Message-ID: <DB3PR0402MB3916E87140DE4A4242E879E9F5400@DB3PR0402MB3916.eurprd04.prod.outlook.com>
Date:   Tue, 19 Mar 2019 09:08:26 +0000
From:   Anson Huang <anson.huang@....com>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
CC:     "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "otavio@...ystems.com.br" <otavio@...ystems.com.br>,
        Leonard Crestez <leonard.crestez@....com>,
        "schnitzeltony@...il.com" <schnitzeltony@...il.com>,
        "jan.tuerk@...rion.com" <jan.tuerk@...rion.com>,
        Robin Gong <yibin.gong@....com>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH V6 2/5] pwm: Add i.MX TPM PWM driver support

Hi,

Best Regards!
Anson Huang

> -----Original Message-----
> From: Uwe Kleine-König [mailto:u.kleine-koenig@...gutronix.de]
> Sent: 2019年3月19日 16:04
> To: Anson Huang <anson.huang@....com>
> Cc: thierry.reding@...il.com; robh+dt@...nel.org; mark.rutland@....com;
> shawnguo@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> festevam@...il.com; linux@...linux.org.uk; stefan@...er.ch;
> otavio@...ystems.com.br; Leonard Crestez <leonard.crestez@....com>;
> schnitzeltony@...il.com; jan.tuerk@...rion.com; Robin Gong
> <yibin.gong@....com>; linux-pwm@...r.kernel.org;
> devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH V6 2/5] pwm: Add i.MX TPM PWM driver support
> 
> On Tue, Mar 19, 2019 at 06:50:12AM +0000, Anson Huang wrote:
> > i.MX7ULP has TPM(Low Power Timer/Pulse Width Modulation Module)
> > inside, it can support multiple PWM channels, all the channels share
> > same counter and period setting, but each channel can configure its
> > duty and polarity independently.
> >
> > There are several TPM modules in i.MX7ULP, the number of channels in
> > TPM modules are different, it can be read from each TPM module's PARAM
> > register.
> >
> > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > ---
> > Changes since V5:
> > 	- improve commit message body;
> > 	- add period round function;
> > 	- use per channel data for saving channel's private data;
> > 	- improve error message output during probe;
> > 	- improve different period settings by different channels' handling;
> > 	- support #pwm-cells 3 cases.
> > ---
> >  drivers/pwm/Kconfig       |  11 ++
> >  drivers/pwm/Makefile      |   1 +
> >  drivers/pwm/pwm-imx-tpm.c | 463
> > ++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 475 insertions(+)
> >  create mode 100644 drivers/pwm/pwm-imx-tpm.c
> >
> > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index
> > 54f8238..3ea0391 100644
> > --- a/drivers/pwm/Kconfig
> > +++ b/drivers/pwm/Kconfig
> > @@ -210,6 +210,17 @@ config PWM_IMX27
> >  	  To compile this driver as a module, choose M here: the module
> >  	  will be called pwm-imx27.
> >
> > +config PWM_IMX_TPM
> > +	tristate "i.MX TPM PWM support"
> > +	depends on ARCH_MXC || COMPILE_TEST
> > +	depends on HAVE_CLK && HAS_IOMEM
> > +	help
> > +	  Generic PWM framework driver for i.MX7ULP TPM module, TPM's
> full
> > +	  name is Low Power Timer/Pulse Width Modulation Module.
> > +
> > +	  To compile this driver as a module, choose M here: the module
> > +	  will be called pwm-imx-tpm.
> > +
> >  config PWM_JZ4740
> >  	tristate "Ingenic JZ47xx PWM support"
> >  	depends on MACH_INGENIC
> > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index
> > 448825e..c368599 100644
> > --- a/drivers/pwm/Makefile
> > +++ b/drivers/pwm/Makefile
> > @@ -19,6 +19,7 @@ obj-$(CONFIG_PWM_HIBVT)		+= pwm-
> hibvt.o
> >  obj-$(CONFIG_PWM_IMG)		+= pwm-img.o
> >  obj-$(CONFIG_PWM_IMX1)		+= pwm-imx1.o
> >  obj-$(CONFIG_PWM_IMX27)		+= pwm-imx27.o
> > +obj-$(CONFIG_PWM_IMX_TPM)	+= pwm-imx-tpm.o
> >  obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
> >  obj-$(CONFIG_PWM_LP3943)	+= pwm-lp3943.o
> >  obj-$(CONFIG_PWM_LPC18XX_SCT)	+= pwm-lpc18xx-sct.o
> > diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
> new
> > file mode 100644 index 0000000..bb6b27e
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-imx-tpm.c
> > @@ -0,0 +1,463 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright 2018-2019 NXP.
> > + *
> > + * Limitations:
> > + * - The TPM counter and period counter are shared between
> > + *   multiple channels, so all channels should use same period
> > + *   settings.
> > + */
> > +
> > +#include <linux/bitfield.h>
> > +#include <linux/bitops.h>
> > +#include <linux/clk.h>
> > +#include <linux/err.h>
> > +#include <linux/io.h>
> > +#include <linux/log2.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/of_address.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pwm.h>
> > +#include <linux/slab.h>
> > +
> > +#define PWM_IMX_TPM_PARAM	0x4
> > +#define PWM_IMX_TPM_GLOBAL	0x8
> > +#define PWM_IMX_TPM_SC		0x10
> > +#define PWM_IMX_TPM_CNT		0x14
> > +#define PWM_IMX_TPM_MOD		0x18
> > +#define PWM_IMX_TPM_CnSC(n)	(0x20 + (n) * 0x8)
> > +#define PWM_IMX_TPM_CnV(n)	(0x24 + (n) * 0x8)
> > +
> > +#define PWM_IMX_TPM_PARAM_CHAN			GENMASK(7,
> 0)
> > +
> > +#define PWM_IMX_TPM_SC_PS			GENMASK(2, 0)
> > +#define PWM_IMX_TPM_SC_CMOD			GENMASK(4, 3)
> > +#define PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK	BIT(3)
> > +#define PWM_IMX_TPM_SC_CPWMS			BIT(5)
> > +
> > +#define PWM_IMX_TPM_CnSC_CHF	BIT(7)
> > +#define PWM_IMX_TPM_CnSC_MSB	BIT(5)
> > +#define PWM_IMX_TPM_CnSC_MSA	BIT(4)
> > +#define PWM_IMX_TPM_CnSC_ELS	GENMASK(3, 2) /* combine ELSA and
> ELSB as a field */
> 
> I'd write a more verbose comment here to make this understandable.
> Something like:
> 
> /*
>  * The reference manual describes this field as two separate bits. The
>  * samantic of the two bits isn't orthogonal though, so they are treated
>  * together as a 2-bit field here.
>  */

