[RFC PATCH] pwm: add pwm-atmel from Linux kernel 4.14

[Sam Ravnborg <sam@ravnborg.org>]

Following patch is more or less untested.

It is posted to get feedback if this is the right way to
implement support for pwms in at91sam9263 & friends.

In the kernel there is also a file named pwm-atmel-tcb.
I dunno which is the better starting point.

The patch will recognize pwm0 on the at91sam9263ek board
(if status = "okay") so it has seen minimal testing.
But I have yet to utilize any of the pwm's.

While working with this I get the impression that the core
should know about pwm channels and device_d pointer
should be part of the core data.
But I was not prepared to make anything but local changes
in this round.

Feedback appreciated!

	Sam


From 4868c3d0687bfc3b870c295fe33b021a239c7a6a Mon Sep 17 00:00:00 2001
From: Sam Ravnborg <sam@ravnborg.org>
Date: Sat, 30 Dec 2017 08:28:33 +0100
Subject: [PATCH 1/1] pwm: add pwm-atmel from Linux kernel 4.14

This add the pwm-atmel.c file from kernel 4.14,
modified for barebox use.

The code is modelled over pwm-mxs.

pwm-atmel is required to support PWM's used on a board
with AT91SAM9263 - controlling backlight and contrast.

---
 drivers/pwm/Kconfig     |   6 +
 drivers/pwm/Makefile    |   1 +
 drivers/pwm/pwm-atmel.c | 289 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 296 insertions(+)
 create mode 100644 drivers/pwm/pwm-atmel.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 97c3deff1..5242c35e9 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -16,6 +16,12 @@ config PWM_PXA
 	  This enables PWM support for Intel/Marvell PXA chips, such
 	  as the PXA25x, PXA27x.
 
