leds: rgb: leds-qcom-lpg: Add support for high resolution PWM

Certain PMICs like PMK8550 have a high resolution PWM module which can
support from 8-bit to 15-bit PWM. Add support for it.
Signed-off-by: Anjelique Melendez <quic_amelende@quicinc.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230407223849.17623-3-quic_amelende@quicinc.com

drivers/leds/rgb/leds-qcom-lpg.c

@@ -2,6 +2,7 @@
 /*
  * Copyright (c) 2017-2022 Linaro Ltd
  * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2023, Qualcomm Innovation Center, Inc. All rights reserved.
  */
 #include <linux/bits.h>
 #include <linux/bitfield.h>
@@ -17,10 +18,13 @@
 #define LPG_SUBTYPE_REG		0x05
 #define  LPG_SUBTYPE_LPG	0x2
 #define  LPG_SUBTYPE_PWM	0xb
+#define  LPG_SUBTYPE_HI_RES_PWM	0xc
 #define  LPG_SUBTYPE_LPG_LITE	0x11
 #define LPG_PATTERN_CONFIG_REG	0x40
 #define LPG_SIZE_CLK_REG	0x41
 #define  PWM_CLK_SELECT_MASK	GENMASK(1, 0)
+#define  PWM_CLK_SELECT_HI_RES_MASK	GENMASK(2, 0)
+#define  PWM_SIZE_HI_RES_MASK	GENMASK(6, 4)
 #define LPG_PREDIV_CLK_REG	0x42
 #define  PWM_FREQ_PRE_DIV_MASK	GENMASK(6, 5)
 #define  PWM_FREQ_EXP_MASK	GENMASK(2, 0)
@@ -43,8 +47,10 @@
 #define LPG_LUT_REG(x)		(0x40 + (x) * 2)
 #define RAMP_CONTROL_REG	0xc8
 
-#define LPG_RESOLUTION		512
+#define LPG_RESOLUTION_9BIT	BIT(9)
+#define LPG_RESOLUTION_15BIT	BIT(15)
 #define LPG_MAX_M		7
+#define LPG_MAX_PREDIV		6
 
 struct lpg_channel;
 struct lpg_data;
@@ -106,6 +112,7 @@ struct lpg {
  * @clk_sel:	reference clock frequency selector
  * @pre_div_sel: divider selector of the reference clock
  * @pre_div_exp: exponential divider of the reference clock
+ * @pwm_resolution_sel:	pwm resolution selector
  * @ramp_enabled: duty cycle is driven by iterating over lookup table
  * @ramp_ping_pong: reverse through pattern, rather than wrapping to start
  * @ramp_oneshot: perform only a single pass over the pattern
@@ -138,6 +145,7 @@ struct lpg_channel {
 	unsigned int clk_sel;
 	unsigned int pre_div_sel;
 	unsigned int pre_div_exp;
+	unsigned int pwm_resolution_sel;
 
 	bool ramp_enabled;
 	bool ramp_ping_pong;
@@ -253,17 +261,24 @@ static int lpg_lut_sync(struct lpg *lpg, unsigned int mask)
 }
 
 static const unsigned int lpg_clk_rates[] = {0, 1024, 32768, 19200000};
+static const unsigned int lpg_clk_rates_hi_res[] = {0, 1024, 32768, 19200000, 76800000};
 static const unsigned int lpg_pre_divs[] = {1, 3, 5, 6};
+static const unsigned int lpg_pwm_resolution[] =  {9};
+static const unsigned int lpg_pwm_resolution_hi_res[] =  {8, 9, 10, 11, 12, 13, 14, 15};
 
 static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period)
 {
-	unsigned int clk_sel, best_clk = 0;
+	unsigned int i, pwm_resolution_count, best_pwm_resolution_sel = 0;
+	const unsigned int *clk_rate_arr, *pwm_resolution_arr;
+	unsigned int clk_sel, clk_len, best_clk = 0;
 	unsigned int div, best_div = 0;
 	unsigned int m, best_m = 0;
+	unsigned int resolution;
 	unsigned int error;
 	unsigned int best_err = UINT_MAX;
+	u64 max_period, min_period;
 	u64 best_period = 0;
-	u64 max_period;
+	u64 max_res;
 