OK.

> 
> > +
> > +#define PWM_IMX_TPM_MOD_MOD	GENMASK(15, 0)
> > +
> > +#define PWM_IMX_TPM_MAX_COUNT		0xffff
> 
> This is just the maximal value for PWM_IMX_TPM_MOD_MOD? If so, this
> should be reflected in the name. Other than that,
> PWM_IMX_TPM_MOD_MOD could be used for that, too.

I think I can just use PWM_IMX_TPM_MOD_MOD directly, as this is indicating
MAX period count.

> 
> > +struct imx_tpm_pwm_chip {
> > +	struct pwm_chip chip;
> > +	struct clk *clk;
> > +	void __iomem *base;
> > +	struct mutex lock;
> > +	u32 user_count;
> > +	u32 enable_count;
> > +	u32 real_period;
> > +};
> > +
> > +struct imx_tpm_pwm_channel {
> > +	u32 config;
> > +	bool status;
> > +};
> > +
> > +static inline struct imx_tpm_pwm_chip *to_imx_tpm_pwm_chip(struct
> > +pwm_chip *chip) {
> > +	return container_of(chip, struct imx_tpm_pwm_chip, chip); }
> > +
> > +static unsigned int pwm_imx_tpm_round_period(struct pwm_chip *chip,
> > +					     u32 period)
> > +{
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +	u32 rate, real_period, prescale, period_count;
> > +	u64 tmp;
> > +
> > +	rate = clk_get_rate(tpm->clk);
> > +	tmp = period;
> > +	tmp *= rate;
> > +	tmp = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
> 
> The value tmp holds is the time a single counter step takes, right?
> Please give that a better name. Something like clock_unit.

