Re: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

Re: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Tomasz Figa]

On Thursday 22 of August 2013 09:52:42 Xiubo Li-B47053 wrote:
> Hi Tomasz,
> 
> > > > If the meaning of flags cell is the same as in generic, default PWM
> > > > specifier format, then it should be noted here and generic PWM
> > > > binding documentation mentioned.
> > > 
> > > OK, How about the following ?
> > > - #pwm-cells: Should be 3. See pwm.txt in this directory for a
> > > 
> > >   description of the cells format.
> > 
> > I meant just the last cell, which stores flags, but actually this might
> > be a good idea, but with slightly extended description. Something among
> > those
> > 
> > lines:
> >  - #pwm-cells: Should be 3. The default three cell format specified by
> > 
> > generic PWM bindings are used. Refer to the documentation of generic
> > PWM
> > bindings for more information about the meaning of cells.
> 
> That's perfect.

OK.

> > > > > +- fsl,pwm-clk-ps: the ftm0 pwm clock's prescaler,
> > > > > divide-by 2^n(n = 0 ~ 7).
> > > > 
> > > > Is it a hardware-specific property?
> > > 
> > > Yes, I will revise it in v2.
> > 
> > I'd like to hear a bit more elaborate description of this property.
> > What
> > are the factors that decide what value should be used here?
> 
> Sorry, "the ftm0 pwm clock's prescaler" maybe also confuse you, it should
> be "the ftm pwm counter clock input prescaler".
> 
> The ftm's counter clock can be selected as :
> System clock,
> Fixed frequency clock,
> External clock.
> 
> And the ftm module clock has only system clock source.
> 
> The fixed frequency clock is an alternative clock source for the FTM
> counter that allows the selection of a clock other than the system clock
> or an external clock. This clock input is defined by chip integration.
> Due to FTM hardware implementation limitations, the frequency of the
> fixed frequency clock must not exceed 1/2 of the system clock frequency.
> 
> The external clock passes through a synchronizer clocked by the system
> clock to assure that counter transitions are properly aligned to system
> clock transitions.Therefore, to meet Nyquist criteria considering also
> jitter, the frequency of the external clock source must not exceed 1/4
> of the system clock frequency.
> 
> So, if the fixed frequency clock or external clock equal or exceed the
> system clock...

Can't the driver check the frequency of fixed or external clock and 
calculate optimal divisor value so that it is less than 1/4 of system clock 
frequency?

> > > > > +- fsl,pwm-number: the number of PWM devices, and is must equal
> > > > > to
> > > > > the
> > > > > number +  of "fsl,pwm-channels".
> > > > 
> > > > This is redundant, because you can simply count how many entries
> > > > have been specified in fsl,pwm-channels.
> > > 
> > > Yes, I will revise it in v2.
> > > And this would be renamed to " fsl,pwm-channel-number", which can be
> > > more Readable and understood.
> > 
> > I meant that you don't need to specify how many entries other property
> > has in another property, because device tree provides information about
> > sizes of all properties. So, in parsing code, you would be able to
> > simply get the size of "fsl,pwm-channels" property in bytes, divide
> > that by sizeof(u32) and get the numer of cells specified.
> 
> OK, I will revise it in v2.

As I noted below, it won't be needed anymore. I just commented on this as a 
side note.

> > > > > +- fsl,pwm-channels: the channels' order which is be used for pwm
> > > > > +in
> > > > > ftm0 +  module, and they must be one or some of 0 ~ 7, because
> > > > > the
> > > > > ftm0 only has +  8 channels can be used.
> > > > 
> > > > Could you explain meaning of this property more precisely? I'm
> > > > interested especially how is this related to the PWM IP block and
> > > > boards.
> > > 
> > > Yes.
> > > There are 8 channels most. While the pinctrls of 4th and 5th channels
> > > could be used by uart's Rx and Tx, then these 2 channels won't be
> > > used
> > > for pwm output, so there will be 6 channels available by the pwm.
> > > Thus, the pwm chip will register only 6 pwms(6 channels)
> > > most("fsl,pwm-channel-orders = {0 1 2 3 6 7}").And also the
> > > "fsl,pwm-channel-number" will be 6.
> > > 
> > > If hasn't any other problems, I will revise It in v2.
> > > And this will be renamed to "fsl,pwm-channel-orders", which can be
> > > more readable and understood.
> > 
> > As Sascha Hauer already suggested, you could get rid of both this and
> > "fsl,pwm-channel-number" properties and simply register all the
> > channels. This way you will have a deterministic 1:1 mapping of real
> > hardware channels to channels specified in device tree, which is
> > definitely the way to go.
> > 
> > Now as a safety measure, you could simply move the specification of
> > pinctrl states from SoC family or SoC level dtsi file to board level
> > dts, where only pinctrl states of channels used by a particular board
> > would be specified, so nothing could break operation of other devices
> > that share pin muxes with remaining channels.
> 
> Yes, I was also considering it, but not very be clear yet.
> Thanks very much for your and Sascha's help.
> I will try to implement it in v2.

OK, good.

Best regards,
Tomasz

RE: [PATCH 2/4] ARM: dts: Add Freescale ftm pwm node for VF610.

[Xiubo Li-B47053]

Hi Thierry,


> Subject: Re: [PATCH 2/4] ARM: dts: Add Freescale ftm pwm node for VF610.
> 
> On Wed, Aug 21, 2013 at 11:07:40AM +0800, Xiubo Li wrote:
> > Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
> > ---
> >  arch/arm/boot/dts/vf610.dtsi | 83
> > +++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 82 insertions(+), 1 deletion(-)
> 
> Please also pay attention to the correct capitalization in the subject
> here. "FTM" and "PWM". Furthermore this could probably use more than a
> single line as patch description.
> 

Yes, I will revise it in v2.



Thanks very much.

