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Commit 1e70897d authored by Naidu Tellapati's avatar Naidu Tellapati Committed by Thierry Reding
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pwm: img: Impose upper and lower timebase steps value 



The PWM hardware on Pistachio platform has a maximum timebase steps
value to 255. To fix it, let's introduce a compatible-specific
data structure to contain the SoC-specific details and use it to
specify a maximum timebase.

Also, let's limit the minimum timebase to 16 steps, to allow a sane
range of duty cycle steps.

Fixes: 277bb6a2 ("pwm: Imagination Technologies PWM DAC driver")
Signed-off-by: default avatarNaidu Tellapati <naidu.tellapati@imgtec.com>
Signed-off-by: default avatarEzequiel Garcia <ezequiel.garcia@imgtec.com>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent b787f68c

drivers/pwm/pwm-img.c

+64 −12
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/mfd/syscon.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/of_device.h>

#include <linux/platform_device.h>

#include <linux/pwm.h>

#include <linux/regmap.h>
@@ -38,7 +39,22 @@ 
#define PERIP_PWM_PDM_CONTROL_CH_MASK		0x1

#define PERIP_PWM_PDM_CONTROL_CH_SHIFT(ch)	((ch) * 4)



#define MAX_TMBASE_STEPS			65536

/*

 * PWM period is specified with a timebase register,

 * in number of step periods. The PWM duty cycle is also

 * specified in step periods, in the [0, $timebase] range.

 * In other words, the timebase imposes the duty cycle

 * resolution. Therefore, let's constraint the timebase to

 * a minimum value to allow a sane range of duty cycle values.

 * Imposing a minimum timebase, will impose a maximum PWM frequency.

 *

 * The value chosen is completely arbitrary.

 */

#define MIN_TMBASE_STEPS			16



struct img_pwm_soc_data {

	u32 max_timebase;

};



struct img_pwm_chip {

	struct device	*dev;
@@ -47,6 +63,9 @@ struct img_pwm_chip { 
	struct clk	*sys_clk;

	void __iomem	*base;

	struct regmap	*periph_regs;

	int		max_period_ns;

	int		min_period_ns;

	const struct img_pwm_soc_data   *data;

};



static inline struct img_pwm_chip *to_img_pwm_chip(struct pwm_chip *chip)
@@ -72,24 +91,31 @@ static int img_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, 
	u32 val, div, duty, timebase;

	unsigned long mul, output_clk_hz, input_clk_hz;

	struct img_pwm_chip *pwm_chip = to_img_pwm_chip(chip);

	unsigned int max_timebase = pwm_chip->data->max_timebase;



	if (period_ns < pwm_chip->min_period_ns ||

	    period_ns > pwm_chip->max_period_ns) {

		dev_err(chip->dev, "configured period not in range\n");

		return -ERANGE;

	}



	input_clk_hz = clk_get_rate(pwm_chip->pwm_clk);

	output_clk_hz = DIV_ROUND_UP(NSEC_PER_SEC, period_ns);



	mul = DIV_ROUND_UP(input_clk_hz, output_clk_hz);

	if (mul <= MAX_TMBASE_STEPS) {

	if (mul <= max_timebase) {

		div = PWM_CTRL_CFG_NO_SUB_DIV;

		timebase = DIV_ROUND_UP(mul, 1);

	} else if (mul <= MAX_TMBASE_STEPS * 8) {

	} else if (mul <= max_timebase * 8) {

		div = PWM_CTRL_CFG_SUB_DIV0;

		timebase = DIV_ROUND_UP(mul, 8);

	} else if (mul <= MAX_TMBASE_STEPS * 64) {

	} else if (mul <= max_timebase * 64) {

		div = PWM_CTRL_CFG_SUB_DIV1;

		timebase = DIV_ROUND_UP(mul, 64);

	} else if (mul <= MAX_TMBASE_STEPS * 512) {

	} else if (mul <= max_timebase * 512) {

		div = PWM_CTRL_CFG_SUB_DIV0_DIV1;

		timebase = DIV_ROUND_UP(mul, 512);

	} else if (mul > MAX_TMBASE_STEPS * 512) {

	} else if (mul > max_timebase * 512) {

		dev_err(chip->dev,

			"failed to configure timebase steps/divider value\n");

		return -EINVAL;
@@ -143,11 +169,27 @@ static const struct pwm_ops img_pwm_ops = { 
	.owner = THIS_MODULE,

};



static const struct img_pwm_soc_data pistachio_pwm = {

	.max_timebase = 255,

};



static const struct of_device_id img_pwm_of_match[] = {

	{

		.compatible = "img,pistachio-pwm",

		.data = &pistachio_pwm,

	},

	{ }

};

MODULE_DEVICE_TABLE(of, img_pwm_of_match);



static int img_pwm_probe(struct platform_device *pdev)

{

	int ret;

	u64 val;

	unsigned long clk_rate;

	struct resource *res;

	struct img_pwm_chip *pwm;

	const struct of_device_id *of_dev_id;



	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);

	if (!pwm)
@@ -160,6 +202,11 @@ static int img_pwm_probe(struct platform_device *pdev) 
	if (IS_ERR(pwm->base))

		return PTR_ERR(pwm->base);



	of_dev_id = of_match_device(img_pwm_of_match, &pdev->dev);

	if (!of_dev_id)

		return -ENODEV;

	pwm->data = of_dev_id->data;



	pwm->periph_regs = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,

							   "img,cr-periph");

	if (IS_ERR(pwm->periph_regs))
@@ -189,6 +236,17 @@ static int img_pwm_probe(struct platform_device *pdev) 
		goto disable_sysclk;

	}



	clk_rate = clk_get_rate(pwm->pwm_clk);



	/* The maximum input clock divider is 512 */

	val = (u64)NSEC_PER_SEC * 512 * pwm->data->max_timebase;

	do_div(val, clk_rate);

	pwm->max_period_ns = val;



	val = (u64)NSEC_PER_SEC * MIN_TMBASE_STEPS;

	do_div(val, clk_rate);

	pwm->min_period_ns = val;



	pwm->chip.dev = &pdev->dev;

	pwm->chip.ops = &img_pwm_ops;

	pwm->chip.base = -1;
@@ -228,12 +286,6 @@ static int img_pwm_remove(struct platform_device *pdev) 
	return pwmchip_remove(&pwm_chip->chip);

}



static const struct of_device_id img_pwm_of_match[] = {

	{ .compatible = "img,pistachio-pwm", },

	{ }

};

MODULE_DEVICE_TABLE(of, img_pwm_of_match);



static struct platform_driver img_pwm_driver = {

	.driver = {

		.name = "img-pwm",