OK.

> 
> > +	if (tmp <= PWM_IMX_TPM_MAX_COUNT) {
> > +		prescale = 0;
> > +	} else {
> > +		prescale = roundup_pow_of_two(tmp /
> > +					      (PWM_IMX_TPM_MAX_COUNT +
> 1));
> 
> Do divide a u64 you must not use a plain division. You need div64_ul() here.
> 
> > +		prescale = ilog2(prescale);
> 
> This is equivalent to:
> 
> 	prescale = roundup_pow_of_two(tmp);
> 	prescale = ilog2(prescale) - 16;
> 
> which safes a division. (Of course don't use a plain 16 in your code.)
> 

OK, I was just using tmp as a temp value which can be used in following,
Now that it is NOT a good way, I will optimize it following your advices.

> > +	}
> > +
> > +	/* if no valid prescale found, use MAX instead */
> > +	if ((!FIELD_FIT(PWM_IMX_TPM_SC_PS, prescale)))
> > +		prescale = PWM_IMX_TPM_SC_PS >>
> __bf_shf(PWM_IMX_TPM_SC_PS);
> 
> 		prescale = FIELD_PREP(PWM_IMX_TPM_SC_PS,
> PWM_IMX_TPM_SC_PS)
> 
> What is the consequence if the calculated prescale isn't valid? I assume this
> yields a greatly different period? If yes, this should result in an error.

Yes, that is what I intend to do, if a request period is too large and the prescale
Can NOT meet the requirement, I force it to the largest value that hardware can
Provide, I am NOT sure if it is the correct solution, if no, I can make it return error
If round period returns an invalid result.

> 
> > +	/* if no valid period count found, use MAX instead */
> > +	period_count = (tmp + ((1 << prescale) >> 1)) >> prescale;
> > +	if (period_count > PWM_IMX_TPM_MOD_MOD)
> > +		period_count = PWM_IMX_TPM_MOD_MOD;
> 
> Ditto.
> 
> > +	/* calculate real period HW can support */
> > +	tmp = period_count;
> > +	tmp *= (1 << prescale) * NSEC_PER_SEC;
> 
> I don't know what the compiler does here, I guess it is a bit easier for it to
> optimise here if you write:
> 
> 	tmp = (u64)period_count << prescale;
> 	tmp *= NSEC_PER_SEC;


OK, I just don't want to use (u64) force cast, so I did that.

