pwm: Add DesignWare PWM Controller Driver

Introduce driver for Synopsys DesignWare PWM Controller used on Intel
Elkhart Lake.

Initial implementation is done by Felipe Balbi while he was working at
Intel with later changes from Raymond Tan and me.
Co-developed-by: Felipe Balbi (Intel) <balbi@kernel.org>
Signed-off-by: Felipe Balbi (Intel) <balbi@kernel.org>
Co-developed-by: Raymond Tan <raymond.tan@intel.com>
Signed-off-by: Raymond Tan <raymond.tan@intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/Kconfig

@@ -161,6 +161,15 @@ config PWM_CROS_EC
 	  PWM driver for exposing a PWM attached to the ChromeOS Embedded
 	  Controller.
 
+config PWM_DWC
+	tristate "DesignWare PWM Controller"
+	depends on PCI
+	help
+	  PWM driver for Synopsys DWC PWM Controller attached to a PCI bus.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-dwc.
+
 config PWM_EP93XX
 	tristate "Cirrus Logic EP93xx PWM support"
 	depends on ARCH_EP93XX || COMPILE_TEST

drivers/pwm/Makefile

@@ -13,6 +13,7 @@ obj-$(CONFIG_PWM_BRCMSTB)	+= pwm-brcmstb.o
 obj-$(CONFIG_PWM_CLPS711X)	+= pwm-clps711x.o
 obj-$(CONFIG_PWM_CRC)		+= pwm-crc.o
 obj-$(CONFIG_PWM_CROS_EC)	+= pwm-cros-ec.o
+obj-$(CONFIG_PWM_DWC)		+= pwm-dwc.o
 obj-$(CONFIG_PWM_EP93XX)	+= pwm-ep93xx.o
 obj-$(CONFIG_PWM_FSL_FTM)	+= pwm-fsl-ftm.o
 obj-$(CONFIG_PWM_HIBVT)		+= pwm-hibvt.o

