linux-kernel - Re: [PATCH 2/2] pwm: samsung: fix the number of PWMs

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Date:	Fri, 03 Aug 2012 08:17:59 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Thierry Reding' <thierry.reding@...onic-design.de>
Cc:	linux-kernel@...r.kernel.org, 'Jingoo Han' <jg1.han@...sung.com>
Subject: Re: [PATCH 2/2] pwm: samsung: fix the number of PWMs

On Thursday, August 02, 2012 6:54 PM Thierry Reding wrote:
> 
> On Thu, Aug 02, 2012 at 05:56:27PM +0900, Jingoo Han wrote:
> > Samsung SoC can provide 4 PWMs; thus, the number of PWMs should be
> > set as 4.
> >
> > Signed-off-by: Jingoo Han <jg1.han@...sung.com>
> > ---
> >  drivers/pwm/pwm-samsung.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c
> > index e5187c0..32562c6 100644
> > --- a/drivers/pwm/pwm-samsung.c
> > +++ b/drivers/pwm/pwm-samsung.c
> > @@ -228,7 +228,7 @@ static int s3c_pwm_probe(struct platform_device *pdev)
> >  	s3c->chip.dev = &pdev->dev;
> >  	s3c->chip.ops = &s3c_pwm_ops;
> >  	s3c->chip.base = -1;
> > -	s3c->chip.npwm = 1;
> > +	s3c->chip.npwm = 4;
> 
> I don't think this is correct. The driver seems to be using the platform
> device id as index currently, which indicates that the driver is bound
> against 4 different platform devices, each representing a single PWM. If
> you want to service multiple PWM devices by a single instance you need
> to make further changes to the driver. For instance the tcon_base is
> initialized based on the platform id. This could easily be replaced by
> making it depend on the .hwpwm member of pwm_device.

I just want to use pwm backlight on Samsung SoC boards.
After moving samusng pwm driver from 'arch/arm/plat-samsung/'
to 'drivers/pwm/', pwm bakclight does not work properly.

When pwm_id is '1' and PWM backlight calls pwm_request(data->pwm_id,
"pwm-backlight"), pwm_to_device() returns NULL.

Then, do you mean that?
	s3c->chip.npwm = id + 1;

> 
> You may also want to consider making the driver a proper module if that
> works on the platforms that need it. I see that it is currently an
> arch_initcall, but it might be cleaner to use deferred driver probe
> instead.

Sorry, I cannot understand what you say.

> 
> Thierry

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