On Tue, Dec 10, 2013 at 10:20:33AM +0800, Bo Shen wrote: > Hi Thierry, > > On 12/03/2013 11:09 AM, Bo Shen wrote: > >>>+ atmel_pwm->chip.of_xlate = of_pwm_xlate_with_flags; > >>>+ atmel_pwm->chip.of_pwm_n_cells = 3; > >>>+ atmel_pwm->chip.base = -1; > >>>+ } else { > >>>+ atmel_pwm->chip.base = pdev->id; > >> > >>That's not correct. The chip cannot be tied to pdev->id, because that ID > >>is the instance number of the device. So typically you would have > >>devices name like this: > >> > >> atmel-pwm.0 > >> atmel-pwm.1 > >> ... > >> > >>Now, if you have that, then you won't be able to register the second > >>instance because the first instance will already have requested PWMs > >>0-3, and setting .base to 1 will cause PWMs 1-4 to be requested, which > >>intersects with the range of the first instance. > >> > >>The same applies of course if you have other PWM controllers in the > >>system which have similar instance names. > >> > >>So the right thing to do here is to provide that number via platform > >>data so that platform code can define it, knowing in advance all ranges > >>for all other PWM controllers and thereby make sure there's no > >>intersection. > > > >OK, I will fix this. > > After read deeply of PWM framework, for non device tree, I think we'd better > let the PWM core to choose chip.base as device tree, while not pass a number > through platform data to it. Or else, it will confuse the user to set the > chip.base, must set it in correct value to avoid intersection. And, actually > we won't use chip.base in driver itself. Yes, that should work as well, if you make sure that every user actually has the PWM lookup table and doesn't rely on a fixed global index to retrieve the PWM channel. Thierry
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