--
Best Regards.
Xiubo

RE: [PATCH 3/4] ARM: dts: Enables ftm pwm device for Vybrid VF610 TOWER board.

[Xiubo Li-B47053]

Hi Thierry,


> Subject: Re: [PATCH 3/4] ARM: dts: Enables ftm pwm device for Vybrid
> VF610 TOWER board.
> 
> On Wed, Aug 21, 2013 at 11:07:41AM +0800, Xiubo Li wrote:
> > Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
> > ---
> >  arch/arm/boot/dts/vf610-twr.dts | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> 
> Same comments as for patch 2/4.
> 

Yes, I will revise it then.


Thanks very much.

--
Best Regards.
Xiubo

RE: [PATCH 1/4] pwm: add freescale ftm pwm driver support

[Xiubo Li-B47053]

Hi Thierry,

See the comments below.


> I think the correct capitalizations are: "Freescale", "FTM" and "PWM".
> There are other occurrences in the rest of the driver that I haven't
> explicitly pointed out.
> 

Yes, that's much better.


> > +config PWM_FTM
> 
> Perhaps name this PWM_FSL_FTM to match the driver name?
> 

OK.


> And fix this up to be "pwm-fsl-ftm".

Yes, I will.


> > +#define FTM_CSC_BASE        0x0C
> > +#define FTM_CSC(_CHANNEL) \
> > +	(FTM_CSC_BASE + (_CHANNEL * 0x08))
> 
> I prefer lowercase variables in macros:
> 
> 	#define FTM_CSC(channel) \
> 		(FTM_CSC_BASE + (channel * 8))
> 
Yes, That's better.


> > +#define FTM_PWMMODE         (FTMCnSC_MSB)
> > +#define FTM_HIGH_TRUE       (FTMCnSC_ELSB)
> > +#define FTM_LOW_TRUE        (FTMCnSC_ELSA)
> 
> What's the reason for redefining these? Can't you just use the FTMCnSC_*
> defines directly?
> 

Just for more readable and comprehension.
I will revise it by not losing above two key elements. 

> > +#define FTM_CV(_CHANNEL) \
> > +	(FTM_CV_BASE + (_CHANNEL * 0x08))
> 
> Same comment as for FTM_CSC above.
>

Yes.
 
> > +#define FTM_MAX_CHANNEL     0x08
> 
> There should be no need for this. The only place where you use this is
> when assigning it to pwm_chip.npwm, so you may as well use the literal
> there.
> 

I have recoded the driver, and the macro is used more than one time now.


> > +	struct platform_device *pdev;
> 
> You never use this platform_device. And you have to assign &pdev->dev to
> the pwm_chip.dev anyway, so why not just use that consistently and drop
> the pdev field?
>

Yes, I have droped the pdev field now.
 

> > +	unsigned int	cpwm;
> > +	struct fsl_pwm fpwms[FTM_MAX_CHANNEL];
> 
> Please don't do this. Use pwm_set_chip_data()/pwm_get_chip_data() to
> associate per-channel specific data.
>

I have replaced them now.
 
> > +	/* pinctrl handles */
> 
> Nit: it's only a single handle.
> 

Yes.

> > +	struct pinctrl          *pinctrl;
> 
> You also use tabs and spaces inconsistently here. I suggest you use a
> single space between the data type and the field name, that way it's much
> easier to stay consistent.
> 

Now I have revised all about this.

> > +static int fsl_pwm_request_channel(struct pwm_chip *chip,
> > +			       struct pwm_device *pwm)
> 
> The arguments on the trailing line aren't properly aligned. They should
> be aligned with the arguments on the first line.
> 

The same as the above comment.


> > +	ret = clk_prepare_enable(fpc->clk);
> 
> This should probably be just clk_prepare(). Or is there some reason why
> you can't delay clk_enable() to the .enable() operation?
> 

Firstly, we should be clear that the fpc->clk is chip's work clock.
If so, after the .request() is called and before .enable() is called, the custumer will call .config(), 
in which will read/write the pwm chip registers, if the module clock is still disabled, then the system will hang up.


> > +static int fsl_updata_config(struct fsl_pwm_chip *fpc,
> > +			     struct pwm_device *pwm)
> 
> Parameter alignment again. Please also check all other functions.
> 

Yes, I have revise all about this.

> > +{
> > +	int i;
> 
> This should be unsigned int.
> 

I will revise it.

> > +static unsigned long
> > +fsl_rate_to_cycles(struct fsl_pwm_chip *fpc, int time_ns)
> 
> The above two lines are 78 characters when joined, so there's no need to
> split them.
> 

OK, I have revise all about this.

> Perhaps time_ns should be "unsigned long"?
> 

Shouldn't this be same with "int duty_ns" and "int period_ns", which are defined by 
struct pwm_ops {
...
	int (*config)(struct pwm_chip *chip,
                    struct pwm_device *pwm,
                    int duty_ns, int period_ns);
...
}  ?


> > +	ps = (0x01 << fpc->clk_ps);
> 
> This is fairly short, so you could do it along with the variable
> declaration. Also there's no need for the parentheses or the hexadecimal
> prefix (0x01 == 1):
> 
> 	unsigned long ps = 1 << fpc->clk_ps;
> 

OK, I will revise it then.

> > +	/* The module clk is HZ/s, the time_ns parameter
> > +	 * is based nanosecond, so here should divide
> > +	 * 1000000000UL.
> > +	 */
> 
> Block comments should be:
> 
> 	/*
> 	 * ...
> 	 * ...
> 	 */
> 
> Also HZ/s isn't a valid unit for a clock frequency. And time_ns also has
> the _ns suffix to designate the unit, so as a whole that comment doesn't
> add any real information and can just as well be dropped.
> 

I will revise it.

