From mboxrd@z Thu Jan 1 00:00:00 1970 From: thierry.reding@gmail.com (Thierry Reding) Date: Wed, 11 Dec 2013 16:21:20 +0100 Subject: [PATCH v8 1/2] PWM: atmel-pwm: add PWM controller driver In-Reply-To: <52A67A71.6020404@atmel.com> References: <1384766002-2852-1-git-send-email-voice.shen@atmel.com> <20131202105957.GD18060@ulmo.nvidia.com> <529D4B58.9020700@atmel.com> <52A67A71.6020404@atmel.com> Message-ID: <20131211152119.GD31617@ulmo.nvidia.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 836 bytes Desc: not available URL: