pwm: driver for qualcomm ipq6018 pwm block

Driver for the PWM block in Qualcomm IPQ6018 line of SoCs. Based on
driver from downstream Codeaurora kernel tree. Removed support for older
(V1) variants because I have no access to that hardware.

Tested on IPQ6010 based hardware.

Signed-off-by: Baruch Siach <baruch.siach@siklu.com>

drivers/pwm/Kconfig

@@ -260,6 +260,18 @@ config PWM_INTEL_LGM
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-intel-lgm.
 
+config PWM_IPQ
+	tristate "IPQ PWM support"
+	depends on ARCH_QCOM || COMPILE_TEST
+	depends on HAVE_CLK && HAS_IOMEM
+	help
+	  Generic PWM framework driver for IPQ PWM block which supports
+	  4 pwm channels. Each of the these channels can be configured
+	  independent of each other.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-ipq.
+
 config PWM_IQS620A
 	tristate "Azoteq IQS620A PWM support"
 	depends on MFD_IQS62X || COMPILE_TEST

drivers/pwm/Makefile

@@ -22,6 +22,7 @@ obj-$(CONFIG_PWM_IMX1)		+= pwm-imx1.o
 obj-$(CONFIG_PWM_IMX27)		+= pwm-imx27.o
 obj-$(CONFIG_PWM_IMX_TPM)	+= pwm-imx-tpm.o
 obj-$(CONFIG_PWM_INTEL_LGM)	+= pwm-intel-lgm.o
+obj-$(CONFIG_PWM_IPQ)		+= pwm-ipq.o
 obj-$(CONFIG_PWM_IQS620A)	+= pwm-iqs620a.o
 obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
 obj-$(CONFIG_PWM_KEEMBAY)	+= pwm-keembay.o

