[PATCH 2/2] pwm: Add support for Xilinx AXI Timer

[Sean Anderson]

This adds PWM support for Xilinx LogiCORE IP AXI soft timers commonly
found on Xilinx FPGAs. There is another driver for this device located
at arch/microblaze/kernel/timer.c, but it is only used for timekeeping.
This driver was written with reference to Xilinx DS764 for v1.03.a [1].

[1] https://www.xilinx.com/support/documentation/ip_documentation/axi_timer/v1_03_a/axi_timer_ds764.pdf

Signed-off-by: Sean Anderson <sean.anderson@xxxxxxxx>

---

 arch/arm64/configs/defconfig |   1 +
 drivers/pwm/Kconfig          |  11 ++
 drivers/pwm/Makefile         |   1 +
 drivers/pwm/pwm-xilinx.c     | 322 +++++++++++++++++++++++++++++++++++
 4 files changed, 335 insertions(+)
 create mode 100644 drivers/pwm/pwm-xilinx.c

diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig
index 08c6f769df9a..81794209f287 100644
--- a/arch/arm64/configs/defconfig
+++ b/arch/arm64/configs/defconfig
@@ -1083,6 +1083,7 @@ CONFIG_PWM_SAMSUNG=y
 CONFIG_PWM_SL28CPLD=m
 CONFIG_PWM_SUN4I=m
 CONFIG_PWM_TEGRA=m
+CONFIG_PWM_XILINX=m
 CONFIG_SL28CPLD_INTC=y
 CONFIG_QCOM_PDC=y
 CONFIG_RESET_IMX7=y
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index d3371ac7b871..01e62928f4bf 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -628,4 +628,15 @@ config PWM_VT8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-vt8500.
 
