linux-kernel - Re: [rfc]pwm: add BCM2835 PWM driver

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Date:	Tue, 08 Apr 2014 19:27:37 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Tim Kryger <tim.kryger@...aro.org>,
	Bart Tanghe <bart.tanghe@...masmore.be>
CC:	Thierry Reding <thierry.reding@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux PWM List <linux-pwm@...r.kernel.org>,
	linux-rpi-kernel@...ts.infradead.org
Subject: Re: [rfc]pwm: add BCM2835 PWM driver

On 04/08/2014 05:02 PM, Tim Kryger wrote:
> On Thu, Apr 3, 2014 at 6:44 AM, Bart Tanghe <bart.tanghe@...masmore.be> wrote:
>> need some recommendation
>> the memory mapped io registers of the bcm2835 pwm hardware are spreaded
>> over the memory mapped io
>> gpio config 0x20200004 - clk config 0x201010A0 - pwm configuration 0x2020C000
>> to handle this, I've used the base address of the memory mapped io
>> so I can use positive offsets
> 
> So the registers for this PWM are located in three distinct memory regions?
...
>> +struct bcm2835_pwm_chip {
>> +       struct pwm_chip chip;
>> +       struct device *dev;
>> +       int channel;
>> +       void __iomem *mmio;
> 
> One pointer isn't going to be enough.  You need three.
> 
> I suggest renaming the first and adding two more:
> 
> void __iomem *base_pwm;
> void __iomem *base_clk;
> void __iomem *base_alt;

Sorry, I forgot about this patch. One comment here; the PWM driver can't
touch the clock or alt registers; those should be owned by the clock
driver, and the driver for whatever alt is (pinmux - don't recall what
it's touching there).
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