drivers/pwm/pwm-xilinx.c - linux - Git at Google

 // 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)

 static inline struct xilinx_timer_priv
 *xilinx_pwm_chip_to_priv(struct pwm_chip *chip)
 {
 	return pwmchip_get_drvdata(chip);
 }

 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 int 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;

 	return 0;
 }

 static const struct pwm_ops xilinx_pwm_ops = {
 	.apply = xilinx_pwm_apply,
 	.get_state = xilinx_pwm_get_state,
 };

 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 pwm_chip *chip;
 	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");

 	chip = devm_pwmchip_alloc(dev, 1, sizeof(*priv));
 	if (IS_ERR(chip))
 		return PTR_ERR(chip);
 	priv = xilinx_pwm_chip_to_priv(chip);

 	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_enabled(dev, "s_axi_aclk");
 	if (IS_ERR(priv->clk))
 		return dev_err_probe(dev, PTR_ERR(priv->clk),
 				     "Could not get clock\n");

 	ret = devm_clk_rate_exclusive_get(dev, priv->clk);
 	if (ret)
 		return dev_err_probe(dev, ret,
 				     "Failed to lock clock rate\n");

 	chip->ops = &xilinx_pwm_ops;
 	ret = devm_pwmchip_add(dev, chip);
 	if (ret)
 		return dev_err_probe(dev, ret, "Could not register PWM chip\n");

 	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,
 	.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");
	// 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)

	static inline struct xilinx_timer_priv
	xilinx_pwm_chip_to_priv(struct pwm_chip chip)
	{
	return pwmchip_get_drvdata(chip);
	}

	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 int 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;

	return 0;
	}

	static const struct pwm_ops xilinx_pwm_ops = {
	.apply = xilinx_pwm_apply,
	.get_state = xilinx_pwm_get_state,
	};

	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 pwm_chip *chip;
	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");

	chip = devm_pwmchip_alloc(dev, 1, sizeof(*priv));
	if (IS_ERR(chip))
	return PTR_ERR(chip);
	priv = xilinx_pwm_chip_to_priv(chip);

	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_enabled(dev, "s_axi_aclk");
	if (IS_ERR(priv->clk))
	return dev_err_probe(dev, PTR_ERR(priv->clk),
	"Could not get clock\n");

	ret = devm_clk_rate_exclusive_get(dev, priv->clk);
	if (ret)
	return dev_err_probe(dev, ret,
	"Failed to lock clock rate\n");

	chip->ops = &xilinx_pwm_ops;
	ret = devm_pwmchip_add(dev, chip);
	if (ret)
	return dev_err_probe(dev, ret, "Could not register PWM chip\n");

	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,
	.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");