+config PWM_XILINX
+	tristate "Xilinx AXI Timer PWM support"
+	depends on !MICROBLAZE
+	help
+	  PWM framework driver for Xilinx LogiCORE IP AXI Timers. This
+	  timer is typically a soft core which may be present in Xilinx
+	  FPGAs. If you don't have this IP in your design, choose N.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-xilinx.
+
 endif
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index d3879619bd76..fc1bd6ccc9ed 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -59,3 +59,4 @@ obj-$(CONFIG_PWM_TIEHRPWM)	+= pwm-tiehrpwm.o
 obj-$(CONFIG_PWM_TWL)		+= pwm-twl.o
 obj-$(CONFIG_PWM_TWL_LED)	+= pwm-twl-led.o
 obj-$(CONFIG_PWM_VT8500)	+= pwm-vt8500.o
+obj-$(CONFIG_PWM_XILINX)	+= pwm-xilinx.o
diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c
new file mode 100644
index 000000000000..240bd2993f97
--- /dev/null
+++ b/drivers/pwm/pwm-xilinx.c
@@ -0,0 +1,322 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Sean Anderson <sean.anderson@xxxxxxxx>
+ */
+#include <asm/io.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#define TCSR0	0x00
+#define TLR0	0x04
+#define TCR0	0x08
+#define TCSR1	0x10
+#define TLR1	0x14
+#define TCR1	0x18
+
+#define TCSR_MDT	BIT(0)
+#define TCSR_UDT	BIT(1)
+#define TCSR_GENT	BIT(2)
+#define TCSR_CAPT	BIT(3)
+#define TCSR_ARHT	BIT(4)
+#define TCSR_LOAD	BIT(5)
+#define TCSR_ENIT	BIT(6)
+#define TCSR_ENT	BIT(7)
+#define TCSR_TINT	BIT(8)
+#define TCSR_PWMA	BIT(9)
+#define TCSR_ENALL	BIT(10)
+#define TCSR_CASC	BIT(11)
+
+/* Bits we need to set/clear to enable PWM mode, not including CASC */
+#define TCSR_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA)
+#define TCSR_CLEAR (TCSR_MDT | TCSR_LOAD)
+
+#define NSEC_PER_SEC_ULL 1000000000ULL
+
+/**
+ * struct xilinx_pwm_device - Driver data for Xilinx AXI timer PWM driver
+ * @chip: PWM controller chip
+ * @clk: Parent clock
+ * @regs: Base address of this device
+ * @width: Width of the counters, in bits
+ */
+struct xilinx_pwm_device {
+	struct pwm_chip chip;
+	struct clk *clk;
+	void __iomem *regs;
+	unsigned int width;
+};
+
+static inline struct xilinx_pwm_device *xilinx_pwm_chip_to_device(struct pwm_chip *chip)
+{
+	return container_of(chip, struct xilinx_pwm_device, chip);
+}
+
+static bool xilinx_pwm_is_enabled(u32 tcsr0, u32 tcsr1)
+{
+	return !(~tcsr0 & TCSR_SET || tcsr0 & (TCSR_CLEAR | TCSR_CASC) ||
+		 ~tcsr1 & TCSR_SET || tcsr1 & TCSR_CLEAR);
+}
+
+static u32 xilinx_pwm_calc_tlr(struct xilinx_pwm_device *pwm, u32 tcsr,
+			       unsigned int period)
+{
+	u64 cycles = DIV_ROUND_DOWN_ULL(period * clk_get_rate(pwm->clk),
+					NSEC_PER_SEC_ULL);
+
+	if (tcsr & TCSR_UDT)
+		return cycles - 2;
+	else
+		return (BIT_ULL(pwm->width) - 1) - cycles + 2;
+}
+
+static unsigned int xilinx_pwm_get_period(struct xilinx_pwm_device *pwm,
+					  u32 tlr, u32 tcsr)
+{
+	u64 cycles;
+
+	if (tcsr & TCSR_UDT)
+		cycles = tlr + 2;
+	else
+		cycles = (BIT_ULL(pwm->width) - 1) - tlr + 2;
+
+	return DIV_ROUND_DOWN_ULL(cycles * NSEC_PER_SEC_ULL,
+				  clk_get_rate(pwm->clk));
+}
+
+static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused,
+			    const struct pwm_state *state)
+{
+	struct xilinx_pwm_device *pwm = xilinx_pwm_chip_to_device(chip);
+	u32 tlr0, tlr1;
+	u32 tcsr0 = readl(pwm->regs + TCSR0);
+	u32 tcsr1 = readl(pwm->regs + TCSR1);
+	bool enabled = xilinx_pwm_is_enabled(tcsr0, tcsr1);
+
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
+
+	if (!enabled && state->enabled)
+		clk_rate_exclusive_get(pwm->clk);
+
+	tlr0 = xilinx_pwm_calc_tlr(pwm, tcsr0, state->period);
+	tlr1 = xilinx_pwm_calc_tlr(pwm, tcsr1, state->duty_cycle);
+	writel(tlr0, pwm->regs + TLR0);
+	writel(tlr1, pwm->regs + TLR1);
+
+	if (state->enabled) {
+		/* Only touch the TCSRs if we aren't already running */
+		if (!enabled) {
+			/* Load TLR into TCR */
+			writel(tcsr0 | TCSR_LOAD, pwm->regs + TCSR0);
+			writel(tcsr1 | TCSR_LOAD, pwm->regs + TCSR1);
+			/* Enable timers all at once with ENALL */
+			tcsr0 = (TCSR_SET & ~TCSR_ENT) | (tcsr0 & TCSR_UDT);
+			tcsr1 = TCSR_SET | TCSR_ENALL | (tcsr1 & TCSR_UDT);
+			writel(tcsr0, pwm->regs + TCSR0);
+			writel(tcsr1, pwm->regs + TCSR1);
+		}
+	} else {
+		writel(tcsr0 & ~TCSR_ENT, pwm->regs + TCSR0);
+		writel(tcsr1 & ~TCSR_ENT, pwm->regs + TCSR1);
+	}
+
+	if (enabled && !state->enabled)
+		clk_rate_exclusive_put(pwm->clk);
+
+	return 0;
+}
+
+static void xilinx_pwm_get_state(struct pwm_chip *chip,
+				 struct pwm_device *unused,
+				 struct pwm_state *state)
+{
+	struct xilinx_pwm_device *pwm = xilinx_pwm_chip_to_device(chip);
+	u32 tlr0, tlr1, tcsr0, tcsr1;
+
+	tlr0 = readl(pwm->regs + TLR0);