> > +static int fsl_pwm_config_channel(struct pwm_chip *chip,
> 
> I think you can safely drop the _channel suffix from the PWM operations.
> 

By adding _channel suffix just for more comprehensave about the pwm's muti-channel operation.
If this is redundant here, I will drop it.


> > +	fpc = to_fsl_chip(chip);
> > +
> > +	if (WARN_ON(!test_bit(PWMF_REQUESTED, &pwm->flags)))
> > +		return -ESHUTDOWN;
> 
> Erm... how do you think this could ever happen? Users need to request a
> PWM to obtain a struct pwm_device, in which case PWMF_REQUESTED will
> always be set. There are a few other occurrences throughout the rest of
> the driver that I haven't pointed out explicitly.
> 

Does the following case is exist ?
The customer in one thread has .free(pwm_1), while in another thread, 
which maybe had slept in for some reason, will call .config/.enable/.disable?

If so, as I have explained before, if the pwm_1 has been freed, the module clock maybe
disabled too, so if the .config is call the system will hang up.



> > +	fpc->fpwms[pwm->hwpwm].period_cycles = period_cycles;
> > +	fpc->fpwms[pwm->hwpwm].duty_cycles = duty_cycles;
> 
> You use these for the sole purpose of passing them into the
> fsl_updata_config() function, so I wonder why you can't just pass them as
> parameters and get rid of struct fsl_pwm as a bonus?
> 

Before I think the fpc has all the information the fsl_update_config() function needed.

Now, I have dropt the fsl_update_config() function.


> > +	fsl_updata_config(fpc, pwm);
> 
> And now that I think about it: perhaps this was supposed to be called
> fsl_update_config() instead of fsl_updat*a*_config()?
> 
Well, a written mistake.


> > +	reg &= ~(0x01 << pwm->hwpwm);
> 
> This would be slightly more canonical as:
> 
> 	reg &= ~BIT(pwm->hwpwm);
> 

Yes, looks much better.

> > +	reg |= (polarity << pwm->hwpwm);
> 
> And perhaps here it would be better to be explicit. I think it's unlikely
> that enum pwm_polarity will even gain a third entry, but better be safe
> than sorry:
> 
> 	if (polarity == PWM_POLARITY_INVERSED)
> 		reg |= BIT(pwm->hwpwm);
> 	else
> 		reg &= ~BIT(pwm->hwpwm);
> 

I will think it over.
While only the polarity's bit0 is used for polarity's statement. If other bit won't has any other
meaning and purpose in the feature, I will replace it derictly.

> > +static int is_any_other_channel_enabled(struct pwm_chip *chip,
> > +				    unsigned int cur)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < chip->npwm; i++) {
> > +		if (i == cur)
> > +			continue;
> > +		if (test_bit(PWMF_ENABLED, &chip->pwms[i].flags))
> > +			return 1;
> > +	}
> > +
> > +	return 0;
> > +}
> 
> This can probably be better done using a reference/enable count. Instead
> of having to iterate over all PWM channels of the chip and checking their
> flags, just keep track of how many times .enable() and .disable() are
> called.
> 
> To make it easier you can probably wrap that into two functions, such as
> fsl_clock_enable() and fsl_clock_disable().
> 
> > +static int fsl_pwm_enable_channel(struct pwm_chip *chip,
> > +			      struct pwm_device *pwm)
> > +{
> [...]
> > +	if (is_any_other_channel_enabled(chip, pwm->hwpwm))
> > +		return 0;
> 
> This is where you'd call fsl_clock_enable()...
> 
> > +	reg = readl(fpc->base + FTM_SC);
> > +	reg &= ~((FTMSC_CLK_MASK << FTMSC_CLK_OFFSET) |
> > +			(FTMSC_PS_MASK << FTMSC_PS_OFFSET));
> > +	/* select system clock source */
> > +	reg |= (FTMSC_CLKSYS | fpc->clk_ps);
> > +	writel(reg, fpc->base + FTM_SC);
> 
> ... and run this code in fsl_clock_enable() if the enable count is 0 to
> select the system clock when the first PWM is enabled.
> 
> > +static void fsl_pwm_disable_channel(struct pwm_chip *chip,
> > +				struct pwm_device *pwm)
> > +{
> [...]
> > +	if (is_any_other_channel_enabled(chip, pwm->hwpwm))
> > +		return;
> 
> Then call fsl_clock_disable() here...
> 
> > +	writel(0xFF, fpc->base + FTM_OUTMASK);
> > +	reg = readl(fpc->base + FTM_SC);
> > +	reg &= ~(FTMSC_CLK_MASK << FTMSC_CLK_OFFSET);
> > +	writel(reg, fpc->base + FTM_SC);
> 
> ... and run this code in fsl_clock_disable() if the enable count reaches
> 0 so that the clock is disabled when no PWM channels remain on.
> 

I will think it over and recode about this.


> > +static int fsl_pwm_parse_dt(struct fsl_pwm_chip *fpc) {
> [...]
> > +	int ret = 0;
> > +	u32 chs[FTM_MAX_CHANNEL];
> > +	struct device_node *np = fpc->pdev->dev.of_node;
> > +
> > +	ret = of_property_read_u32(np, "fsl,pwm-clk-ps",
> > +				   &fpc->clk_ps);
> > +	if (ret < 0) {
> > +		dev_err(&fpc->pdev->dev,
> > +				"failed to get pwm "
> > +				"clk prescaler : %d\n",
> > +				ret);
> 
> Perhaps it's more useful to mention the missing property explicitly in
> the error message:
> 
> 		dev_err(fpc->chip.dev,
> 			"failed to parse \"fsl,pwm-clk-ps\" property: %d\n",
> 			ret);
> 

Whil I think the following is better in code. 
 
 		dev_err(fpc->chip.dev,
 			"failed to parse <fsl,pwm-clk-ps> property: %d\n",
 			ret);



> 
> > +		return ret;
> > +	}
> > +	if (fpc->clk_ps > 7 || fpc->clk_ps < 0)
> 
> clk_ps is unsigned and therefore can't be < 0. And a blank line would be
> useful between the previous line ("}") and this line.
> 

I will revise it.

