--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Sean Anderson <sean.anderson@seco.com>
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we may end up with one cycle
+ * with the old duty cycle and the new period. This is because the counters
+ * may only be reloaded by first stopping them, or by letting them be
+ * automatically reloaded at the end of a cycle. If this automatic reload
+ * happens after we set TLR0 but before we set TLR1 then we will have a
+ * bad cycle. This could probably be fixed by reading TCR0 just before
+ * reprogramming, but I think it would add complexity for little gain.
+ * - Cannot produce 100% duty cycle by configuring the TLRs. This might be
+ * possible by stopping the counters at an appropriate point in the cycle,
+ * but this is not (yet) implemented.
+ * - Only produces "normal" output.
+ * - Always produces low output if disabled.
+ */
+
+#include <clocksource/timer-xilinx.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+
+/*
+ * The following functions are "common" to drivers for this device, and may be
+ * exported at a future date.
+ */
+u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr,
+ u64 cycles)
+{
+ WARN_ON(cycles < 2 || cycles - 2 > priv->max);
+
+ if (tcsr & TCSR_UDT)
+ return cycles - 2;
+ return priv->max - cycles + 2;
+}
+
+unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv,
+ u32 tlr, u32 tcsr)
+{
+ u64 cycles;
+
+ if (tcsr & TCSR_UDT)
+ cycles = tlr + 2;
+ else
+ cycles = (u64)priv->max - tlr + 2;
+
+ /* cycles has a max of 2^32 + 2, so we can't overflow */
+ return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC,
+ clk_get_rate(priv->clk));
+}
+
+/*
+ * The idea here is to capture whether the PWM is actually running (e.g.
+ * because we or the bootloader set it up) and we need to be careful to ensure
+ * we don't cause a glitch. According to the data sheet, to enable the PWM we
+ * need to
+ *
+ * - Set both timers to generate mode (MDT=1)
+ * - Set both timers to PWM mode (PWMA=1)
+ * - Enable the generate out signals (GENT=1)
+ *
+ * In addition,
+ *
+ * - The timer must be running (ENT=1)
+ * - The timer must auto-reload TLR into TCR (ARHT=1)
+ * - We must not be in the process of loading TLR into TCR (LOAD=0)
+ * - Cascade mode must be disabled (CASC=0)
+ *
+ * If any of these differ from usual, then the PWM is either disabled, or is
+ * running in a mode that this driver does not support.
+ */
+#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT | TCSR_PWMA)
+#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD)
+#define TCSR_PWM_MASK (TCSR_PWM_SET | TCSR_PWM_CLEAR)
+
+struct xilinx_pwm_device {
+ struct pwm_chip chip;
+ struct xilinx_timer_priv priv;
+};
+
+static inline struct xilinx_timer_priv
+*xilinx_pwm_chip_to_priv(struct pwm_chip *chip)
+{
+ return &container_of(chip, struct xilinx_pwm_device, chip)->priv;
+}
+
+static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1)
+{
+ return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) == TCSR_PWM_SET &&
+ (TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET;
+}
+
+static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device *unused,
+ const struct pwm_state *state)
+{
+ struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip);
+ u32 tlr0, tlr1, tcsr0, tcsr1;
+ u64 period_cycles, duty_cycles;
+ unsigned long rate;
+
+ if (state->polarity != PWM_POLARITY_NORMAL)
+ return -EINVAL;
+
+ /*
+ * To be representable by TLR, cycles must be between 2 and
+ * priv->max + 2. To enforce this we can reduce the cycles, but we may
+ * not increase them. Caveat emptor: while this does result in more
+ * predictable rounding, it may also result in a completely different
+ * duty cycle (% high time) than what was requested.