> 
> > +	real_period = DIV_ROUND_CLOSEST_ULL(tmp, rate);
> > +
> > +	return real_period;
> > +}
> > +
> > +static void pwm_imx_tpm_config_counter(struct pwm_chip *chip, u32
> > +period) {
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +	u32 val, rate, prescale, saved_cmod;
> > +	u64 tmp;
> > +
> > +	rate = clk_get_rate(tpm->clk);
> > +	tmp = period;
> > +	tmp *= rate;
> > +	tmp = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
> > +	if (tmp <= PWM_IMX_TPM_MAX_COUNT) {
> > +		prescale = 0;
> > +	} else {
> > +		prescale = roundup_pow_of_two(tmp /
> > +					      (PWM_IMX_TPM_MAX_COUNT +
> 1));
> > +		prescale = ilog2(prescale);
> > +	}
> > +
> > +	/* make sure counter is disabled for programming prescale */
> > +	val = readl(tpm->base + PWM_IMX_TPM_SC);
> > +	saved_cmod = FIELD_GET(PWM_IMX_TPM_SC_CMOD, val);
> > +	if (saved_cmod) {
> > +		val &= ~PWM_IMX_TPM_SC_CMOD;
> > +		writel(val, tpm->base + PWM_IMX_TPM_SC);
> > +	}
> > +
> > +	/* set TPM counter prescale */
> > +	val = readl(tpm->base + PWM_IMX_TPM_SC);
> > +	val &= ~PWM_IMX_TPM_SC_PS;
> > +	val |= FIELD_PREP(PWM_IMX_TPM_SC_PS, prescale);
> > +	writel(val, tpm->base + PWM_IMX_TPM_SC);
> > +
> > +	/*
> > +	 * set period count: according to RM, the MOD register is
> > +	 * updated immediately after CMOD[1:0] = 2b'00 above
> > +	 */
> > +	val = (tmp + ((1 << prescale) >> 1)) >> prescale;
> > +	writel(val, tpm->base + PWM_IMX_TPM_MOD);
> > +
> > +	/* restore the clock mode if necessary */
> > +	if (saved_cmod) {
> > +		val = readl(tpm->base + PWM_IMX_TPM_SC);
> > +		val |= FIELD_PREP(PWM_IMX_TPM_SC_CMOD, saved_cmod);
> > +		writel(val, tpm->base + PWM_IMX_TPM_SC);
> > +	}
> > +
> > +	tpm->real_period = period;
> > +}
> > +
> > +static void pwm_imx_tpm_config(struct pwm_chip *chip,
> > +			       struct pwm_device *pwm,
> > +			       u32 period,
> > +			       u32 duty_cycle,
> > +			       enum pwm_polarity polarity) {
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +	struct imx_tpm_pwm_channel *chan = pwm_get_chip_data(pwm);
> > +	u32 val;
> > +	u64 tmp;
> > +
> > +	/* set duty counter */
> > +	tmp = readl(tpm->base + PWM_IMX_TPM_MOD) &
> PWM_IMX_TPM_MOD_MOD;
> > +	tmp *= duty_cycle;
> > +	val = DIV_ROUND_CLOSEST_ULL(tmp, period);
> > +	writel(val, tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm));
> > +
> > +	/*
> > +	 * set polarity (for edge-aligned PWM modes)
> > +	 *
> > +	 * ELS[1:0] = 2b10 yields normal polarity behaviour,
> > +	 * ELS[1:0] = 2b01 yields inversed polarity.
> > +	 * The other values are reserved.
> > +	 */
> > +	val = readl(tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
> > +	val &= ~(PWM_IMX_TPM_CnSC_ELS | PWM_IMX_TPM_CnSC_MSA);
> > +	val |= PWM_IMX_TPM_CnSC_MSB;
> > +	val |= (polarity == PWM_POLARITY_NORMAL) ?
> > +		FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 0x2) :
> > +		FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 0x1);
> > +	/*
> > +	 * polarity settings will enabled/disable output status
> > +	 * immediately, so here ONLY save the config and write
> > +	 * it into register when channel is enabled/disabled.
> > +	 */
> > +	chan->config = val;
> 
> This function's behaviour is strange. It configures the hardware with the right
> the duty_cycle but not the polarity. I cannot imagine that this not buggy.

I think that is hardware limitation here, I used the polarity setting to enable/disable
the channel, if we set the polarity here directly, the output status may NOT reflect
the real state, if eventually the status is disabled, setting the polarity directly into register
will make the output active, that is NOT expected, right? And that is why I put comments
here.