> > +static int fsl_pwm_probe(struct platform_device *pdev) {
> > +	int ret = 0;
> > +	struct fsl_pwm_chip *fpc;
> > +	struct resource *res;
> > +
> > +	fpc = devm_kzalloc(&pdev->dev, sizeof(*fpc), GFP_KERNEL);
> > +	if (!fpc) {
> > +		dev_err(&pdev->dev,
> > +				"failed to allocate memory\n");
> 
> I don't think that's very useful either. If this should indeed ever fail,
> then the driver core will complain about the probe failing and include
> the error code. Since it's the only location where you return that error
> code you know immediately what went wrong.
> 

Yes, for the devm_kzlloc() have print out the fail reason, this will be redundant.
I have revised all about this.

> > +		return -ENOMEM;
> > +	}
> > +
> > +	mutex_init(&fpc->lock);
> > +
> > +	fpc->pdev = pdev;
> > +
> > +	ret = fsl_pwm_parse_dt(fpc);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	fpc->base = devm_ioremap_resource(&pdev->dev, res);
> > +	if (IS_ERR(fpc->base)) {
> > +		dev_err(&pdev->dev,
> > +				"failed to ioremap() registers\n");
> 
> No need for this error message. devm_ioremap_resource() prints out errors
> already on failure.
> 

The same comment as the last one.

> > +	fpc->chip.dev = &pdev->dev;
> > +	fpc->chip.ops = &fsl_pwm_ops;
> > +	fpc->chip.of_xlate = of_pwm_xlate_with_flags;
> > +	fpc->chip.of_pwm_n_cells = 3;
> > +	fpc->chip.base = -1;
> > +
> > +	ret = pwmchip_add(&fpc->chip);
> > +	if (ret < 0) {
> > +		dev_err(&pdev->dev,
> > +				"failed to add ftm0 pwm chip %d\n",
> > +				ret);
> 
> dev_err() will already include the device name in the error message, so I
> don't think you need the "ftm0" here. Also make sure to use the correct
> capitalization for "PWM". And there is no need to split this over so many
> lines, it all fits on a single line just fine. There are other
> occurrences of this, so please double-check.
> 

Yes.
I have revise all about this.



Thanks very much.

--
Best Regards.
Xiubo

Re: [PATCH 1/4] pwm: add freescale ftm pwm driver support

[Thierry Reding]

[-- Attachment #1: Type: text/plain, Size: 4377 bytes --]

On Mon, Aug 26, 2013 at 07:32:23AM +0000, Xiubo Li-B47053 wrote:
> > > +#define FTM_CSC_BASE        0x0C
> > > +#define FTM_CSC(_CHANNEL) \
> > > +	(FTM_CSC_BASE + (_CHANNEL * 0x08))
> > 
> > I prefer lowercase variables in macros:
> > 
> > 	#define FTM_CSC(channel) \
> > 		(FTM_CSC_BASE + (channel * 8))
> > 
> Yes, That's better.

Actually it should even be:

	#define FTM_CSC(channel) \
		(FTM_CSC_BASE + ((channel) * 8))

Just in case channel ends up being an expression.

> > > +	ret = clk_prepare_enable(fpc->clk);
> > 
> > This should probably be just clk_prepare(). Or is there some reason why
> > you can't delay clk_enable() to the .enable() operation?
> > 
> 
> Firstly, we should be clear that the fpc->clk is chip's work clock.
> If so, after the .request() is called and before .enable() is called, the custumer will call .config(), 
> in which will read/write the pwm chip registers, if the module clock is still disabled, then the system will hang up.

Okay. In that case perhaps the better thing to do is call clk_prepare()
during driver probe and only clk_enable() here.

> > Perhaps time_ns should be "unsigned long"?
> > 
> 
> Shouldn't this be same with "int duty_ns" and "int period_ns", which are defined by 
> struct pwm_ops {
> ...
> 	int (*config)(struct pwm_chip *chip,
>                     struct pwm_device *pwm,
>                     int duty_ns, int period_ns);
> ...
> }  ?

Well, the plan is to eventually make duty_ns and period_ns unsigned int
or unsigned long because negative values don't make any sense for them.
With that in mind I think it makes sense to use the proper type here
now.

> > > +static int fsl_pwm_config_channel(struct pwm_chip *chip,
> > 
> > I think you can safely drop the _channel suffix from the PWM operations.
> > 
> 
> By adding _channel suffix just for more comprehensave about the pwm's muti-channel operation.
> If this is redundant here, I will drop it.

The operations are implicitly per-channel operations. So yes, the
_channel suffix is redundant here.

> > > +	fpc = to_fsl_chip(chip);
> > > +
> > > +	if (WARN_ON(!test_bit(PWMF_REQUESTED, &pwm->flags)))
> > > +		return -ESHUTDOWN;
> > 
> > Erm... how do you think this could ever happen? Users need to request a
> > PWM to obtain a struct pwm_device, in which case PWMF_REQUESTED will
> > always be set. There are a few other occurrences throughout the rest of
> > the driver that I haven't pointed out explicitly.
> > 
> 
> Does the following case is exist ?
> The customer in one thread has .free(pwm_1), while in another thread, 
> which maybe had slept in for some reason, will call .config/.enable/.disable?
> 
> If so, as I have explained before, if the pwm_1 has been freed, the module clock maybe
> disabled too, so if the .config is call the system will hang up.

While the above could possibly happen, there's no way the core could
prevent it. And your explicit test couldn't either. So what usually
happens is that a driver requests a PWM device and then has exclusive
access to it. Any other driver that wants to use the same PWM device
can't because it will get an -EBUSY return.