 	/*
 	 * The PWM period is determined by:
@@ -272,73 +287,107 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period)
 	 * period = --------------------------
 	 *                   refclk
 	 *
-	 * With resolution fixed at 2^9 bits, pre_div = {1, 3, 5, 6} and
+	 * Resolution = 2^9 bits for PWM or
+	 *              2^{8, 9, 10, 11, 12, 13, 14, 15} bits for high resolution PWM
+	 * pre_div = {1, 3, 5, 6} and
 	 * M = [0..7].
 	 *
-	 * This allows for periods between 27uS and 384s, as the PWM framework
-	 * wants a period of equal or lower length than requested, reject
-	 * anything below 27uS.
+	 * This allows for periods between 27uS and 384s for PWM channels and periods between
+	 * 3uS and 24576s for high resolution PWMs.
+	 * The PWM framework wants a period of equal or lower length than requested,
+	 * reject anything below minimum period.
 	 */
-	if (period <= (u64)NSEC_PER_SEC * LPG_RESOLUTION / 19200000)
+
+	if (chan->subtype == LPG_SUBTYPE_HI_RES_PWM) {
+		clk_rate_arr = lpg_clk_rates_hi_res;
+		clk_len = ARRAY_SIZE(lpg_clk_rates_hi_res);
+		pwm_resolution_arr = lpg_pwm_resolution_hi_res;
+		pwm_resolution_count = ARRAY_SIZE(lpg_pwm_resolution_hi_res);
+		max_res = LPG_RESOLUTION_15BIT;
+	} else {
+		clk_rate_arr = lpg_clk_rates;
+		clk_len = ARRAY_SIZE(lpg_clk_rates);
+		pwm_resolution_arr = lpg_pwm_resolution;
+		pwm_resolution_count = ARRAY_SIZE(lpg_pwm_resolution);
+		max_res = LPG_RESOLUTION_9BIT;
+	}
+
+	min_period = (u64)NSEC_PER_SEC *
+			div64_u64((1 << pwm_resolution_arr[0]), clk_rate_arr[clk_len - 1]);
+	if (period <= min_period)
 		return -EINVAL;
 
 	/* Limit period to largest possible value, to avoid overflows */
-	max_period = (u64)NSEC_PER_SEC * LPG_RESOLUTION * 6 * (1 << LPG_MAX_M) / 1024;
+	max_period = (u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV *
+			div64_u64((1 << LPG_MAX_M), 1024);
 	if (period > max_period)
 		period = max_period;
 
 	/*
-	 * Search for the pre_div, refclk and M by solving the rewritten formula
-	 * for each refclk and pre_div value:
+	 * Search for the pre_div, refclk, resolution and M by solving the rewritten formula
+	 * for each refclk, resolution and pre_div value:
 	 *
 	 *                     period * refclk
 	 * M = log2 -------------------------------------
 	 *           NSEC_PER_SEC * pre_div * resolution
 	 */
-	for (clk_sel = 1; clk_sel < ARRAY_SIZE(lpg_clk_rates); clk_sel++) {
-		u64 numerator = period * lpg_clk_rates[clk_sel];
-
-		for (div = 0; div < ARRAY_SIZE(lpg_pre_divs); div++) {
-			u64 denominator = (u64)NSEC_PER_SEC * lpg_pre_divs[div] * LPG_RESOLUTION;
-			u64 actual;
-			u64 ratio;
-
-			if (numerator < denominator)
-				continue;
-
-			ratio = div64_u64(numerator, denominator);
-			m = ilog2(ratio);
-			if (m > LPG_MAX_M)
-				m = LPG_MAX_M;
-
-			actual = DIV_ROUND_UP_ULL(denominator * (1 << m), lpg_clk_rates[clk_sel]);
-
-			error = period - actual;
-			if (error < best_err) {
-				best_err = error;
 
-				best_div = div;
-				best_m = m;
-				best_clk = clk_sel;
-				best_period = actual;
+	for (i = 0; i < pwm_resolution_count; i++) {
+		resolution = 1 << pwm_resolution_arr[i];
+		for (clk_sel = 1; clk_sel < clk_len; clk_sel++) {
+			u64 numerator = period * clk_rate_arr[clk_sel];
+
+			for (div = 0; div < ARRAY_SIZE(lpg_pre_divs); div++) {
+				u64 denominator = (u64)NSEC_PER_SEC * lpg_pre_divs[div] *
+						  resolution;
+				u64 actual;
+				u64 ratio;
+
+				if (numerator < denominator)
+					continue;
+
+				ratio = div64_u64(numerator, denominator);
+				m = ilog2(ratio);
+				if (m > LPG_MAX_M)
+					m = LPG_MAX_M;
+
+				actual = DIV_ROUND_UP_ULL(denominator * (1 << m),
+							  clk_rate_arr[clk_sel]);
+				error = period - actual;
+				if (error < best_err) {
+					best_err = error;
+					best_div = div;
+					best_m = m;
+					best_clk = clk_sel;
+					best_period = actual;
+					best_pwm_resolution_sel = i;
+				}
 			}
 		}
 	}
-
 	chan->clk_sel = best_clk;
 	chan->pre_div_sel = best_div;
 	chan->pre_div_exp = best_m;
 	chan->period = best_period;
-
+	chan->pwm_resolution_sel = best_pwm_resolution_sel;
 	return 0;
 }
 