drivers/pwm/pwm-ipq.c

@@ -0,0 +1,281 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*
+ * Copyright (c) 2016-2017, 2020 The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/math64.h>
+#include <linux/of_device.h>
+#include <linux/bitfield.h>
+#include <linux/units.h>
+
+/* The frequency range supported is 1 Hz to clock rate */
+#define IPQ_PWM_MAX_PERIOD_NS	((u64)NSEC_PER_SEC)
+
+/*
+ * The max value specified for each field is based on the number of bits
+ * in the pwm control register for that field
+ */
+#define IPQ_PWM_MAX_DIV		0xFFFF
+
+/*
+ * Two 32-bit registers for each PWM: REG0, and REG1.
+ * Base offset for PWM #i is at 8 * #i.
+ */
+#define IPQ_PWM_REG0			0
+#define IPQ_PWM_REG0_PWM_DIV		GENMASK(15, 0)
+#define IPQ_PWM_REG0_HI_DURATION	GENMASK(31, 16)
+
+#define IPQ_PWM_REG1			4
+#define IPQ_PWM_REG1_PRE_DIV		GENMASK(15, 0)
+/*
+ * Enable bit is set to enable output toggling in pwm device.
+ * Update bit is set to reflect the changed divider and high duration
+ * values in register.
+ */
+#define IPQ_PWM_REG1_UPDATE		BIT(30)
+#define IPQ_PWM_REG1_ENABLE		BIT(31)
+
+
+struct ipq_pwm_chip {
+	struct pwm_chip chip;
+	struct clk *clk;
+	void __iomem *mem;
+};
+
+static struct ipq_pwm_chip *ipq_pwm_from_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct ipq_pwm_chip, chip);
+}
+
+static unsigned int ipq_pwm_reg_read(struct pwm_device *pwm, unsigned int reg)
+{
+	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip);
+	unsigned int off = 8 * pwm->hwpwm + reg;
+
+	return readl(ipq_chip->mem + off);
+}
+
+static void ipq_pwm_reg_write(struct pwm_device *pwm, unsigned int reg,
+			      unsigned int val)
+{
+	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip);
+	unsigned int off = 8 * pwm->hwpwm + reg;
+
+	writel(val, ipq_chip->mem + off);
+}
+
+static void config_div_and_duty(struct pwm_device *pwm, unsigned int pre_div,
+			unsigned int pwm_div, unsigned long rate, u64 duty_ns,
+			bool enable)
+{
+	unsigned long hi_dur;
+	unsigned long val = 0;
+
+	/*
+	 * high duration = pwm duty * (pwm div + 1)
+	 * pwm duty = duty_ns / period_ns
+	 */
+	hi_dur = div64_u64(duty_ns * rate, (pre_div + 1) * NSEC_PER_SEC);
+
+	val = FIELD_PREP(IPQ_PWM_REG0_HI_DURATION, hi_dur) |
+		FIELD_PREP(IPQ_PWM_REG0_PWM_DIV, pwm_div);
+	ipq_pwm_reg_write(pwm, IPQ_PWM_REG0, val);
+
+	val = FIELD_PREP(IPQ_PWM_REG1_PRE_DIV, pre_div);
+	ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val);
+
+	/* PWM enable toggle needs a separate write to REG1 */
+	val |= IPQ_PWM_REG1_UPDATE;
+	if (enable)
+		val |= IPQ_PWM_REG1_ENABLE;
+	ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val);
+}
+
+static int ipq_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			 const struct pwm_state *state)
+{
+	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip);
+	unsigned int pre_div, pwm_div, best_pre_div, best_pwm_div;
+	unsigned long rate = clk_get_rate(ipq_chip->clk);
+	u64 period_ns, duty_ns, period_rate;
+	u64 min_diff;
+
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
+
+	if (state->period < DIV64_U64_ROUND_UP(NSEC_PER_SEC, rate))
+		return -ERANGE;
+
+	period_ns = min(state->period, IPQ_PWM_MAX_PERIOD_NS);
+	duty_ns = min(state->duty_cycle, period_ns);
+
+	/*
+	 * period_ns is 1G or less. As long as rate is less than 16 GHz,
+	 * period_rate does not overflow. Make that explicit.
+	 */
+	if (rate > 16ULL * GIGA)
+		return -EINVAL;
+	period_rate = period_ns * rate;
+	best_pre_div = IPQ_PWM_MAX_DIV;
+	best_pwm_div = IPQ_PWM_MAX_DIV;
+	/*
+	 * We don't need to consider pre_div values smaller than
+	 *
+	 *                              period_rate
+	 *  pre_div_min := ------------------------------------
+	 *                 NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)
+	 *
+	 * because pre_div = pre_div_min results in a better
+	 * approximation.
+	 */
+	pre_div = div64_u64(period_rate,
+			(u64)NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1));
+	min_diff = period_rate;
+
+	for (; pre_div <= IPQ_PWM_MAX_DIV; pre_div++) {
+		u64 remainder;
+
+		pwm_div = div64_u64_rem(period_rate,
+				(u64)NSEC_PER_SEC * (pre_div + 1), &remainder);
+		/* pwm_div is unsigned; the check below catches underflow */
+		pwm_div--;
+
+		/*
+		 * Swapping values for pre_div and pwm_div produces the same
+		 * period length. So we can skip all settings with pre_div >
+		 * pwm_div which results in bigger constraints for selecting
+		 * the duty_cycle than with the two values swapped.
+		 */
+		if (pre_div > pwm_div)
+			break;
+
+		/*
+		 * Make sure we can do 100% duty cycle where
+		 * hi_dur == pwm_div + 1
+		 */
+		if (pwm_div > IPQ_PWM_MAX_DIV - 1)
+			continue;
+
+		if (remainder < min_diff) {
+			best_pre_div = pre_div;
+			best_pwm_div = pwm_div;
+			min_diff = remainder;
+
+			if (min_diff == 0) /* bingo */
+				break;
+		}
+	}
+
+	/* config divider values for the closest possible frequency */
+	config_div_and_duty(pwm, best_pre_div, best_pwm_div,
+			    rate, duty_ns, state->enabled);
+
+	return 0;
+}
+
+static void ipq_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			      struct pwm_state *state)
+{
+	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip);
+	unsigned long rate = clk_get_rate(ipq_chip->clk);
+	unsigned int pre_div, pwm_div, hi_dur;
+	u64 effective_div, hi_div;
+	u32 reg0, reg1;
+
+	reg0 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG0);
+	reg1 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG1);
+
+	state->polarity = PWM_POLARITY_NORMAL;
+	state->enabled = reg1 & IPQ_PWM_REG1_ENABLE;
+
+	pwm_div = FIELD_GET(IPQ_PWM_REG0_PWM_DIV, reg0);
+	hi_dur = FIELD_GET(IPQ_PWM_REG0_HI_DURATION, reg0);
+	pre_div = FIELD_GET(IPQ_PWM_REG1_PRE_DIV, reg1);
+
+	/* No overflow here, both pre_div and pwm_div <= 0xffff */
+	effective_div = (u64)(pre_div + 1) * (pwm_div + 1);
+	state->period = DIV64_U64_ROUND_UP(effective_div * NSEC_PER_SEC, rate);
+
+	hi_div = hi_dur * (pre_div + 1);
+	state->duty_cycle = DIV64_U64_ROUND_UP(hi_div * NSEC_PER_SEC, rate);
+}
+
+static const struct pwm_ops ipq_pwm_ops = {
+	.apply = ipq_pwm_apply,
+	.get_state = ipq_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int ipq_pwm_probe(struct platform_device *pdev)
+{
+	struct ipq_pwm_chip *pwm;
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	pwm = devm_kzalloc(dev, sizeof(*pwm), GFP_KERNEL);
+	if (!pwm)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, pwm);
+
+	pwm->mem = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pwm->mem))
+		return dev_err_probe(dev, PTR_ERR(pwm->mem),
+				"regs map failed");
+
+	pwm->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(pwm->clk))
+		return dev_err_probe(dev, PTR_ERR(pwm->clk),
+				"failed to get clock");
+
+	ret = clk_prepare_enable(pwm->clk);
+	if (ret)
+		return dev_err_probe(dev, ret, "clock enable failed");
+
+	pwm->chip.dev = dev;
+	pwm->chip.ops = &ipq_pwm_ops;
+	pwm->chip.npwm = 4;
+
+	ret = pwmchip_add(&pwm->chip);
+	if (ret < 0) {
+		dev_err_probe(dev, ret, "pwmchip_add() failed\n");
+		clk_disable_unprepare(pwm->clk);
+	}
+
+	return ret;
+}
+
+static int ipq_pwm_remove(struct platform_device *pdev)
+{
+	struct ipq_pwm_chip *pwm = platform_get_drvdata(pdev);
+
+	pwmchip_remove(&pwm->chip);
+	clk_disable_unprepare(pwm->clk);
+
+	return 0;
+}
+
+static const struct of_device_id pwm_ipq_dt_match[] = {
+	{ .compatible = "qcom,ipq6018-pwm", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, pwm_ipq_dt_match);
+
+static struct platform_driver ipq_pwm_driver = {
+	.driver = {
+		.name = "ipq-pwm",
+		.of_match_table = pwm_ipq_dt_match,
+	},
+	.probe = ipq_pwm_probe,
+	.remove = ipq_pwm_remove,
+};
+
+module_platform_driver(ipq_pwm_driver);
+
+MODULE_LICENSE("Dual BSD/GPL");