So in your hypothetical case above, if one driver does stuff like that
with a PWM device then that's a driver bug, not something the PWM core
should be required to handle.

> > > +static int fsl_pwm_parse_dt(struct fsl_pwm_chip *fpc) {
> > [...]
> > > +	int ret = 0;
> > > +	u32 chs[FTM_MAX_CHANNEL];
> > > +	struct device_node *np = fpc->pdev->dev.of_node;
> > > +
> > > +	ret = of_property_read_u32(np, "fsl,pwm-clk-ps",
> > > +				   &fpc->clk_ps);
> > > +	if (ret < 0) {
> > > +		dev_err(&fpc->pdev->dev,
> > > +				"failed to get pwm "
> > > +				"clk prescaler : %d\n",
> > > +				ret);
> > 
> > Perhaps it's more useful to mention the missing property explicitly in
> > the error message:
> > 
> > 		dev_err(fpc->chip.dev,
> > 			"failed to parse \"fsl,pwm-clk-ps\" property: %d\n",
> > 			ret);
> > 
> 
> Whil I think the following is better in code. 
>  
>  		dev_err(fpc->chip.dev,
>  			"failed to parse <fsl,pwm-clk-ps> property: %d\n",
>  			ret);

Why? You're quoting which property failed to parse so you should use the
correct character for quoting, which is either the apostrophe (') or the
quotation mark (").

Thierry

[-- Attachment #2: Type: application/pgp-signature, Size: 836 bytes --]

RE: [PATCH 1/4] pwm: add freescale ftm pwm driver support

[Xiubo Li-B47053]

> Actually it should even be:
> 
> 	#define FTM_CSC(channel) \
> 		(FTM_CSC_BASE + ((channel) * 8))
> 

Well, yes, It should be, as Sascha has comment about this before, I have 
already revise it.


> > Firstly, we should be clear that the fpc->clk is chip's work clock.
> > If so, after the .request() is called and before .enable() is called,
> > the custumer will call .config(), in which will read/write the pwm chip
> registers, if the module clock is still disabled, then the system will
> hang up.
> 
> Okay. In that case perhaps the better thing to do is call clk_prepare()
> during driver probe and only clk_enable() here.
> 

Yes, it is.

> > > Perhaps time_ns should be "unsigned long"?
> > >
> >
> > Shouldn't this be same with "int duty_ns" and "int period_ns", which
> > are defined by struct pwm_ops { ...
> > 	int (*config)(struct pwm_chip *chip,
> >                     struct pwm_device *pwm,
> >                     int duty_ns, int period_ns); ...
> > }  ?
> 
> Well, the plan is to eventually make duty_ns and period_ns unsigned int
> or unsigned long because negative values don't make any sense for them.
> With that in mind I think it makes sense to use the proper type here now.
> 

Okey, I will think it over again and revise it.

> > > > +static int fsl_pwm_config_channel(struct pwm_chip *chip,
> > >
> > > I think you can safely drop the _channel suffix from the PWM
> operations.
> > >
> >
> > By adding _channel suffix just for more comprehensave about the pwm's
> muti-channel operation.
> > If this is redundant here, I will drop it.
> 
> The operations are implicitly per-channel operations. So yes, the
> _channel suffix is redundant here.
> 

Agree, I will drop it.

> > > > +	fpc = to_fsl_chip(chip);
> > > > +
> > > > +	if (WARN_ON(!test_bit(PWMF_REQUESTED, &pwm->flags)))
> > > > +		return -ESHUTDOWN;
> > >
> > > Erm... how do you think this could ever happen? Users need to
> > > request a PWM to obtain a struct pwm_device, in which case
> > > PWMF_REQUESTED will always be set. There are a few other occurrences
> > > throughout the rest of the driver that I haven't pointed out
> explicitly.
> > >
> >
> > Does the following case is exist ?
> > The customer in one thread has .free(pwm_1), while in another thread,
> > which maybe had slept in for some reason, will
> call .config/.enable/.disable?
> >
> > If so, as I have explained before, if the pwm_1 has been freed, the
> > module clock maybe disabled too, so if the .config is call the system
> will hang up.
> 
> While the above could possibly happen, there's no way the core could
> prevent it. And your explicit test couldn't either. So what usually
> happens is that a driver requests a PWM device and then has exclusive
> access to it. Any other driver that wants to use the same PWM device
> can't because it will get an -EBUSY return.
> 
> So in your hypothetical case above, if one driver does stuff like that
> with a PWM device then that's a driver bug, not something the PWM core
> should be required to handle.
> 

Okey, I will drop this.

> > While I think the following is better in code.
> >
> >  		dev_err(fpc->chip.dev,
> >  			"failed to parse <fsl,pwm-clk-ps> property: %d\n",
> >  			ret);
> 
> Why? You're quoting which property failed to parse so you should use the
> correct character for quoting, which is either the apostrophe (') or the
> quotation mark (").
> 

For my first impression, I just thought that maybe a little better.
Okey, I will adopt this in the feature.



