Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
pwm: pca9685: Use bulk write to atomicially update registers
The output of a PWM channel is configured by four register values. Write
them in a single i2c transaction to ensure glitch free updates.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/bfa8c0267c9ec059d0d77f146998d564654c75ca.1753784092.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
authored by
Uwe Kleine-König
and committed by
Uwe Kleine-König
de585561
ca478d8a
+29
-17
+29
-17
drivers/pwm/pwm-pca9685.c
+29
-17
drivers/pwm/pwm-pca9685.c
···
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#define MODE1_SUB2 BIT(2)
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#define MODE1_SUB1 BIT(3)
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#define MODE1_SLEEP BIT(4)
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#define MODE1_AI BIT(5)
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+
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#define MODE2_INVRT BIT(4)
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#define MODE2_OUTDRV BIT(2)
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···
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return err;
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}
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static int pca9685_write_4reg(struct pwm_chip *chip, unsigned int reg, u8 val[4])
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{
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struct pca9685 *pca = to_pca(chip);
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struct device *dev = pwmchip_parent(chip);
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int err;
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err = regmap_bulk_write(pca->regmap, reg, val, 4);
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if (err)
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dev_err(dev, "regmap_write to register 0x%x failed: %pe\n", reg, ERR_PTR(err));
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return err;
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}
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/* Helper function to set the duty cycle ratio to duty/4096 (e.g. duty=2048 -> 50%) */
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static void pca9685_pwm_set_duty(struct pwm_chip *chip, int channel, unsigned int duty)
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{
···
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return;
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} else if (duty >= PCA9685_COUNTER_RANGE) {
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/* Set the full ON bit and clear the full OFF bit */
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pca9685_write_reg(chip, REG_ON_H(channel), LED_FULL);
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pca9685_write_reg(chip, REG_OFF_H(channel), 0);
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pca9685_write_4reg(chip, REG_ON_L(channel), (u8[4]){ 0, LED_FULL, 0, 0 });
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return;
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}
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-
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if (pwm->state.usage_power && channel < PCA9685_MAXCHAN) {
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/*
···
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off = (on + duty) % PCA9685_COUNTER_RANGE;
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/* Set ON time (clears full ON bit) */
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pca9685_write_reg(chip, REG_ON_L(channel), on & 0xff);
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pca9685_write_reg(chip, REG_ON_H(channel), (on >> 8) & 0xf);
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/* Set OFF time (clears full OFF bit) */
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pca9685_write_reg(chip, REG_OFF_L(channel), off & 0xff);
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pca9685_write_reg(chip, REG_OFF_H(channel), (off >> 8) & 0xf);
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/* implicitly clear full ON and full OFF bit */
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pca9685_write_4reg(chip, REG_ON_L(channel),
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(u8[4]){ on & 0xff, (on >> 8) & 0xf, off & 0xff, (off >> 8) & 0xf });
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}
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static unsigned int pca9685_pwm_get_duty(struct pwm_chip *chip, int channel)
···
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mutex_init(&pca->lock);
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ret = pca9685_read_reg(chip, PCA9685_MODE2, ®);
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if (ret)
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return ret;
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/* clear MODE2_OCH */
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reg = 0;
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if (device_property_read_bool(&client->dev, "invert"))
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reg |= MODE2_INVRT;
···
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if (ret)
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return ret;
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/* Disable all LED ALLCALL and SUBx addresses to avoid bus collisions */
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/*
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* Disable all LED ALLCALL and SUBx addresses to avoid bus collisions,
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* enable Auto-Increment.
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*/
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pca9685_read_reg(chip, PCA9685_MODE1, ®);
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reg &= ~(MODE1_ALLCALL | MODE1_SUB1 | MODE1_SUB2 | MODE1_SUB3);
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reg |= MODE1_AI;
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pca9685_write_reg(chip, PCA9685_MODE1, reg);
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/* Reset OFF/ON registers to POR default */
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pca9685_write_reg(chip, PCA9685_ALL_LED_OFF_L, 0);
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pca9685_write_reg(chip, PCA9685_ALL_LED_OFF_H, LED_FULL);
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pca9685_write_reg(chip, PCA9685_ALL_LED_ON_L, 0);
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pca9685_write_reg(chip, PCA9685_ALL_LED_ON_H, LED_FULL);
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ret = pca9685_write_4reg(chip, PCA9685_ALL_LED_ON_L, (u8[]){ 0, LED_FULL, 0, LED_FULL });
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if (ret < 0)
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return dev_err_probe(&client->dev, ret, "Failed to reset ON/OFF registers\n");
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chip->ops = &pca9685_pwm_ops;
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