 static void lpg_calc_duty(struct lpg_channel *chan, uint64_t duty)
 {
-	unsigned int max = LPG_RESOLUTION - 1;
+	unsigned int max;
 	unsigned int val;
+	unsigned int clk_rate;
+
+	if (chan->subtype == LPG_SUBTYPE_HI_RES_PWM) {
+		max = LPG_RESOLUTION_15BIT - 1;
+		clk_rate = lpg_clk_rates_hi_res[chan->clk_sel];
+	} else {
+		max = LPG_RESOLUTION_9BIT - 1;
+		clk_rate = lpg_clk_rates[chan->clk_sel];
+	}
 
-	val = div64_u64(duty * lpg_clk_rates[chan->clk_sel],
+	val = div64_u64(duty * clk_rate,
 			(u64)NSEC_PER_SEC * lpg_pre_divs[chan->pre_div_sel] * (1 << chan->pre_div_exp));
 
 	chan->pwm_value = min(val, max);
@@ -354,7 +403,7 @@ static void lpg_apply_freq(struct lpg_channel *chan)
 
 	val = chan->clk_sel;
 
-	/* Specify 9bit resolution, based on the subtype of the channel */
+	/* Specify resolution, based on the subtype of the channel */
 	switch (chan->subtype) {
 	case LPG_SUBTYPE_LPG:
 		val |= GENMASK(5, 4);
@@ -362,6 +411,9 @@ static void lpg_apply_freq(struct lpg_channel *chan)
 	case LPG_SUBTYPE_PWM:
 		val |= BIT(2);
 		break;
+	case LPG_SUBTYPE_HI_RES_PWM:
+		val |= FIELD_PREP(PWM_SIZE_HI_RES_MASK, chan->pwm_resolution_sel);
+		break;
 	case LPG_SUBTYPE_LPG_LITE:
 	default:
 		val |= BIT(4);
@@ -670,7 +722,7 @@ static int lpg_blink_set(struct lpg_led *led,
 	triled_set(lpg, triled_mask, triled_mask);
 
 	chan = led->channels[0];
-	duty = div_u64(chan->pwm_value * chan->period, LPG_RESOLUTION);
+	duty = div_u64(chan->pwm_value * chan->period, LPG_RESOLUTION_9BIT);
 	*delay_on = div_u64(duty, NSEC_PER_MSEC);
 	*delay_off = div_u64(chan->period - duty, NSEC_PER_MSEC);
 
@@ -977,6 +1029,7 @@ static int lpg_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 {
 	struct lpg *lpg = container_of(chip, struct lpg, pwm);
 	struct lpg_channel *chan = &lpg->channels[pwm->hwpwm];
+	unsigned int resolution;
 	unsigned int pre_div;
 	unsigned int refclk;
 	unsigned int val;
@@ -988,7 +1041,14 @@ static int lpg_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (ret)
 		return ret;
 
-	refclk = lpg_clk_rates[val & PWM_CLK_SELECT_MASK];
+	if (chan->subtype == LPG_SUBTYPE_HI_RES_PWM) {
+		refclk = lpg_clk_rates_hi_res[FIELD_GET(PWM_CLK_SELECT_HI_RES_MASK, val)];
+		resolution = lpg_pwm_resolution_hi_res[FIELD_GET(PWM_SIZE_HI_RES_MASK, val)];
+	} else {
+		refclk = lpg_clk_rates[FIELD_GET(PWM_CLK_SELECT_MASK, val)];
+		resolution = 9;
+	}
+
 	if (refclk) {
 		ret = regmap_read(lpg->map, chan->base + LPG_PREDIV_CLK_REG, &val);
 		if (ret)
@@ -1001,7 +1061,8 @@ static int lpg_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 		if (ret)
 			return ret;
 
-		state->period = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * LPG_RESOLUTION * pre_div * (1 << m), refclk);
+		state->period = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * (1 << resolution) *
+						 pre_div * (1 << m), refclk);
 		state->duty_cycle = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC * pwm_value * pre_div * (1 << m), refclk);
 	} else {
 		state->period = 0;
@@ -1149,7 +1210,7 @@ static int lpg_add_led(struct lpg *lpg, struct device_node *np)
 	}
 
 	cdev->default_trigger = of_get_property(np, "linux,default-trigger", NULL);
-	cdev->max_brightness = LPG_RESOLUTION - 1;
+	cdev->max_brightness = LPG_RESOLUTION_9BIT - 1;
 
 	if (!of_property_read_string(np, "default-state", &state) &&
 	    !strcmp(state, "on"))