--
Xiubo

RE: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Xiubo Li-B47053]

Hi Stephen,


> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
> Freescale FTM PWM
> 
> On 08/23/2013 01:36 AM, Thierry Reding wrote:
> > On Thu, Aug 22, 2013 at 08:26:10AM +0200, Sascha Hauer wrote:
> >> On Thu, Aug 22, 2013 at 02:55:42AM +0000, Xiubo Li-B47053 wrote:
> >>> Hi Tomasz,
> >>>
> >>> Thanks for your comments.
> >>>
> >>>
> >>>> Could you explain meaning of this property more precisely?
> >>>> I'm interested especially how is this related to the PWM IP block
> >>>> and boards.
> >>>>
> >>>
> >>> Yes. There are 8 channels most. While the pinctrls of 4th and 5th
> >>> channels could be used by uart's Rx and Tx, then these 2 channels
> >>> won't be used for pwm output, so there will be 6 channels available
> >>> by the pwm. Thus, the pwm chip will register only 6 pwms(6 channels)
> >>> most("fsl,pwm-channel-orders = {0 1 2 3
> >>> 6 7}").And also the "fsl,pwm-channel-number" will be 6.
> >>
> >> If the chip has eight PWMs I would register all of them. If some of
> >> them are not routed out by the pinmux then just nothing happens if
> >> you use them. In a sane devicetree they won't be referenced anyway
> >> when they are not routed out of the SoC.
> >
> > In that case, shouldn't this be hooked up to the pinctrl subsystem as
> > well? As I understand the above, the logical thing would be for each
> > PWM channel's .request() operation to configure the pinmuxing
> > appropriately. And if it can't be configured as necessary then
> > .request() should return an error (or propagate the error from the
> > pinctrl subsystem).
> 
> I think the pin-muxing should be static, i.e. set up when the PWM device
> as a whole probe()s, rather than being twiddled at request/free time.
> Certainly the pinmux support in the device core is now set up to acquire
> the default state right before probe(). I don't see a need to do anything
> custom here.

As we have tolk about this before in [PATCH 1/4]:
"
> > Why do you need to manipulate the pinctrl to en/disable a channel?
> >
> 
> This is because in Vybrid VF610 TOWER board, there are 4 leds, and each
> led's one point(diode's positive pole) is connected to 3.3V, and the
> other point is connected to pwm's one channel. When the 4 pinctrls are
> configured as enable at the same time, the 4 pinctrls is low valtage, and
> the 4 leds will be lighted up as default, then when you enable/disable
> one led will effects others.
> 
> These pinctrls are belong to pwm, and I don't think led or other customer
> could control them directly.
> So, here I authorize the 4 pinctrls to each channel controls.
>
"
For the reason above, I have to control the pinctrls separately.

If all the pinctrls set as default state, the 8 pinctrls must be controlled together.
And the 4 leds will all be lighted up as default and will influence each other.

Thanks very much.

--
Best Regards.
Xiubo

Re: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Stephen Warren]

On 08/25/2013 11:35 PM, Xiubo Li-B47053 wrote:
>> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
...
>>> Why do you need to manipulate the pinctrl to en/disable a channel?
>>
>> This is because in Vybrid VF610 TOWER board, there are 4 leds, and each
>> led's one point(diode's positive pole) is connected to 3.3V, and the
>> other point is connected to pwm's one channel. When the 4 pinctrls are
>> configured as enable at the same time, the 4 pinctrls is low valtage, and
>> the 4 leds will be lighted up as default, then when you enable/disable
>> one led will effects others.
>>
>> These pinctrls are belong to pwm, and I don't think led or other customer
>> could control them directly.
>> So, here I authorize the 4 pinctrls to each channel controls.
>>
> "
> For the reason above, I have to control the pinctrls separately.
> 
> If all the pinctrls set as default state, the 8 pinctrls must be controlled together.
> And the 4 leds will all be lighted up as default and will influence each other.

Sorry, that still doesn't make much sense. Either way though, having
separate pinctrl setup for a single device isn't going to work. You'll
either need to have all combinations of 4 (8?) PWMs represented as
pinctrl states(!), or register separate PWM devices so that they get
independant pinctrl states.

RE: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Xiubo Li-B47053]

Hi Stephen,


> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
> Freescale FTM PWM
> 
> On 08/25/2013 11:35 PM, Xiubo Li-B47053 wrote:
> >> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
> ...
> >>> Why do you need to manipulate the pinctrl to en/disable a channel?
> >>
> >> This is because in Vybrid VF610 TOWER board, there are 4 leds, and
> >> each led's one point(diode's positive pole) is connected to 3.3V, and
> >> the other point is connected to pwm's one channel. When the 4
> >> pinctrls are configured as enable at the same time, the 4 pinctrls is
> >> low valtage, and the 4 leds will be lighted up as default, then when
> >> you enable/disable one led will effects others.
> >>
> >> These pinctrls are belong to pwm, and I don't think led or other
> >> customer could control them directly.
> >> So, here I authorize the 4 pinctrls to each channel controls.
> >>
> > "
> > For the reason above, I have to control the pinctrls separately.
> >
> > If all the pinctrls set as default state, the 8 pinctrls must be
> controlled together.
> > And the 4 leds will all be lighted up as default and will influence
> each other.
> 
> Sorry, that still doesn't make much sense. Either way though, having
> separate pinctrl setup for a single device isn't going to work. You'll
> either need to have all combinations of 4 (8?) PWMs represented as
> pinctrl states(!), or register separate PWM devices so that they get
> independant pinctrl states.
>
Well, I have ever thought about registering separate PWM device for each channel.
But, if so, how should I control the pinctrl of each PWM(actually one channel of FTM PWM) ?
I must select "default" state(the "default" state here, the pinctrl must be setup as "dsN" or "chN-idle" state we discussed before) when probing, and when customers .request-->.config-->.enable the PWM I also must select an "active" state to config the pinctrl...
Thus, this is still not static. I think this isn't much different from the current.

Also if having all combinations of 8 PWMs represented as pinctrl states, how could I deal with the problem about LEDs ?