drivers/pwm/pwm-dwc.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DesignWare PWM Controller driver
+ *
+ * Copyright (C) 2018-2020 Intel Corporation
+ *
+ * Author: Felipe Balbi (Intel)
+ * Author: Jarkko Nikula <jarkko.nikula@linux.intel.com>
+ * Author: Raymond Tan <raymond.tan@intel.com>
+ *
+ * Limitations:
+ * - The hardware cannot generate a 0 % or 100 % duty cycle. Both high and low
+ *   periods are one or more input clock periods long.
+ */
+
+#include <linux/bitops.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/pm_runtime.h>
+#include <linux/pwm.h>
+
+#define DWC_TIM_LD_CNT(n)	((n) * 0x14)
+#define DWC_TIM_LD_CNT2(n)	(((n) * 4) + 0xb0)
+#define DWC_TIM_CUR_VAL(n)	(((n) * 0x14) + 0x04)
+#define DWC_TIM_CTRL(n)		(((n) * 0x14) + 0x08)
+#define DWC_TIM_EOI(n)		(((n) * 0x14) + 0x0c)
+#define DWC_TIM_INT_STS(n)	(((n) * 0x14) + 0x10)
+
+#define DWC_TIMERS_INT_STS	0xa0
+#define DWC_TIMERS_EOI		0xa4
+#define DWC_TIMERS_RAW_INT_STS	0xa8
+#define DWC_TIMERS_COMP_VERSION	0xac
+
+#define DWC_TIMERS_TOTAL	8
+#define DWC_CLK_PERIOD_NS	10
+
+/* Timer Control Register */
+#define DWC_TIM_CTRL_EN		BIT(0)
+#define DWC_TIM_CTRL_MODE	BIT(1)
+#define DWC_TIM_CTRL_MODE_FREE	(0 << 1)
+#define DWC_TIM_CTRL_MODE_USER	(1 << 1)
+#define DWC_TIM_CTRL_INT_MASK	BIT(2)
+#define DWC_TIM_CTRL_PWM	BIT(3)
+
+struct dwc_pwm_ctx {
+	u32 cnt;
+	u32 cnt2;
+	u32 ctrl;
+};
+
+struct dwc_pwm {
+	struct pwm_chip chip;
+	void __iomem *base;
+	struct dwc_pwm_ctx ctx[DWC_TIMERS_TOTAL];
+};
+#define to_dwc_pwm(p)	(container_of((p), struct dwc_pwm, chip))
+
+static inline u32 dwc_pwm_readl(struct dwc_pwm *dwc, u32 offset)
+{
+	return readl(dwc->base + offset);
+}
+
+static inline void dwc_pwm_writel(struct dwc_pwm *dwc, u32 value, u32 offset)
+{
+	writel(value, dwc->base + offset);
+}
+
+static void __dwc_pwm_set_enable(struct dwc_pwm *dwc, int pwm, int enabled)
+{
+	u32 reg;
+
+	reg = dwc_pwm_readl(dwc, DWC_TIM_CTRL(pwm));
+
+	if (enabled)
+		reg |= DWC_TIM_CTRL_EN;
+	else
+		reg &= ~DWC_TIM_CTRL_EN;
+
+	dwc_pwm_writel(dwc, reg, DWC_TIM_CTRL(pwm));
+}
+
+static int __dwc_pwm_configure_timer(struct dwc_pwm *dwc,
+				     struct pwm_device *pwm,
+				     const struct pwm_state *state)
+{
+	u64 tmp;
+	u32 ctrl;
+	u32 high;
+	u32 low;
+
+	/*
+	 * Calculate width of low and high period in terms of input clock
+	 * periods and check are the result within HW limits between 1 and
+	 * 2^32 periods.
+	 */
+	tmp = DIV_ROUND_CLOSEST_ULL(state->duty_cycle, DWC_CLK_PERIOD_NS);
+	if (tmp < 1 || tmp > (1ULL << 32))
+		return -ERANGE;
+	low = tmp - 1;
+
+	tmp = DIV_ROUND_CLOSEST_ULL(state->period - state->duty_cycle,
+				    DWC_CLK_PERIOD_NS);
+	if (tmp < 1 || tmp > (1ULL << 32))
+		return -ERANGE;
+	high = tmp - 1;
+
+	/*
+	 * Specification says timer usage flow is to disable timer, then
+	 * program it followed by enable. It also says Load Count is loaded
+	 * into timer after it is enabled - either after a disable or
+	 * a reset. Based on measurements it happens also without disable
+	 * whenever Load Count is updated. But follow the specification.
+	 */
+	__dwc_pwm_set_enable(dwc, pwm->hwpwm, false);
+
+	/*
+	 * Write Load Count and Load Count 2 registers. Former defines the
+	 * width of low period and latter the width of high period in terms
+	 * multiple of input clock periods:
+	 * Width = ((Count + 1) * input clock period).
+	 */
+	dwc_pwm_writel(dwc, low, DWC_TIM_LD_CNT(pwm->hwpwm));
+	dwc_pwm_writel(dwc, high, DWC_TIM_LD_CNT2(pwm->hwpwm));
+
+	/*
+	 * Set user-defined mode, timer reloads from Load Count registers
+	 * when it counts down to 0.
+	 * Set PWM mode, it makes output to toggle and width of low and high
+	 * periods are set by Load Count registers.
+	 */
+	ctrl = DWC_TIM_CTRL_MODE_USER | DWC_TIM_CTRL_PWM;
+	dwc_pwm_writel(dwc, ctrl, DWC_TIM_CTRL(pwm->hwpwm));
+
+	/*
+	 * Enable timer. Output starts from low period.
+	 */
+	__dwc_pwm_set_enable(dwc, pwm->hwpwm, state->enabled);
+
+	return 0;
+}
+
+static int dwc_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			 const struct pwm_state *state)
+{
+	struct dwc_pwm *dwc = to_dwc_pwm(chip);
+
+	if (state->polarity != PWM_POLARITY_INVERSED)
+		return -EINVAL;