+	tlr1 = readl(pwm->regs + TLR1);
+	tcsr0 = readl(pwm->regs + TCSR0);
+	tcsr1 = readl(pwm->regs + TCSR1);
+
+	state->period = xilinx_pwm_get_period(pwm, tlr0, tcsr0);
+	state->duty_cycle = xilinx_pwm_get_period(pwm, tlr1, tcsr1);
+	state->enabled = xilinx_pwm_is_enabled(tcsr0, tcsr1);
+	state->polarity = PWM_POLARITY_NORMAL;
+}
+
+static const struct pwm_ops xilinx_pwm_ops = {
+	.apply = xilinx_pwm_apply,
+	.get_state = xilinx_pwm_get_state,
+};
+
+static struct dentry *debug_dir;
+
+#define DEBUG_REG(reg) { .name = #reg, .offset = (reg), }
+static struct debugfs_reg32 xilinx_pwm_reg32[] = {
+	DEBUG_REG(TCSR0),
+	DEBUG_REG(TLR0),
+	DEBUG_REG(TCR0),
+	DEBUG_REG(TCSR1),
+	DEBUG_REG(TLR1),
+	DEBUG_REG(TCR1),
+};
+
+static int xilinx_pwm_debug_create(struct xilinx_pwm_device *pwm)
+{
+	struct debugfs_regset32 *regset;
+
+	if (!IS_ENABLED(CONFIG_DEBUG_FS))
+		return 0;
+
+	regset = devm_kzalloc(pwm->chip.dev, sizeof(*regset), GFP_KERNEL);
+	if (!pwm)
+		return -ENOMEM;
+
+	regset->regs = xilinx_pwm_reg32;
+	regset->nregs = ARRAY_SIZE(xilinx_pwm_reg32);
+	regset->base = pwm->regs;
+
+	debugfs_create_regset32(dev_name(pwm->chip.dev), 0400, debug_dir,
+				regset);
+	return 0;
+}
+
+static int xilinx_pwm_probe(struct platform_device *pdev)
+{
+	bool enabled;
+	int i, ret;
+	struct device *dev = &pdev->dev;
+	struct xilinx_pwm_device *pwm;
+	u32 one_timer;
+
+	ret = of_property_read_u32(dev->of_node, "xlnx,one-timer-only",
+				   &one_timer);
+	if (ret || one_timer) {
+		dev_err(dev, "two timers are needed for PWM mode\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < 2; i++) {
+		char fmt[] = "xlnx,gen%u-assert";
+		char buf[sizeof(fmt)];
+		u32 gen;
+
+		snprintf(buf, sizeof(buf), fmt, i);
+		ret = of_property_read_u32(dev->of_node, buf, &gen);
+		if (ret || !gen) {
+			dev_err(dev, "generateout%u must be active high\n", i);
+			return -EINVAL;
+		}
+	}
+
+	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+	if (!pwm)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, pwm);
+
+	pwm->chip.dev = &pdev->dev;
+	pwm->chip.ops = &xilinx_pwm_ops;
+	pwm->chip.base = -1;
+	pwm->chip.npwm = 1;
+
+	pwm->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pwm->regs))
+		return PTR_ERR(pwm->regs);
+
+	ret = of_property_read_u32(dev->of_node, "xlnx,count-width", &pwm->width);
+	if (ret) {
+		dev_err(dev, "missing counter width\n");
+		return -EINVAL;
+	}
+
+	pwm->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(pwm->clk))
+		return dev_err_probe(dev, PTR_ERR(pwm->clk), "missing clock\n");
+
+	ret = clk_prepare_enable(pwm->clk);
+	if (ret) {
+		dev_err(dev, "clock enable failed\n");
+		return ret;
+	}
+
+	ret = xilinx_pwm_debug_create(pwm);
+	if (ret) {
+		clk_disable_unprepare(pwm->clk);
+		return ret;
+	}
+
+	ret = pwmchip_add(&pwm->chip);
+	if (ret) {
+		clk_disable_unprepare(pwm->clk);
+		return ret;
+	}
+
+	enabled = xilinx_pwm_is_enabled(readl(pwm->regs + TCSR0),
+					readl(pwm->regs + TCSR1));
+	if (enabled)
+		clk_rate_exclusive_get(pwm->clk);
+
+	return ret;
+}
+
+static int xilinx_pwm_remove(struct platform_device *pdev)
+{
+	struct xilinx_pwm_device *pwm = platform_get_drvdata(pdev);
+	bool enabled = xilinx_pwm_is_enabled(readl(pwm->regs + TCSR0),
+					     readl(pwm->regs + TCSR1));
+
+	if (enabled)
+		clk_rate_exclusive_put(pwm->clk);
+	clk_disable_unprepare(pwm->clk);
+	return pwmchip_remove(&pwm->chip);
+}
+
+static const struct of_device_id xilinx_pwm_of_match[] = {
+	{ .compatible = "xlnx,xps-timer-1.00.a" },
+	{ .compatible = "xlnx,axi-timer-2.0" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, xilinx_pwm_of_match);
+
+static struct platform_driver xilinx_pwm_driver = {
+	.probe = xilinx_pwm_probe,
+	.remove = xilinx_pwm_remove,
+	.driver = {
+		.name = "xilinx-pwm",
+		.of_match_table = of_match_ptr(xilinx_pwm_of_match),
+	},
+};
+
+static int __init xilinx_pwm_init(void)
+{
+	int ret = platform_driver_register(&xilinx_pwm_driver);
+
+	if (ret)
+		return ret;
+
+	if (IS_ENABLED(CONFIG_DEBUG_FS)) {
+		debug_dir = debugfs_create_dir(xilinx_pwm_driver.driver.name, NULL);
+		if (IS_ERR(debug_dir)) {
+			platform_driver_unregister(&xilinx_pwm_driver);
+			return PTR_ERR(debug_dir);
+		}
+	}
+	return 0;
+}
+module_init(xilinx_pwm_init);
+
+static void __exit xilinx_pwm_exit(void)
+{
+	platform_driver_unregister(&xilinx_pwm_driver);
+	if (IS_ENABLED(CONFIG_DEBUG_FS))
+		debugfs_remove_recursive(debug_dir);
+}
+module_exit(xilinx_pwm_exit);
+
+MODULE_ALIAS("platform:xilinx-pwm");
+MODULE_DESCRIPTION("Xilinx LogiCORE IP AXI Timer PWM driver");
+MODULE_LICENSE("GPL v2");
-- 
2.25.1