Thanks very much,

--
Best Regards,
Xiubo

Re: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Stephen Warren]

On 08/26/2013 09:48 PM, Xiubo Li-B47053 wrote:
> Hi Stephen,
> 
> 
>> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
>> Freescale FTM PWM
>>
>> On 08/25/2013 11:35 PM, Xiubo Li-B47053 wrote:
>>>> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
>> ...
>>>>> Why do you need to manipulate the pinctrl to en/disable a channel?
>>>>
>>>> This is because in Vybrid VF610 TOWER board, there are 4 leds, and
>>>> each led's one point(diode's positive pole) is connected to 3.3V, and
>>>> the other point is connected to pwm's one channel. When the 4
>>>> pinctrls are configured as enable at the same time, the 4 pinctrls is
>>>> low valtage, and the 4 leds will be lighted up as default, then when
>>>> you enable/disable one led will effects others.
>>>>
>>>> These pinctrls are belong to pwm, and I don't think led or other
>>>> customer could control them directly.
>>>> So, here I authorize the 4 pinctrls to each channel controls.
>>>>
>>> "
>>> For the reason above, I have to control the pinctrls separately.
>>>
>>> If all the pinctrls set as default state, the 8 pinctrls must be
>> controlled together.
>>> And the 4 leds will all be lighted up as default and will influence
>> each other.
>>
>> Sorry, that still doesn't make much sense. ...

What may help here is to show the exact content you expect the various
en/dis states to have, so that we can see exactly which pinctrl options
get set when and why.

RE: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Xiubo Li-B47053]

Hi Thierry,


> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
> Freescale FTM PWM
> 
> On Thu, Aug 22, 2013 at 08:26:10AM +0200, Sascha Hauer wrote:
> > On Thu, Aug 22, 2013 at 02:55:42AM +0000, Xiubo Li-B47053 wrote:
> > > Hi Tomasz,
> > >
> > > Thanks for your comments.
> > >
> > >
> > > > Could you explain meaning of this property more precisely? I'm
> > > > interested especially how is this related to the PWM IP block and
> boards.
> > > >
> > >
> > > Yes.
> > > There are 8 channels most. While the pinctrls of 4th and 5th
> > > channels could be used by uart's Rx and Tx, then these 2 channels
> > > won't be used for pwm output, so there will be 6 channels available
> by the pwm.
> > > Thus, the pwm chip will register only 6 pwms(6 channels)
> > > most("fsl,pwm-channel-orders = {0 1 2 3 6 7}").And also the "fsl,pwm-
> channel-number" will be 6.
> >
> > If the chip has eight PWMs I would register all of them. If some of
> > them are not routed out by the pinmux then just nothing happens if you
> > use them. In a sane devicetree they won't be referenced anyway when
> > they are not routed out of the SoC.
> 
> In that case, shouldn't this be hooked up to the pinctrl subsystem as
> well? As I understand the above, the logical thing would be for each PWM
> channel's .request() operation to configure the pinmuxing appropriately.
> And if it can't be configured as necessary then .request() should return
> an error (or propagate the error from the pinctrl subsystem).
> 

That's maybe better, if so, the pinctrl configuration must be split into two steps:
1, get the channel pinctrl "active" and "idle" states by callig pinctrl_lookup_state() in .request().
2, select the proper state in .enable()/.disable().




Thanks very much.

--
Best Regards.
Xiubo

Re: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Kumar Gala]

Should have at least something w/regards to a commit message.

On Aug 20, 2013, at 10:07 PM, Xiubo Li wrote:

> Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
> ---
> .../devicetree/bindings/pwm/fsl-ftm-pwm.txt        | 52 ++++++++++++++++++++++
> 1 file changed, 52 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
> 
> diff --git a/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt b/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
> new file mode 100644
> index 0000000..698965b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
> @@ -0,0 +1,52 @@
> +Freescale FTM PWM controller
> +
> +Required properties:
> +- compatible: should be "fsl,vf610-ftm-pwm"
> +- reg: physical base address and length of the controller's registers
> +- #pwm-cells: Should be 3. Number of cells being used to specify PWM property.
> +  First cell specifies the per-chip channel index of the PWM to use, the
> +  second cell is the period in nanoseconds and bit 0 in the third cell is
> +  used to encode the polarity of PWM output. Set bit 0 of the third in PWM
> +  specifier to 1 for inverse polarity & set to 0 for normal polarity.
> +- fsl,pwm-clk-ps: the ftm0 pwm clock's prescaler, divide-by 2^n(n = 0 ~ 7).
> +- fsl,pwm-cpwm: Center-Aligned PWM (CPWM) mode.

Should describe this in more detail, what does the value actually mean for what modes there are?

> +- fsl,pwm-number: the number of PWM devices, and is must equal to the number
> +  of "fsl,pwm-channels".

If they must be equal why do we need both?

> +- fsl,pwm-channels: the channels' order which is be used for pwm in ftm0
> +  module, and they must be one or some of 0 ~ 7, because the ftm0 only has
> +  8 channels can be used.
> +- for very channel, the revlatived the pinctrl should be at least two state

revlatived?

> +  {"enN", "dsN"}, which "en" means "enable", "ds" means "disable" and "N"
> +  means the order of the channel.
> +
> +Example:
> +
> +pwm0: pwm@40038000 {
> +	      compatible = "fsl,vf610-ftm-pwm";
> +	      reg = <0x40038000 0x1000>;
> +	      #pwm-cells = <3>;
> +	      pinctrl-names = "en0", "ds0", "en3", "ds3";
> +	      pinctrl-0 = <&pinctrl_pwm0_ch0_en>;
> +	      pinctrl-1 = <&pinctrl_pwm0_ch0_ds>;
> +	      pinctrl-2 = <&pinctrl_pwm0_ch3_en>;
> +	      pinctrl-3 = <&pinctrl_pwm0_ch3_ds>;
> +	      fsl,pwm-clk-ps = <7>;
> +	      fsl,pwm-cpwm = <0>;
> +	      fsl,pwm-number = <2>;
> +	      fsl,pwm-channels = <0 3>;
> +	      ...
> +      };
> +
> +leds {
> +	compatible = "pwm-leds";
> +	led {
> +		label = "fsl_led";
> +		pwms = <&pwm0 0 10000000 0>;
> +		max-brightness = <127>;
> +	};
> +	backlight {
> +		label = "fsl_backlight";
> +		pwms = <&pwm0 3 10000000 1>;
> +		max-brightness = <100>;
> +	};
> +};
> -- 
> 1.8.0
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Stephen Warren]