+config PWM_ATMEL
+	bool "Atmel PWM Support"
+	depends on ARCH_AT91
+	help
+	  This enables PWM support for Ateml AT91 SoCs
+
 config PWM_IMX
 	bool "i.MX PWM Support"
 	depends on ARCH_IMX
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 46865a24e..d2ae19b9a 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -1,4 +1,5 @@
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_PXA)		+= pxa_pwm.o
+obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o
 obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
new file mode 100644
index 000000000..7fa394934
--- /dev/null
+++ b/drivers/pwm/pwm-atmel.c
@@ -0,0 +1,289 @@
+/*
+ * Driver for Atmel Pulse Width Modulation Controller
+ *
+ * Copyright (C) 2013 Atmel Corporation
+ *		 Bo Shen <voice.shen@atmel.com>
+ * Copyright (C) 2018 Sam Ravnborg <sam@ravnborg.org>
+ *
+ * Licensed under GPLv2.
+ */
+
+#include <of_device.h>
+#include <common.h>
+#include <driver.h>
+#include <module.h>
+#include <printk.h>
+#include <stdio.h>
+#include <init.h>
+#include <pwm.h>
+#include <io.h>
+#include <of.h>
+
+#include <asm-generic/div64.h>
+
+#include <linux/time.h>
+#include <linux/clk.h>
+
+
+#define PWM_CHANNELS		4
+
+/* The following is global registers for PWM controller */
+#define PWM_ENA			0x04
+#define PWM_DIS			0x08
+#define PWM_SR			0x0C
+#define PWM_ISR			0x1C
+/* Bit field in SR */
+#define PWM_SR_ALL_CH_ON	0x0F
+
+/* The following register is PWM channel related registers */
+#define PWM_CH_REG_OFFSET	0x200
+#define PWM_CH_REG_SIZE		0x20
+
+#define PWM_CMR			0x0
+/* Bit field in CMR */
+#define PWM_CMR_CPOL		(1 << 9)
+#define PWM_CMR_UPD_CDTY	(1 << 10)
+#define PWM_CMR_CPRE_MSK	0xF
+
+/* The following registers for PWM v1 */
+#define PWMV1_CDTY		0x04
+#define PWMV1_CPRD		0x08
+#define PWMV1_CUPD		0x10
+
+/* The following registers for PWM v2 */
+#define PWMV2_CDTY		0x04
+#define PWMV2_CDTYUPD		0x08
+#define PWMV2_CPRD		0x0C
+#define PWMV2_CPRDUPD		0x10
+
+/*
+ * Max value for duty and period
+ *
+ * Although the duty and period register is 32 bit,
+ * however only the LSB 16 bits are significant.
+ */
+#define PWM_MAX_DTY		0xFFFF
+#define PWM_MAX_PRD		0xFFFF
+#define PRD_MAX_PRES		10
+
+struct atmel_pwm_registers {
+	u8 period;
+	u8 period_upd;
+	u8 duty;
+	u8 duty_upd;
+};
+
+struct atmel_pwm;
+
+struct atmel_pwm_chip {
+	struct pwm_chip chip;
+	struct atmel_pwm *atmel;
+};
+
+struct atmel_pwm {
+	struct atmel_pwm_chip atmel_pwm_chip[PWM_CHANNELS];
+	const struct atmel_pwm_registers *regs;
+	struct clk *clk;
+	void __iomem *base;
+	struct device_d *dev;
+};
+
+static inline struct atmel_pwm_chip *to_atmel_pwm_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct atmel_pwm_chip, chip);
+}
+
+static inline void atmel_pwm_writel(struct atmel_pwm_chip *chip,
+				    unsigned long offset, unsigned long val)
+{
+	writel(val, chip->atmel->base + offset);
+}
+
+static inline u32 atmel_pwm_ch_readl(struct atmel_pwm_chip *chip,
+				     unsigned int ch, unsigned long offset)
+{
+	unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
+
+	return readl(chip->atmel->base + base + offset);
+}
+
+static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
+				       unsigned int ch, unsigned long offset,
+				       unsigned long val)
+{
+	unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
+
+	writel(val, chip->atmel->base + base + offset);
+}
+
+static int atmel_pwm_calculate_cprd_and_pres(struct atmel_pwm_chip *atmel_pwm,
+					     int period,
+					     unsigned long *cprd, u32 *pres)
+{
+	unsigned long long cycles = period;
+	/* Calculate the period cycles and prescale value */
+	cycles *= clk_get_rate(atmel_pwm->atmel->clk);
+	do_div(cycles, NSEC_PER_SEC);
+
+	for (*pres = 0; cycles > PWM_MAX_PRD; cycles >>= 1)
+		(*pres)++;
+
+	if (*pres > PRD_MAX_PRES) {
+		dev_err(atmel_pwm->atmel->dev, "pres exceeds the maximum value\n");
+		return -EINVAL;
+	}
+
+	*cprd = cycles;
+