> 
> > +}
> > +
> > +/*
> > + * When a channel's polarity is configured, the polarity settings
> > + * will be saved and ONLY write into the register when the channel
> > + * is enabled.
> > + *
> > + * When a channel is disabled, its polarity settings will be saved
> > + * and its output will be disabled by clearing polarity settings.
> > + *
> > + * When a channel is enabled, its polarity settings will be restored
> > + * and output will be enabled again.
> > + */
> > +static void pwm_imx_tpm_enable(struct pwm_chip *chip,
> > +			       struct pwm_device *pwm,
> > +			       bool enable)
> > +{
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +	struct imx_tpm_pwm_channel *chan = pwm_get_chip_data(pwm);
> > +	u32 val;
> > +
> > +	val = readl(tpm->base + PWM_IMX_TPM_SC);
> > +	if (enable) {
> > +		/* restore channel config */
> > +		writel(chan->config,
> > +		       tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
> > +
> > +		if (++tpm->enable_count == 1) {
> > +			/* start TPM counter */
> > +			val |= PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK;
> > +			writel(val, tpm->base + PWM_IMX_TPM_SC);
> > +		}
> > +	} else {
> > +		/* disable channel */
> > +		val = readl(tpm->base + PWM_IMX_TPM_CnSC(pwm-
> >hwpwm));
> > +		val &= ~(PWM_IMX_TPM_CnSC_MSA |
> PWM_IMX_TPM_CnSC_MSB |
> > +			 PWM_IMX_TPM_CnSC_ELS);
> > +		writel(val, tpm->base + PWM_IMX_TPM_CnSC(pwm-
> >hwpwm));
> > +
> > +		if (--tpm->enable_count == 0) {
> > +			/* stop TPM counter since all channels are disabled
> */
> > +			val &= ~PWM_IMX_TPM_SC_CMOD;
> > +			writel(val, tpm->base + PWM_IMX_TPM_SC);
> > +		}
> > +	}
> > +
> > +	/* update channel status */
> > +	chan->status = enable;
> > +}
> > +
> > +static void pwm_imx_tpm_get_state(struct pwm_chip *chip,
> > +				  struct pwm_device *pwm,
> > +				  struct pwm_state *state)
> > +{
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +	u32 rate, val;
> > +	u64 tmp;
> > +
> > +	/* get period */
> > +	state->period = tpm->real_period;
> > +
> > +	/* get duty cycle */
> > +	rate = clk_get_rate(tpm->clk);
> > +	val = readl(tpm->base + PWM_IMX_TPM_SC);
> > +	val = FIELD_GET(PWM_IMX_TPM_SC_PS, val);
> > +	tmp = readl(tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm));
> > +	tmp *= (1 << val) * NSEC_PER_SEC;
> > +	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate);
> > +
> > +	/* get polarity */
> > +	val = readl(tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
> > +	if (FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val) == 0x1)
> > +		state->polarity = PWM_POLARITY_INVERSED;
> > +	else if (FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val) == 0x2)
> > +		state->polarity = PWM_POLARITY_NORMAL;
> 
> 	else ?

OK, maybe I can set other values to a default polarity.

> 
> > +
> > +	/* get channel status */
> > +	state->enabled = FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val) ? true :
> > +false; }
> > +
> > +static int pwm_imx_tpm_apply(struct pwm_chip *chip, struct pwm_device
> *pwm,
> > +			     struct pwm_state *state)
> > +{
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +	struct imx_tpm_pwm_channel *chan = pwm_get_chip_data(pwm);
> > +	u32 p;
> > +
> > +	mutex_lock(&tpm->lock);
> > +
> > +	if (state->period != tpm->real_period) {
> > +		/*
> > +		 * TPM counter is shared by multiple channels, so
> > +		 * prescale and period can NOT be modified when
> > +		 * there are multiple channels in use with different
> > +		 * period settings.
> > +		 */
> > +		p = pwm_imx_tpm_round_period(chip, state->period);
> > +		if (p != tpm->real_period && tpm->user_count != 1)
> > +			return -EBUSY;
> > +		else if (p != tpm->real_period)
> > +			pwm_imx_tpm_config_counter(chip, p);
> > +	}
> 
> This looks more complicated than it should be. What about:
> 
> 	p = pwm_imx_tpm_round_period(chip, state->period);
> 
> 	if (p != tpm->real_period) {
> 		if (tpm->user_count != 1)
> 			return -EBUSY;
> 
> 		pwm_imx_tpm_config_counter(chip, p);
> 	}
> 
> Another optimisation is possible here as pwm_imx_tpm_round_period and
> pwm_imx_tpm_config_counter do effectively the same calculations: Let
> pwm_imx_tpm_round_period return the respective register values that are
> then just written to the registers instead of recalculating them once more.
> 

This is also my original thoughts, it can avoid computing again in config function, but
I have to find a place to save the prescale and period count, maybe adding them in
driver data? Then in config function, just write the registers directly.