On 08/30/2013 01:19 PM, Kumar Gala wrote:
> Should have at least something w/regards to a commit message.
> 
> On Aug 20, 2013, at 10:07 PM, Xiubo Li wrote:
> 
>> Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
>> ---
>> .../devicetree/bindings/pwm/fsl-ftm-pwm.txt        | 52 ++++++++++++++++++++++
>> 1 file changed, 52 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
>>
>> diff --git a/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt b/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
>> new file mode 100644
>> index 0000000..698965b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
>> @@ -0,0 +1,52 @@
>> +Freescale FTM PWM controller
>> +
>> +Required properties:
>> +- compatible: should be "fsl,vf610-ftm-pwm"
>> +- reg: physical base address and length of the controller's registers
>> +- #pwm-cells: Should be 3. Number of cells being used to specify PWM property.
>> +  First cell specifies the per-chip channel index of the PWM to use, the
>> +  second cell is the period in nanoseconds and bit 0 in the third cell is
>> +  used to encode the polarity of PWM output. Set bit 0 of the third in PWM
>> +  specifier to 1 for inverse polarity & set to 0 for normal polarity.
>> +- fsl,pwm-clk-ps: the ftm0 pwm clock's prescaler, divide-by 2^n(n = 0 ~ 7).
>> +- fsl,pwm-cpwm: Center-Aligned PWM (CPWM) mode.
> 
> Should describe this in more detail, what does the value actually mean for what modes there are?

Assuming "CPWM" is clearly explained in the HW documentation for this
chip (I have no idea if that's actually the case), then is it still
necessary to explain what this means in *detail*? Perhaps simply "see
section XXX in the TRM" or "see register XXX, bit YYY in the HW
documentation" would be enough?

RE: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Xiubo Li-B47053]

> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
> Freescale FTM PWM
> 
> On 08/30/2013 01:19 PM, Kumar Gala wrote:
> > Should have at least something w/regards to a commit message.
> >
> > On Aug 20, 2013, at 10:07 PM, Xiubo Li wrote:
> >
> >> Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
> >> ---
> >> .../devicetree/bindings/pwm/fsl-ftm-pwm.txt        | 52
> ++++++++++++++++++++++
> >> 1 file changed, 52 insertions(+)
> >> create mode 100644
> >> Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
> >> b/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
> >> new file mode 100644
> >> index 0000000..698965b
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/pwm/fsl-ftm-pwm.txt
> >> @@ -0,0 +1,52 @@
> >> +Freescale FTM PWM controller
> >> +
> >> +Required properties:
> >> +- compatible: should be "fsl,vf610-ftm-pwm"
> >> +- reg: physical base address and length of the controller's
> >> +registers
> >> +- #pwm-cells: Should be 3. Number of cells being used to specify PWM
> property.
> >> +  First cell specifies the per-chip channel index of the PWM to use,
> >> +the
> >> +  second cell is the period in nanoseconds and bit 0 in the third
> >> +cell is
> >> +  used to encode the polarity of PWM output. Set bit 0 of the third
> >> +in PWM
> >> +  specifier to 1 for inverse polarity & set to 0 for normal polarity.
> >> +- fsl,pwm-clk-ps: the ftm0 pwm clock's prescaler, divide-by 2^n(n = 0
> ~ 7).
> >> +- fsl,pwm-cpwm: Center-Aligned PWM (CPWM) mode.
> >
> > Should describe this in more detail, what does the value actually mean
> for what modes there are?
> 
> Assuming "CPWM" is clearly explained in the HW documentation for this
> chip (I have no idea if that's actually the case), then is it still
> necessary to explain what this means in *detail*? Perhaps simply "see
> section XXX in the TRM" or "see register XXX, bit YYY in the HW
> documentation" would be enough?
>
If to clearly explain the 'CPWM' mode, there maybe need much more words, I think just simply explain it, and then for more detail information "see section XXX in the TRM" or "see register XXX, bit YYY in HW documentation".


Thanks.

--
Best Regards,
Xiubo

RE: [PATCH 4/4] Documentation: Add device tree bindings for Freescale FTM PWM

[Xiubo Li-B47053]

> Subject: Re: [PATCH 4/4] Documentation: Add device tree bindings for
> Freescale FTM PWM
> 
> Should have at least something w/regards to a commit message.
> 

I have sent a V2 patch and have added it.


> > +  used to encode the polarity of PWM output. Set bit 0 of the third
> > +in PWM
> > +  specifier to 1 for inverse polarity & set to 0 for normal polarity.
> > +- fsl,pwm-clk-ps: the ftm0 pwm clock's prescaler, divide-by 2^n(n = 0
> ~ 7).
> > +- fsl,pwm-cpwm: Center-Aligned PWM (CPWM) mode.
> 
> Should describe this in more detail, what does the value actually mean
> for what modes there are?
> 

It's maybe a very useful feature for FTM core, but for PWM is not.
This isn't needed any more for PWM, and in V2 patch I have removed CPWM mode.

> > +- fsl,pwm-number: the number of PWM devices, and is must equal to the
> > +number
> > +  of "fsl,pwm-channels".
> 
> If they must be equal why do we need both?
> 

I have replaced both of them too in V2.

> > +- fsl,pwm-channels: the channels' order which is be used for pwm in
> > +ftm0
> > +  module, and they must be one or some of 0 ~ 7, because the ftm0
> > +only has
> > +  8 channels can be used.
> > +- for very channel, the revlatived the pinctrl should be at least two
> > +state
> 
> revlatived?
> 

This too.

--
Best Regards.
Xiubo