[PATCH v12 0/2] PWM support for HiFive Unleashed

[PATCH v12 0/2] PWM support for HiFive Unleashed

[Yash Shah]

This patch series adds a PWM driver and DT documentation
for HiFive Unleashed board. The patches are mostly based on
Wesley's patch.

This patchset is based on Linux v5.1 and tested on HiFive Unleashed board
with additional board related patches needed for testing can be found at
dev/yashs/pwm branch of:
https://github.com/yashshah7/riscv-linux.git

v12
- Rebased onto Mainline v5.1

v11
- Change naming convention for pwm_device and pwm_sifive_ddata pointers
- Assign of_pwm_xlate_with_flag() to of_xlate func ptr since this driver
  use three pwm-cells (Issue reported by Andreas Schwab <schwab@suse.de>
- Other minor fixes

v10
- Use DIV_ROUND_CLOSEST_ULL instead of div_u64_round
- Change 'num' defination to u64 bit (in pwm_sifive_apply).
- Remove the usage of pwm_get_state()

v9
- Use appropriate bitfield macros
- Add approx_period in pwm_sifive_ddata struct and related changes
- Correct the eqn for calculation of frac (in pwm_sifive_apply)
- Other minor fixes

v8
- Typo corrections
- Remove active_user and related code
- Do not clear PWM_SIFIVE_PWMCFG_EN_ALWAYS
- Other minor fixes

v7
- Modify description of compatible property in DT documentation
- Use mutex locks at appropriate places
- Fix all bad line breaks
- Allow enabling/disabling PWM only when the user is the only active user
- Remove Deglitch logic
- Other minor fixes

v6
- Remove the global property 'sifive,period-ns'
- Implement free and request callbacks to maintain user counts.
- Add user_count member to struct pwm_sifive_ddata
- Allow period change only if user_count is one
- Add pwm_sifive_enable function to enable/disable PWM
- Change calculation logic of frac (in pwm_sifive_apply)
- Remove state correction
- Remove pwm_sifive_xlate function
- Clock to be enabled only when PWM is enabled
- Other minor fixes

v5
- Correct the order of compatible string properties
- PWM state correction to be done always
- Other minor fixes based upon feedback on v4

v4
- Rename macros with appropriate names
- Remove unused macros
- Rename struct sifive_pwm_device to struct pwm_sifive_ddata
- Rename function prefix as per driver name
- Other minor fixes based upon feedback on v3

v3
- Add a link to the reference manaul
- Use appropriate apis for division operation
- Add check for polarity
- Enable clk before calling clk_get_rate
- Other minor fixes based upon feedback on v2

V2 changed from V1:
- Remove inclusion of dt-bindings/pwm/pwm.h
- Remove artificial alignments
- Replace ioread32/iowrite32 with readl/writel
- Remove camelcase
- Change dev_info to dev_dbg for unnecessary log
- Correct typo in driver name
- Remove use of of_match_ptr macro
- Update the DT compatible strings and Add reference to a common
  versioning document

Yash Shah (2):
  pwm: sifive: Add DT documentation for SiFive PWM Controller
  pwm: sifive: Add a driver for SiFive SoC PWM

 .../devicetree/bindings/pwm/pwm-sifive.txt         |  33 ++
 drivers/pwm/Kconfig                                |  11 +
 drivers/pwm/Makefile                               |   1 +
 drivers/pwm/pwm-sifive.c                           | 338 +++++++++++++++++++++
 4 files changed, 383 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/pwm-sifive.txt
 create mode 100644 drivers/pwm/pwm-sifive.c

-- 
1.9.1

[PATCH v12 1/2] pwm: sifive: Add DT documentation for SiFive PWM Controller

[Yash Shah]

DT documentation for PWM controller added.

Signed-off-by: Wesley W. Terpstra <wesley@sifive.com>
[Atish: Compatible string update]
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Yash Shah <yash.shah@sifive.com>
Reviewed-by: Rob Herring <robh@kernel.org>
---
 .../devicetree/bindings/pwm/pwm-sifive.txt         | 33 ++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/pwm-sifive.txt