> > +	if (state->enabled == false) {
> > +		/*
> > +		 * if eventually the PWM output is LOW, either
> > +		 * duty cycle is 0 or status is disabled, need
> > +		 * to make sure the output pin is LOW.
> > +		 */
> > +		pwm_imx_tpm_config(chip, pwm, state->period,
> > +				   0, state->polarity);
> > +		if (chan->status == true)
> > +			pwm_imx_tpm_enable(chip, pwm, false);
> > +	} else {
> > +		pwm_imx_tpm_config(chip, pwm, state->period,
> > +				   state->duty_cycle, state->polarity);
> > +		if (chan->status == false)
> > +			pwm_imx_tpm_enable(chip, pwm, true);
> > +	}
> 
> This function is really hard to understand. The factors making this
> complicated are:
> 
>  - Strange semantic of pwm_imx_tpm_config, IMHO the things done in both
>    pwm_imx_tpm_config and pwm_imx_tpm_enable should be done in a
> single
>    function.
>  - "status" could better be names "enabled"
> 
> IMHO it should look like:
> 
> 	int my_apply(chip, pwm, state)
> 	{
> 		ret = my_round_state(state, &hwparams);
> 		if (ret)
> 			return ret;
> 
> 		mutex_lock();
> 
> 		if (usercount > 1 &&
> 		    my_hwparams_interfere(current_state, hwparams))
> 			ret = -EBUSY;
> 			goto out_unlock;
> 
> 		my_apply_to_hardware(hwparams);
> 
> 		mutex_unlock();
> 	out_unlock:
> 
> 		return ret;
> 	}
> 

Agreed, that can also solve the polarity setting question, will give it a try.

> > +	mutex_unlock(&tpm->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static int pwm_imx_tpm_request(struct pwm_chip *chip, struct
> > +pwm_device *pwm) {
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +	struct imx_tpm_pwm_channel *chan;
> > +
> > +	chan = devm_kzalloc(chip->dev, sizeof(*chan), GFP_KERNEL);
> > +	if (!chan)
> > +		return -ENOMEM;
> > +
> > +	pwm_set_chip_data(pwm, chan);
> > +
> > +	mutex_lock(&tpm->lock);
> > +	tpm->user_count++;
> > +	mutex_unlock(&tpm->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static void pwm_imx_tpm_free(struct pwm_chip *chip, struct
> pwm_device
> > +*pwm) {
> > +	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
> > +
> > +	mutex_lock(&tpm->lock);
> > +	tpm->user_count--;
> > +	mutex_unlock(&tpm->lock);
> > +
> > +	devm_kfree(chip->dev, pwm_get_chip_data(pwm));
> > +	pwm_set_chip_data(pwm, NULL);
> > +}
> > +
> > +static const struct pwm_ops imx_tpm_pwm_ops = {
> > +	.request = pwm_imx_tpm_request,
> > +	.free = pwm_imx_tpm_free,
> > +	.get_state = pwm_imx_tpm_get_state,
> > +	.apply = pwm_imx_tpm_apply,
> > +	.owner = THIS_MODULE,
> > +};
> > +
> > +static int pwm_imx_tpm_probe(struct platform_device *pdev) {
> > +	struct imx_tpm_pwm_chip *tpm;
> > +	int ret;
> > +	u32 val;
> > +
> > +	tpm = devm_kzalloc(&pdev->dev, sizeof(*tpm), GFP_KERNEL);
> > +	if (!tpm)
> > +		return -ENOMEM;
> > +
> > +	platform_set_drvdata(pdev, tpm);
> > +
> > +	tpm->base = devm_platform_ioremap_resource(pdev, 0);
> > +	if (IS_ERR(tpm->base))
> > +		return PTR_ERR(tpm->base);
> > +
> > +	tpm->clk = devm_clk_get(&pdev->dev, NULL);
> > +	if (IS_ERR(tpm->clk)) {
> > +		ret = PTR_ERR(tpm->clk);
> > +		if (ret != -EPROBE_DEFER)
> > +			dev_err(&pdev->dev,
> > +				"failed to get PWM clock: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	ret = clk_prepare_enable(tpm->clk);
> > +	if (ret) {
> > +		dev_err(&pdev->dev,
> > +			"failed to prepare or enable clock: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	tpm->chip.dev = &pdev->dev;
> > +	tpm->chip.ops = &imx_tpm_pwm_ops;
> > +	tpm->chip.base = -1;
> > +	tpm->chip.of_xlate = of_pwm_xlate_with_flags;
> > +	tpm->chip.of_pwm_n_cells = 3;
> > +
> > +	/* get number of channels */
> > +	val = readl(tpm->base + PWM_IMX_TPM_PARAM);
> > +	tpm->chip.npwm = FIELD_GET(PWM_IMX_TPM_PARAM_CHAN, val);
> > +
> > +	mutex_init(&tpm->lock);
> > +
> > +	ret = pwmchip_add(&tpm->chip);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
> > +		clk_disable_unprepare(tpm->clk);
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static int pwm_imx_tpm_remove(struct platform_device *pdev) {
> > +	struct imx_tpm_pwm_chip *tpm = platform_get_drvdata(pdev);
> > +	int ret = pwmchip_remove(&tpm->chip);
> > +
> > +	clk_disable_unprepare(tpm->clk);
> > +
> > +	return ret;
> > +}
> > +
> > +static int __maybe_unused pwm_imx_tpm_suspend(struct device *dev) {
> > +	struct imx_tpm_pwm_chip *tpm = dev_get_drvdata(dev);
> > +
> > +	if (tpm->enable_count == 0)
> > +		clk_disable_unprepare(tpm->clk);
> > +
> > +	return 0;
> 
> IMHO you should return an error if enable_count isn't 0 to prevent going to
> suspend.

