linux-kernel - Re: [PATCH v9 01/25] gpio/omap: remove dependency on gpio_bank

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Date:	Thu, 2 Feb 2012 23:53:51 +0200
From:	Felipe Balbi <balbi@...com>
To:	Felipe Balbi <balbi@...com>
Cc:	"Cousson, Benoit" <b-cousson@...com>, khilman@...com,
	Grant Likely <grant.likely@...retlab.ca>,
	Tarun Kanti DebBarma <tarun.kanti@...com>,
	linux-omap@...r.kernel.org, tony@...mide.com,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Charulatha V <charu@...com>
Subject: Re: [PATCH v9 01/25] gpio/omap: remove dependency on gpio_bank_count

Hi again,

On Thu, Feb 02, 2012 at 11:49:08PM +0200, Felipe Balbi wrote:
> > In fact the driver already handled the 6 GPIOS banks as individual devices:
> > 
> > [    0.185638] gpiochip_add: registered GPIOs 0 to 31 on device: gpio
> > [    0.185882] OMAP GPIO hardware version 0.1
> > [    0.186767] gpiochip_add: registered GPIOs 32 to 63 on device: gpio
> > [    0.187744] gpiochip_add: registered GPIOs 64 to 95 on device: gpio
> > [    0.188751] gpiochip_add: registered GPIOs 96 to 127 on device: gpio
> > [    0.189819] gpiochip_add: registered GPIOs 128 to 159 on device: gpio
> > [    0.190917] gpiochip_add: registered GPIOs 160 to 191 on device: gpio
> 
> yeah, but you can get all of that for free from driver core. Just add
> one platform_device for each bank and make the omap-gpio.c only
> understand one bank. No tricks.
> 
> What I'm trying to say is to remove the Bank array or list_head and make
> probe() get called 6 times by creating 6 omap_gpio platform_devices.
> 
> From probe you cann gpiochip_add() once and only once.
		 ^^^^
		 call

I actually just took the time to go over the driver and that's what it
does. So the list_head is only there fo the nasty cpuidle stuff below:

> > That list is only used to iterate over all the instances during CPU idle:
> > 
> > void omap2_gpio_prepare_for_idle(int pwr_mode)
> > {
> > 	struct gpio_bank *bank;
> > 
> > 	list_for_each_entry(bank, &omap_gpio_list, node) {
> > 		if (!bank->mod_usage || !bank->loses_context)
> > 			continue;
> > 
> > 		bank->power_mode = pwr_mode;
> > 
> > 		pm_runtime_put_sync_suspend(bank->dev);
> > 	}
> > }
> > 
> > void omap2_gpio_resume_after_idle(void)
> > {
> > 	struct gpio_bank *bank;
> > 
> > 	list_for_each_entry(bank, &omap_gpio_list, node) {
> > 		if (!bank->mod_usage || !bank->loses_context)
> > 			continue;
> > 
> > 		pm_runtime_get_sync(bank->dev);
> > 	}
> > }
> 
> that's the thing which is unnecessary, actually :-)
> 
> Why do we even have this omap2_gpio_resume_after_idle() ? Can't the gpio
> driver handle its own PM or listen to cpuidle notificaitons for that ?
> 
> I would like to understand why do we need this hack for pm runtime.
> Can't you just use ->prepare() and ->complete() from dev_pm_ops ?

This question remains. Why do we need those funtions ?

-- 
balbi

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