+ */
+ rate = clk_get_rate(priv->clk);
+ /* Avoid overflow */
+ period_cycles = min_t(u64, state->period, U32_MAX * NSEC_PER_SEC);
+ period_cycles = mul_u64_u32_div(period_cycles, rate, NSEC_PER_SEC);
+ period_cycles = min_t(u64, period_cycles, priv->max + 2);
+ if (period_cycles < 2)
+ return -ERANGE;
+
+ /* Same thing for duty cycles */
+ duty_cycles = min_t(u64, state->duty_cycle, U32_MAX * NSEC_PER_SEC);
+ duty_cycles = mul_u64_u32_div(duty_cycles, rate, NSEC_PER_SEC);
+ duty_cycles = min_t(u64, duty_cycles, priv->max + 2);
+
+ /*
+ * If we specify 100% duty cycle, we will get 0% instead, so decrease
+ * the duty cycle count by one.
+ */
+ if (duty_cycles >= period_cycles)
+ duty_cycles = period_cycles - 1;
+
+ /* Round down to 0% duty cycle for unrepresentable duty cycles */
+ if (duty_cycles < 2)
+ duty_cycles = period_cycles;
+
+ regmap_read(priv->map, TCSR0, &tcsr0);
+ regmap_read(priv->map, TCSR1, &tcsr1);
+ tlr0 = xilinx_timer_tlr_cycles(priv, tcsr0, period_cycles);
+ tlr1 = xilinx_timer_tlr_cycles(priv, tcsr1, duty_cycles);
+ regmap_write(priv->map, TLR0, tlr0);
+ regmap_write(priv->map, TLR1, tlr1);
+
+ if (state->enabled) {
+ /*
+ * If the PWM is already running, then the counters will be
+ * reloaded at the end of the current cycle.
+ */
+ if (!xilinx_timer_pwm_enabled(tcsr0, tcsr1)) {
+ /* Load TLR into TCR */
+ regmap_write(priv->map, TCSR0, tcsr0 | TCSR_LOAD);
+ regmap_write(priv->map, TCSR1, tcsr1 | TCSR_LOAD);
+ /* Enable timers all at once with ENALL */
+ tcsr0 = (TCSR_PWM_SET & ~TCSR_ENT) | (tcsr0 & TCSR_UDT);
+ tcsr1 = TCSR_PWM_SET | TCSR_ENALL | (tcsr1 & TCSR_UDT);
+ regmap_write(priv->map, TCSR0, tcsr0);
+ regmap_write(priv->map, TCSR1, tcsr1);
+ }
+ } else {
+ regmap_write(priv->map, TCSR0, 0);
+ regmap_write(priv->map, TCSR1, 0);
+ }
+
+ return 0;
+}
+
+static void xilinx_pwm_get_state(struct pwm_chip *chip,
+ struct pwm_device *unused,
+ struct pwm_state *state)
+{
+ struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip);
+ u32 tlr0, tlr1, tcsr0, tcsr1;
+
+ regmap_read(priv->map, TLR0, &tlr0);
+ regmap_read(priv->map, TLR1, &tlr1);
+ regmap_read(priv->map, TCSR0, &tcsr0);
+ regmap_read(priv->map, TCSR1, &tcsr1);
+ state->period = xilinx_timer_get_period(priv, tlr0, tcsr0);
+ state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1);
+ state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1);
+ state->polarity = PWM_POLARITY_NORMAL;
+
+ /*
+ * 100% duty cycle results in constant low output. This may be (very)
+ * wrong if rate > 1 GHz, so fix this if you have such hardware :)
+ */
+ if (state->period == state->duty_cycle)
+ state->duty_cycle = 0;
+}
+
+static const struct pwm_ops xilinx_pwm_ops = {
+ .apply = xilinx_pwm_apply,
+ .get_state = xilinx_pwm_get_state,
+ .owner = THIS_MODULE,
+};
+
+static const struct regmap_config xilinx_pwm_regmap_config = {
+ .reg_bits = 32,
+ .reg_stride = 4,
+ .val_bits = 32,
+ .val_format_endian = REGMAP_ENDIAN_LITTLE,
+ .max_register = TCR1,
+};
+
+static int xilinx_pwm_probe(struct platform_device *pdev)
+{