diff --git a/Documentation/devicetree/bindings/pwm/pwm-sifive.txt b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
new file mode 100644
index 0000000..36447e3
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm-sifive.txt
@@ -0,0 +1,33 @@
+SiFive PWM controller
+
+Unlike most other PWM controllers, the SiFive PWM controller currently only
+supports one period for all channels in the PWM. All PWMs need to run at
+the same period. The period also has significant restrictions on the values
+it can achieve, which the driver rounds to the nearest achievable period.
+PWM RTL that corresponds to the IP block version numbers can be found
+here:
+
+https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/pwm
+
+Required properties:
+- compatible: Should be "sifive,<chip>-pwm" and "sifive,pwm<version>".
+  Supported compatible strings are: "sifive,fu540-c000-pwm" for the SiFive
+  PWM v0 as integrated onto the SiFive FU540 chip, and "sifive,pwm0" for the
+  SiFive PWM v0 IP block with no chip integration tweaks.
+  Please refer to sifive-blocks-ip-versioning.txt for details.
+- reg: physical base address and length of the controller's registers
+- clocks: Should contain a clock identifier for the PWM's parent clock.
+- #pwm-cells: Should be 3. See pwm.txt in this directory
+  for a description of the cell format.
+- interrupts: one interrupt per PWM channel
+
+Examples:
+
+pwm:  pwm@10020000 {
+	compatible = "sifive,fu540-c000-pwm", "sifive,pwm0";
+	reg = <0x0 0x10020000 0x0 0x1000>;
+	clocks = <&tlclk>;
+	interrupt-parent = <&plic>;
+	interrupts = <42 43 44 45>;
+	#pwm-cells = <3>;
+};
-- 
1.9.1

[PATCH v12 2/2] pwm: sifive: Add a driver for SiFive SoC PWM

[Yash Shah]

Adds a PWM driver for PWM chip present in SiFive's HiFive Unleashed SoC.

Signed-off-by: Wesley W. Terpstra <wesley@sifive.com>
[Atish: Various fixes and code cleanup]
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Yash Shah <yash.shah@sifive.com>
---
 drivers/pwm/Kconfig      |  11 ++
 drivers/pwm/Makefile     |   1 +
 drivers/pwm/pwm-sifive.c | 338 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 350 insertions(+)
 create mode 100644 drivers/pwm/pwm-sifive.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 54f8238..95c1181 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -389,6 +389,17 @@ config PWM_SAMSUNG
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-samsung.
 
