dependent>
  */
 static int pca955x_write_psc(struct pca955x *pca955x, int n, u8 val)
 {
@@ -254,6 +264,21 @@ 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 = container_of(led_cdev,
@@ -275,7 +300,10 @@ 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);
@@ -306,29 +334,36 @@ 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);
@@ -339,6 +374,96 @@ 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 *= (unsigned long)pca955x->chipdef->blink_div;
+	p /= 1000;
+	p -= 1;
+
+	return (u8)p;
+}
+
+static unsigned long pca955x_psc_to_period(struct pca955x *pca955x, u8 psc)
+{
+	unsigned long p = (unsigned long)psc;
+
+	p += 1;
+	p *= 1000;
+	p /= (unsigned long)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 = container_of(led_cdev,
+						      struct pca955x_led,
+						      led_cdev);
+	struct pca955x *pca955x = pca955x_led->pca955x;
+	int ret;
+	unsigned long p = *delay_on + *delay_off;
+
+	mutex_lock(&pca955x->lock);
+
+	if (!p) {
+		p = pca955x->active_blink ? pca955x->blink_period :
+			PCA955X_BLINK_DEFAULT;
+	} else {
+		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;
+		}
+	}
+
+	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.
@@ -494,8 +619,9 @@ 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);
@@ -559,6 +685,7 @@ static int pca955x_probe(struct i2c_client *client)
 	mutex_init(&pca955x->lock);
 	pca955x->client = client;
 	pca955x->chipdef = chip;
+	pca955x->blink_period = PCA955X_BLINK_DEFAULT;
 
 	init_data.devname_mandatory = false;
 	init_data.devicename = "pca955x";
@@ -588,15 +715,21 @@ 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;
 
@@ -624,20 +757,6 @@ 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;
-			}
 		}
 	}
 
@@ -649,22 +768,19 @@ 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) {
+		psc0 = pca955x_period_to_psc(pca955x, pca955x->blink_period);
+		err = pca955x_write_psc(pca955x, 0, psc0);
+	} else {
+		err = pca955x_read_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

Re: [PATCH v2 2/2] leds: pca955x: Add HW blink support

[Andy Shevchenko]

On Thu, Apr 7, 2022 at 10:43 PM Eddie James <eajames@linux.ibm.com> wrote:
>
> 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.

...

> +#define PCA955X_BLINK_DEFAULT  1000

What's the unit of this number?

...

>   * 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) / <38 or 44, chip dependent>

Using <> in  formulas a bit confusing, what about

 * period of the PWM output.  period = (PSCx + 1) / coeff
 * where for ... chips coeff = 38, for ... chips coeff = 44.

?

...

> +               dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
> +                       __func__, n, ret);

Can be indented better. But I would rather see regmap, where this kind
of debugging is for free and already present in the regmap core/.

...

> +static u8 pca955x_period_to_psc(struct pca955x *pca955x, unsigned long p)
> +{
> +       p *= (unsigned long)pca955x->chipdef->blink_div;

Why casting?

> +       p /= 1000;

Does this 1000 have a meaning? (see units.h and other headers with
time / frequency multiplier definitions).

> +       p -= 1;

> +       return (u8)p;

Redundant casting.

> +}

> +static unsigned long pca955x_psc_to_period(struct pca955x *pca955x, u8 psc)
> +{
> +       unsigned long p = (unsigned long)psc;
> +
> +       p += 1;
> +       p *= 1000;
> +       p /= (unsigned long)pca955x->chipdef->blink_div;
> +
> +       return p;

Similar questions here.

> +}

...

> +       if (!p) {

Why not use a positive conditional?

> +               p = pca955x->active_blink ? pca955x->blink_period :
> +                       PCA955X_BLINK_DEFAULT;
> +       } else {
> +               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;
> +               }
> +       }

...

> +       if (!keep_psc0) {

Ditto.

> +               psc0 = pca955x_period_to_psc(pca955x, pca955x->blink_period);
> +               err = pca955x_write_psc(pca955x, 0, psc0);
> +       } else {
> +               err = pca955x_read_psc(pca955x, 0, &psc0);
>         }

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/2] leds: pca955x: Add HW blink support

[Eddie James]

On 4/8/22 06:19, Andy Shevchenko wrote:
> On Thu, Apr 7, 2022 at 10:43 PM Eddie James <eajames@linux.ibm.com> wrote:
>> 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.
> ...
>
>> +#define PCA955X_BLINK_DEFAULT  1000
> What's the unit of this number?


milliseconds, I'll change the name to reflect that.


>
> ...
>
>>    * 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) / <38 or 44, chip dependent>
> Using <> in  formulas a bit confusing, what about
>
>   * period of the PWM output.  period = (PSCx + 1) / coeff
>   * where for ... chips coeff = 38, for ... chips coeff = 44.
>
> ?


Ack.


>
> ...
>
>> +               dev_err(&pca955x->client->dev, "%s: reg 0x%x, err %d\n",
>> +                       __func__, n, ret);
> Can be indented better. But I would rather see regmap, where this kind
> of debugging is for free and already present in the regmap core/.


Agree, but perhaps for a future enhancement?


>
> ...
>
>> +static u8 pca955x_period_to_psc(struct pca955x *pca955x, unsigned long p)
>> +{
>> +       p *= (unsigned long)pca955x->chipdef->blink_div;
> Why casting?


Ack, and all the rest. Will get a v2 up.


Thanks Andy.

Eddie