Re: [PATCH] drivers/pwm: add PXA pulse width modulator controller

From: Robert Jarzmik <robert.jarzmik@free.fr>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH] drivers/pwm: add PXA pulse width modulator controller
Date: Fri, 03 Feb 2012 16:39:18 +0100	[thread overview]
Message-ID: <87mx903p09.fsf@free.fr> (raw)
In-Reply-To: <20120203095205.GF1990@pengutronix.de> (Sascha Hauer's message of "Fri, 3 Feb 2012 10:52:05 +0100")

Sascha Hauer <s.hauer@pengutronix.de> writes:

> Hi Robert,
>
> Why not implement it as a regular driver? If we ever want to implement
> a commandline control of the pwms via pwm0.dutyns=xx we'll need
> a struct device.

This is because in my own case, I need pwm to be registered before other devices
are probed. The trouble (in my case) is that for drivers/video/pxa.c, I have the
following call path :
 - pxafb_probe()
   -> pxafb_enable_controller()
     -> pxafb_backlight_power()
       -> mioa701_lcd_backlight()
          => 	struct pwm_device *pwm0 = pwm_request("pxa_pwm0");
		pwm_enable(pwm0);
		pwm_config(pwm0, 2000 * 1024, 4000 * 1024);

I'm a bit afraid that the pxafb driver will be probed first, before pwm_pxa, and
therefore the backlight setting won't work. I haven't found a clean way to
specify this dependency.

Cheers.

-- 
Robert

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