+ int ret;
+ struct device *dev = &pdev->dev;
+ struct device_node *np = dev->of_node;
+ struct xilinx_timer_priv *priv;
+ struct xilinx_pwm_device *xilinx_pwm;
+ u32 pwm_cells, one_timer, width;
+ void __iomem *regs;
+
+ /* If there are no PWM cells, this binding is for a timer */
+ ret = of_property_read_u32(np, "#pwm-cells", &pwm_cells);
+ if (ret == -EINVAL)
+ return -ENODEV;
+ if (ret)
+ return dev_err_probe(dev, ret, "could not read #pwm-cells\n");
+
+ xilinx_pwm = devm_kzalloc(dev, sizeof(*xilinx_pwm), GFP_KERNEL);
+ if (!xilinx_pwm)
+ return -ENOMEM;
+ platform_set_drvdata(pdev, xilinx_pwm);
+ priv = &xilinx_pwm->priv;
+
+ regs = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(regs))
+ return PTR_ERR(regs);
+
+ priv->map = devm_regmap_init_mmio(dev, regs,
+ &xilinx_pwm_regmap_config);
+ if (IS_ERR(priv->map))
+ return dev_err_probe(dev, PTR_ERR(priv->map),
+ "Could not create regmap\n");
+
+ ret = of_property_read_u32(np, "xlnx,one-timer-only", &one_timer);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "Could not read xlnx,one-timer-only\n");
+
+ if (one_timer)
+ return dev_err_probe(dev, -EINVAL,
+ "Two timers required for PWM mode\n");
+
+ ret = of_property_read_u32(np, "xlnx,count-width", &width);
+ if (ret == -EINVAL)
+ width = 32;
+ else if (ret)
+ return dev_err_probe(dev, ret,
+ "Could not read xlnx,count-width\n");
+
+ if (width != 8 && width != 16 && width != 32)
+ return dev_err_probe(dev, -EINVAL,
+ "Invalid counter width %d\n", width);
+ priv->max = BIT_ULL(width) - 1;
+
+ /*
+ * The polarity of the Generate Out signals must be active high for PWM
+ * mode to work. We could determine this from the device tree, but
+ * alas, such properties are not allowed to be used.
+ */
+
+ priv->clk = devm_clk_get(dev, "s_axi_aclk");
+ if (IS_ERR(priv->clk))
+ return dev_err_probe(dev, PTR_ERR(priv->clk),
+ "Could not get clock\n");
+
+ ret = clk_prepare_enable(priv->clk);
+ if (ret)
+ return dev_err_probe(dev, ret, "Clock enable failed\n");
+ clk_rate_exclusive_get(priv->clk);
+
+ xilinx_pwm->chip.dev = dev;
+ xilinx_pwm->chip.ops = &xilinx_pwm_ops;
+ xilinx_pwm->chip.npwm = 1;
+ ret = pwmchip_add(&xilinx_pwm->chip);
+ if (ret) {
+ clk_rate_exclusive_put(priv->clk);
+ clk_disable_unprepare(priv->clk);
+ return dev_err_probe(dev, ret, "Could not register PWM chip\n");
+ }
+
+ return 0;
+}
+
+static int xilinx_pwm_remove(struct platform_device *pdev)
+{
+ struct xilinx_pwm_device *xilinx_pwm = platform_get_drvdata(pdev);
+
+ pwmchip_remove(&xilinx_pwm->chip);
+ clk_rate_exclusive_put(xilinx_pwm->priv.clk);
+ clk_disable_unprepare(xilinx_pwm->priv.clk);
+ return 0;
+}
+
+static const struct of_device_id xilinx_pwm_of_match[] = {
+ { .compatible = "xlnx,xps-timer-1.00.a", },
+ {},
+};
+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),
+ },
+};
+module_platform_driver(xilinx_pwm_driver);
+
+MODULE_ALIAS("platform:xilinx-pwm");
+MODULE_DESCRIPTION("PWM driver for Xilinx LogiCORE IP AXI Timer");
+MODULE_LICENSE("GPL");
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