+	return 0;
+}
+
+static void atmel_pwm_calculate_cdty(int duty, int period,
+				     unsigned long cprd, unsigned long *cdty)
+{
+	unsigned long long cycles = duty;
+
+	cycles *= cprd;
+	do_div(cycles, period);
+	*cdty = cprd - cycles;
+}
+
+static void atmel_pwm_set_cprd_cdty(struct atmel_pwm_chip *atmel_pwm, int ch,
+				    unsigned long cprd, unsigned long cdty)
+{
+	const struct atmel_pwm_registers *regs = atmel_pwm->atmel->regs;
+
+	atmel_pwm_ch_writel(atmel_pwm, ch, regs->duty, cdty);
+	atmel_pwm_ch_writel(atmel_pwm, ch, regs->period, cprd);
+}
+
+static int atmel_pwm_config(struct pwm_chip *chip, int duty_ns, int period_ns)
+{
+	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
+	unsigned long cprd, cdty;
+	u32 pres, val;
+	int ret;
+	int ch;
+
+	ch = atmel_pwm->chip.id;
+	ret = atmel_pwm_calculate_cprd_and_pres(atmel_pwm, period_ns, &cprd, &pres);
+	if (ret)
+		return ret;
+
+	atmel_pwm_calculate_cdty(duty_ns, period_ns, cprd, &cdty);
+
+	/* It is necessary to preserve CPOL, inside CMR */
+	val = atmel_pwm_ch_readl(atmel_pwm, ch, PWM_CMR);
+	val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK);
+	/* Assuming normal polarity */
+	val &= ~PWM_CMR_CPOL;
+
+	atmel_pwm_ch_writel(atmel_pwm, ch, PWM_CMR, val);
+	atmel_pwm_set_cprd_cdty(atmel_pwm, ch, cprd, cdty);
+
+	return 0;
+}
+
+static int atmel_pwm_enable(struct pwm_chip *chip)
+{
+	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
+
+	atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << atmel_pwm->chip.id);
+	return 0;
+}
+
+static void atmel_pwm_disable(struct pwm_chip *chip)
+{
+	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
+
+	atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << atmel_pwm->chip.id);
+}
+
+static struct pwm_ops atmel_pwm_ops = {
+	.config = atmel_pwm_config,
+	.enable = atmel_pwm_enable,
+	.disable = atmel_pwm_disable,
+};
+
+static const struct atmel_pwm_registers atmel_pwm_regs_v1 = {
+	.period		= PWMV1_CPRD,
+	.period_upd	= PWMV1_CUPD,
+	.duty		= PWMV1_CDTY,
+	.duty_upd	= PWMV1_CUPD,
+};
+
+static const struct atmel_pwm_registers atmel_pwm_regs_v2 = {
+	.period		= PWMV2_CPRD,
+	.period_upd	= PWMV2_CPRDUPD,
+	.duty		= PWMV2_CDTY,
+	.duty_upd	= PWMV2_CDTYUPD,
+};
+
+static const struct of_device_id atmel_pwm_dt_ids[] = {
+	{
+		.compatible = "atmel,at91sam9rl-pwm",
+		.data = &atmel_pwm_regs_v1,
+	}, {
+		.compatible = "atmel,sama5d3-pwm",
+		.data = &atmel_pwm_regs_v2,
+	}, {
+		.compatible = "atmel,sama5d2-pwm",
+		.data = &atmel_pwm_regs_v2,
+	}, {
+		/* sentinel */
+	},
+};
+
+static int atmel_pwm_probe(struct device_d *dev)
+{
+	const struct atmel_pwm_registers *regs;
+	struct atmel_pwm *atmel_pwm;
+	struct resource *res;
+	int ret;
+	int i;
+
+	ret = dev_get_drvdata(dev, (const void **)&regs);
+	if (ret)
+		return ret;
+
+	atmel_pwm = xzalloc(sizeof(*atmel_pwm));
+	atmel_pwm->regs = regs;
+	atmel_pwm->dev = dev;
+	atmel_pwm->clk = clk_get(dev, "pwm_clk");
+	if (IS_ERR(atmel_pwm->clk))
+		return PTR_ERR(atmel_pwm->clk);
+
+	res = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(res))
+		return PTR_ERR(res);
+
+	atmel_pwm->base = IOMEM(res);
+
+	for (i = 0; i < PWM_CHANNELS; i++) {
+		struct atmel_pwm_chip *chip = &atmel_pwm->atmel_pwm_chip[i];
+		chip->chip.ops = &atmel_pwm_ops;
+		chip->chip.devname = basprintf("pwm%d", i);
+		chip->chip.id = i;
+		chip->atmel = atmel_pwm;
+
+		ret = pwmchip_add(&chip->chip, dev);
+		if (ret < 0) {
+			dev_err(dev, "failed to add pwm chip[%d] %d\n", i, ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static struct driver_d atmel_pwm_driver = {
+	.name		= "atmel-pwm",
+	.of_compatible	= atmel_pwm_dt_ids,
+	.probe		= atmel_pwm_probe,
+};
+
+coredevice_platform_driver(atmel_pwm_driver);
+
+MODULE_AUTHOR("Bo Shen <voice.shen@atmel.com>");
+MODULE_DESCRIPTION("Atmel PWM driver");
+MODULE_LICENSE("GPL v2");
-- 
2.12.0


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