+config PWM_SIFIVE
+	tristate "SiFive PWM support"
+	depends on OF
+	depends on COMMON_CLK
+	depends on RISCV || COMPILE_TEST
+	help
+	  Generic PWM framework driver for SiFive SoCs.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-sifive.
+
 config PWM_SPEAR
 	tristate "STMicroelectronics SPEAr PWM support"
 	depends on PLAT_SPEAR
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 448825e..0da3e99 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_PWM_RCAR)		+= pwm-rcar.o
 obj-$(CONFIG_PWM_RENESAS_TPU)	+= pwm-renesas-tpu.o
 obj-$(CONFIG_PWM_ROCKCHIP)	+= pwm-rockchip.o
 obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o
+obj-$(CONFIG_PWM_SIFIVE)	+= pwm-sifive.o
 obj-$(CONFIG_PWM_SPEAR)		+= pwm-spear.o
 obj-$(CONFIG_PWM_STI)		+= pwm-sti.o
 obj-$(CONFIG_PWM_STM32)		+= pwm-stm32.o
diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
new file mode 100644
index 0000000..1921e6ea
--- /dev/null
+++ b/drivers/pwm/pwm-sifive.c
@@ -0,0 +1,338 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2017-2018 SiFive
+ * For SiFive's PWM IP block documentation please refer Chapter 14 of
+ * Reference Manual : https://static.dev.sifive.com/FU540-C000-v1.0.pdf
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we cannot prevent in
+ *   software that the output might produce a period with mixed
+ *   settings (new period length and old duty cycle).
+ * - The hardware cannot generate a 100% duty cycle.
+ * - The hardware generates only inverted output.
+ */
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+#include <linux/bitfield.h>
+
+/* Register offsets */
+#define PWM_SIFIVE_PWMCFG		0x0
+#define PWM_SIFIVE_PWMCOUNT		0x8
+#define PWM_SIFIVE_PWMS			0x10
+#define PWM_SIFIVE_PWMCMP0		0x20
+
+/* PWMCFG fields */
+#define PWM_SIFIVE_PWMCFG_SCALE		GENMASK(3, 0)
+#define PWM_SIFIVE_PWMCFG_STICKY	BIT(8)
+#define PWM_SIFIVE_PWMCFG_ZERO_CMP	BIT(9)
+#define PWM_SIFIVE_PWMCFG_DEGLITCH	BIT(10)
+#define PWM_SIFIVE_PWMCFG_EN_ALWAYS	BIT(12)
+#define PWM_SIFIVE_PWMCFG_EN_ONCE	BIT(13)
+#define PWM_SIFIVE_PWMCFG_CENTER	BIT(16)
+#define PWM_SIFIVE_PWMCFG_GANG		BIT(24)
+#define PWM_SIFIVE_PWMCFG_IP		BIT(28)
+
+/* PWM_SIFIVE_SIZE_PWMCMP is used to calculate offset for pwmcmpX registers */
+#define PWM_SIFIVE_SIZE_PWMCMP		4
+#define PWM_SIFIVE_CMPWIDTH		16
+#define PWM_SIFIVE_DEFAULT_PERIOD	10000000
+
+struct pwm_sifive_ddata {
+	struct pwm_chip	chip;
+	struct mutex lock; /* lock to protect user_count */
+	struct notifier_block notifier;
+	struct clk *clk;
+	void __iomem *regs;
+	unsigned int real_period;
+	unsigned int approx_period;
+	int user_count;
+};
+
+static inline
+struct pwm_sifive_ddata *pwm_sifive_chip_to_ddata(struct pwm_chip *c)
+{
+	return container_of(c, struct pwm_sifive_ddata, chip);
+}
+
+static int pwm_sifive_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+
+	mutex_lock(&ddata->lock);
+	ddata->user_count++;
+	mutex_unlock(&ddata->lock);
+
+	return 0;
+}
+
+static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+
+	mutex_lock(&ddata->lock);
+	ddata->user_count--;
+	mutex_unlock(&ddata->lock);
+}
+
+static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
+				    unsigned long rate)
+{
+	unsigned long long num;
+	unsigned long scale_pow;
+	int scale;
+	u32 val;
+	/*
+	 * The PWM unit is used with pwmzerocmp=0, so the only way to modify the
+	 * period length is using pwmscale which provides the number of bits the
+	 * counter is shifted before being feed to the comparators. A period
+	 * lasts (1 << (PWM_SIFIVE_CMPWIDTH + pwmscale)) clock ticks.
+	 * (1 << (PWM_SIFIVE_CMPWIDTH + scale)) * 10^9/rate = period
+	 */
+	scale_pow = div64_ul(ddata->approx_period * (u64)rate, NSEC_PER_SEC);
+	scale = clamp(ilog2(scale_pow) - PWM_SIFIVE_CMPWIDTH, 0, 0xf);
+
+	val = PWM_SIFIVE_PWMCFG_EN_ALWAYS |
+	      FIELD_PREP(PWM_SIFIVE_PWMCFG_SCALE, scale);
+	writel(val, ddata->regs + PWM_SIFIVE_PWMCFG);
+
+	/* As scale <= 15 the shift operation cannot overflow. */
+	num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
+	ddata->real_period = div64_ul(num, rate);
+	dev_dbg(ddata->chip.dev,
+		"New real_period = %u ns\n", ddata->real_period);
+}
+
+static void pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+	u32 duty, val;
+
+	duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP0 +
+		     pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
+
+	state->enabled = duty > 0;
+
+	val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
+	if (!(val & PWM_SIFIVE_PWMCFG_EN_ALWAYS))
+		state->enabled = false;
+
+	state->period = ddata->real_period;
+	state->duty_cycle =
+		(u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
+	state->polarity = PWM_POLARITY_INVERSED;
+}
+
+static int pwm_sifive_enable(struct pwm_chip *chip, bool enable)
+{
+	struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+	int ret;
+
+	if (enable) {
+		ret = clk_enable(ddata->clk);
+		if (ret) {
+			dev_err(ddata->chip.dev, "Enable clk failed\n");
+			return ret;