+
+	if (state->enabled) {
+		if (!pwm->state.enabled)
+			pm_runtime_get_sync(chip->dev);
+		return __dwc_pwm_configure_timer(dwc, pwm, state);
+	} else {
+		if (pwm->state.enabled) {
+			__dwc_pwm_set_enable(dwc, pwm->hwpwm, false);
+			pm_runtime_put_sync(chip->dev);
+		}
+	}
+
+	return 0;
+}
+
+static void dwc_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			      struct pwm_state *state)
+{
+	struct dwc_pwm *dwc = to_dwc_pwm(chip);
+	u64 duty, period;
+
+	pm_runtime_get_sync(chip->dev);
+
+	state->enabled = !!(dwc_pwm_readl(dwc,
+				DWC_TIM_CTRL(pwm->hwpwm)) & DWC_TIM_CTRL_EN);
+
+	duty = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(pwm->hwpwm));
+	duty += 1;
+	duty *= DWC_CLK_PERIOD_NS;
+	state->duty_cycle = duty;
+
+	period = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(pwm->hwpwm));
+	period += 1;
+	period *= DWC_CLK_PERIOD_NS;
+	period += duty;
+	state->period = period;
+
+	state->polarity = PWM_POLARITY_INVERSED;
+
+	pm_runtime_put_sync(chip->dev);
+}
+
+static const struct pwm_ops dwc_pwm_ops = {
+	.apply = dwc_pwm_apply,
+	.get_state = dwc_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int dwc_pwm_probe(struct pci_dev *pci, const struct pci_device_id *id)
+{
+	struct device *dev = &pci->dev;
+	struct dwc_pwm *dwc;
+	int ret;
+
+	dwc = devm_kzalloc(&pci->dev, sizeof(*dwc), GFP_KERNEL);
+	if (!dwc)
+		return -ENOMEM;
+
+	ret = pcim_enable_device(pci);
+	if (ret) {
+		dev_err(&pci->dev,
+			"Failed to enable device (%pe)\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	pci_set_master(pci);
+
+	ret = pcim_iomap_regions(pci, BIT(0), pci_name(pci));
+	if (ret) {
+		dev_err(&pci->dev,
+			"Failed to iomap PCI BAR (%pe)\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	dwc->base = pcim_iomap_table(pci)[0];
+	if (!dwc->base) {
+		dev_err(&pci->dev, "Base address missing\n");
+		return -ENOMEM;
+	}
+
+	pci_set_drvdata(pci, dwc);
+
+	dwc->chip.dev = dev;
+	dwc->chip.ops = &dwc_pwm_ops;
+	dwc->chip.npwm = DWC_TIMERS_TOTAL;
+	dwc->chip.base = -1;
+
+	ret = pwmchip_add(&dwc->chip);
+	if (ret)
+		return ret;
+
+	pm_runtime_put(dev);
+	pm_runtime_allow(dev);
+
+	return 0;
+}
+
+static void dwc_pwm_remove(struct pci_dev *pci)
+{
+	struct dwc_pwm *dwc = pci_get_drvdata(pci);
+
+	pm_runtime_forbid(&pci->dev);
+	pm_runtime_get_noresume(&pci->dev);
+
+	pwmchip_remove(&dwc->chip);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int dwc_pwm_suspend(struct device *dev)
+{
+	struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
+	struct dwc_pwm *dwc = pci_get_drvdata(pdev);
+	int i;
+
+	for (i = 0; i < DWC_TIMERS_TOTAL; i++) {
+		if (dwc->chip.pwms[i].state.enabled) {
+			dev_err(dev, "PWM %u in use by consumer (%s)\n",
+				i, dwc->chip.pwms[i].label);
+			return -EBUSY;
+		}
+		dwc->ctx[i].cnt = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(i));
+		dwc->ctx[i].cnt2 = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(i));
+		dwc->ctx[i].ctrl = dwc_pwm_readl(dwc, DWC_TIM_CTRL(i));
+	}
+
+	return 0;
+}
+
+static int dwc_pwm_resume(struct device *dev)
+{
+	struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
+	struct dwc_pwm *dwc = pci_get_drvdata(pdev);
+	int i;
+
+	for (i = 0; i < DWC_TIMERS_TOTAL; i++) {
+		dwc_pwm_writel(dwc, dwc->ctx[i].cnt, DWC_TIM_LD_CNT(i));
+		dwc_pwm_writel(dwc, dwc->ctx[i].cnt2, DWC_TIM_LD_CNT2(i));
+		dwc_pwm_writel(dwc, dwc->ctx[i].ctrl, DWC_TIM_CTRL(i));
+	}
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(dwc_pwm_pm_ops, dwc_pwm_suspend, dwc_pwm_resume);
+
+static const struct pci_device_id dwc_pwm_id_table[] = {
+	{ PCI_VDEVICE(INTEL, 0x4bb7) }, /* Elkhart Lake */
+	{  }	/* Terminating Entry */
+};
+MODULE_DEVICE_TABLE(pci, dwc_pwm_id_table);
+
+static struct pci_driver dwc_pwm_driver = {
+	.name = "pwm-dwc",
+	.probe = dwc_pwm_probe,
+	.remove = dwc_pwm_remove,
+	.id_table = dwc_pwm_id_table,
+	.driver = {
+		.pm = &dwc_pwm_pm_ops,
+	},
+};
+
+module_pci_driver(dwc_pwm_driver);
+
+MODULE_AUTHOR("Felipe Balbi (Intel)");
+MODULE_AUTHOR("Jarkko Nikula <jarkko.nikula@linux.intel.com>");
+MODULE_AUTHOR("Raymond Tan <raymond.tan@intel.com>");
+MODULE_DESCRIPTION("DesignWare PWM Controller");
+MODULE_LICENSE("GPL");