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

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Date:	Sun, 5 Feb 2012 14:46:19 +0530
From:	"Shilimkar, Santosh" <santosh.shilimkar@...com>
To:	balbi@...com
Cc:	"Varadarajan, Charulatha" <charu@...com>,
	Kevin Hilman <khilman@...com>,
	"Cousson, Benoit" <b-cousson@...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
Subject: Re: [PATCH v9 01/25] gpio/omap: remove dependency on gpio_bank_count

On Sun, Feb 5, 2012 at 2:38 PM, Felipe Balbi <balbi@...com> wrote:
> Hi,
>
> On Sun, Feb 05, 2012 at 12:37:55PM +0530, Varadarajan, Charulatha wrote:
>> Felipe,
>>
>> On Sat, Feb 4, 2012 at 21:38, Felipe Balbi <balbi@...com> wrote:

[....]

>> bank->mod_usage check is used to take care of doing pm_runtime_get*/put* only
>> if all the GPIOs in a particular bank are enabled or disabled respectively.
>
> and why should you care about that ? The first get will enable the
> resources you need, the second get will just increase a counter and so
> on. So if you have 32 gets, you will disable the module when you have 32
> puts.
>
Am not sure if it is clear to you that the GPIO resources like clock,
debounce clk are per bank wise and not per GPIO line. So doing 32
get/put per bank is stupid. runtime pm is for managing pm
resources and if the pm resource is per bank, it has to be
handled per bank.

>> With the above change, pm_runtime_put*/get* would be called for every
>> gpio_request()
>> /_free() (that is, for upto 32 pins in OMAP3/4) in a bank irrespective
>> of whether other
>
> so ?
It's useless.

>
>> GPIO pins are enabled or disabled in the same bank. Hence it is
>> required to have a
>> check based on mod_usage.
>
> unnecessary.
>
I don't think so.

Regards
Santosh
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