+		}
+	}
+
+	if (!enable)
+		clk_disable(ddata->clk);
+
+	return 0;
+}
+
+static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    struct pwm_state *state)
+{
+	struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+	struct pwm_state cur_state;
+	unsigned int duty_cycle;
+	unsigned long long num;
+	bool enabled;
+	int ret = 0;
+	u32 frac;
+
+	if (state->polarity != PWM_POLARITY_INVERSED)
+		return -EINVAL;
+
+	ret = clk_enable(ddata->clk);
+	if (ret) {
+		dev_err(ddata->chip.dev, "Enable clk failed\n");
+		return ret;
+	}
+
+	mutex_lock(&ddata->lock);
+	cur_state = pwm->state;
+	enabled = cur_state.enabled;
+
+	duty_cycle = state->duty_cycle;
+	if (!state->enabled)
+		duty_cycle = 0;
+
+	/*
+	 * The problem of output producing mixed setting as mentioned at top,
+	 * occurs here. To minimize the window for this problem, we are
+	 * calculating the register values first and then writing them
+	 * consecutively
+	 */
+	num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
+	frac = DIV_ROUND_CLOSEST_ULL(num, state->period);
+	/* The hardware cannot generate a 100% duty cycle */
+	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
+
+	if (state->period != ddata->approx_period) {
+		if (ddata->user_count != 1) {
+			ret = -EBUSY;
+			goto exit;
+		}
+		ddata->approx_period = state->period;
+		pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
+	}
+
+	writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP0 +
+	       pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
+
+	if (state->enabled != enabled)
+		pwm_sifive_enable(chip, state->enabled);
+
+exit:
+	clk_disable(ddata->clk);
+	mutex_unlock(&ddata->lock);
+	return ret;
+}
+
+static const struct pwm_ops pwm_sifive_ops = {
+	.request = pwm_sifive_request,
+	.free = pwm_sifive_free,
+	.get_state = pwm_sifive_get_state,
+	.apply = pwm_sifive_apply,
+	.owner = THIS_MODULE,
+};
+
+static int pwm_sifive_clock_notifier(struct notifier_block *nb,
+				     unsigned long event, void *data)
+{
+	struct clk_notifier_data *ndata = data;
+	struct pwm_sifive_ddata *ddata =
+		container_of(nb, struct pwm_sifive_ddata, notifier);
+
+	if (event == POST_RATE_CHANGE)
+		pwm_sifive_update_clock(ddata, ndata->new_rate);
+
+	return NOTIFY_OK;
+}
+
+static int pwm_sifive_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pwm_sifive_ddata *ddata;
+	struct pwm_chip *chip;
+	struct resource *res;
+	int ret;
+
+	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	mutex_init(&ddata->lock);
+	chip = &ddata->chip;
+	chip->dev = dev;
+	chip->ops = &pwm_sifive_ops;
+	chip->of_xlate = of_pwm_xlate_with_flags;
+	chip->of_pwm_n_cells = 3;
+	chip->base = -1;
+	chip->npwm = 4;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	ddata->regs = devm_ioremap_resource(dev, res);
+	if (IS_ERR(ddata->regs)) {
+		dev_err(dev, "Unable to map IO resources\n");
+		return PTR_ERR(ddata->regs);
+	}
+
+	ddata->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(ddata->clk)) {
+		if (PTR_ERR(ddata->clk) != -EPROBE_DEFER)
+			dev_err(dev, "Unable to find controller clock\n");
+		return PTR_ERR(ddata->clk);
+	}
+
+	ret = clk_prepare_enable(ddata->clk);
+	if (ret) {
+		dev_err(dev, "failed to enable clock for pwm: %d\n", ret);
+		return ret;
+	}
+
+	/* Watch for changes to underlying clock frequency */
+	ddata->notifier.notifier_call = pwm_sifive_clock_notifier;
+	ret = clk_notifier_register(ddata->clk, &ddata->notifier);
+	if (ret) {
+		dev_err(dev, "failed to register clock notifier: %d\n", ret);
+		goto disable_clk;
+	}
+
+	ret = pwmchip_add(chip);
+	if (ret < 0) {
+		dev_err(dev, "cannot register PWM: %d\n", ret);
+		goto unregister_clk;
+	}
+
+	platform_set_drvdata(pdev, ddata);
+	dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
+
+	return 0;
+
+unregister_clk:
+	clk_notifier_unregister(ddata->clk, &ddata->notifier);
+disable_clk:
+	clk_disable_unprepare(ddata->clk);
+
+	return ret;
+}
+
+static int pwm_sifive_remove(struct platform_device *dev)
+{
+	struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev);
+	bool is_enabled = false;
+	struct pwm_device *pwm;
+	int ret, ch;
+
+	ret = pwmchip_remove(&ddata->chip);
+	clk_notifier_unregister(ddata->clk, &ddata->notifier);
+
+	for (ch = 0; ch < ddata->chip.npwm; ch++) {
+		pwm = &ddata->chip.pwms[ch];
+		if (pwm->state.enabled) {
+			is_enabled = true;
+			break;
+		}
+	}
+	if (is_enabled)
+		clk_disable(ddata->clk);
+	clk_disable_unprepare(ddata->clk);
+	return ret;
+}
+
+static const struct of_device_id pwm_sifive_of_match[] = {
+	{ .compatible = "sifive,pwm0" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, pwm_sifive_of_match);
+
+static struct platform_driver pwm_sifive_driver = {
+	.probe = pwm_sifive_probe,
+	.remove = pwm_sifive_remove,
+	.driver = {
+		.name = "pwm-sifive",
+		.of_match_table = pwm_sifive_of_match,
+	},
+};
+module_platform_driver(pwm_sifive_driver);
+
+MODULE_DESCRIPTION("SiFive PWM driver");
+MODULE_LICENSE("GPL v2");
-- 
1.9.1