OK, although maybe there is other voice that fail to disabling a clock does NOT impact
System suspend function, the clock will be automatically turned off by hardware anyway,
But I agree that adding error return is also making sense here.

Anson.

> 
> > +}
> > +
> > +static int __maybe_unused pwm_imx_tpm_resume(struct device *dev) {
> > +	struct imx_tpm_pwm_chip *tpm = dev_get_drvdata(dev);
> > +	int ret = 0;
> > +
> > +	if (tpm->enable_count == 0) {
> > +		ret = clk_prepare_enable(tpm->clk);
> > +		if (ret)
> > +			dev_err(dev,
> > +				"failed to prepare or enable clock: %d\n",
> > +				ret);
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static SIMPLE_DEV_PM_OPS(imx_tpm_pwm_pm,
> > +			 pwm_imx_tpm_suspend, pwm_imx_tpm_resume);
> > +
> > +static const struct of_device_id imx_tpm_pwm_dt_ids[] = {
> > +	{ .compatible = "fsl,imx-tpm", },
> > +	{ /* sentinel */ }
> > +};
> > +MODULE_DEVICE_TABLE(of, imx_tpm_pwm_dt_ids);
> > +
> > +static struct platform_driver imx_tpm_pwm_driver = {
> > +	.driver = {
> > +		.name = "imx-tpm-pwm",
> > +		.of_match_table = imx_tpm_pwm_dt_ids,
> > +		.pm = &imx_tpm_pwm_pm,
> > +	},
> > +	.probe	= pwm_imx_tpm_probe,
> > +	.remove = pwm_imx_tpm_remove,
> > +};
> > +module_platform_driver(imx_tpm_pwm_driver);
> > +
> > +MODULE_AUTHOR("Anson Huang <Anson.Huang@....com>");
> > +MODULE_DESCRIPTION("i.MX TPM PWM Driver"); MODULE_LICENSE("GPL
> v2");
> 
> Best regards
> Uwe
> 
> --
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 |
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