linux-kernel - Re: [PATCH v2 7/7] ARM: davinci: Start using gpiolib API inplace of inline functions

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Message-ID: <51C2C909.7060001@ti.com>
Date:	Thu, 20 Jun 2013 14:49:05 +0530
From:	Sekhar Nori <nsekhar@...com>
To:	Philip Avinash <avinashphilip@...com>
CC:	<khilman@...prootsystems.com>, <linux@....linux.org.uk>,
	<grant.likely@...retlab.ca>, <linus.walleij@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<davinci-linux-open-source@...ux.davincidsp.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/7] ARM: davinci: Start using gpiolib API inplace
 of inline functions

On 6/14/2013 3:05 PM, Philip Avinash wrote:
> Remove NEED_MACH_GPIO_H config select option for ARCH_DAVINCI to start
> use gpiolib interface for davinci platforms. However with this software
> latencies for gpio_get/set APIs will affect. Latency has increased by 18
> microsecond with gpiolib API as compared with inline API's.
> 
> Software latency is calculated on da850 EVM for gpio_get_value API by
> taking the printk timing for API execution with interrupts disabled.
> Experiment has done for inline and gpiolib API interface.
> 
>   inline gpio API with interrupt disabled
>   [   29.734337] before gpio_get
>   [   29.736847] after gpio_get
> 
>   Time difference 0.00251
> 
>   gpio library with interrupt disabled
>   [  272.876763] before gpio_get
>   [  272.879291] after gpio_get
> 
>   Time difference 0.002528
>   Latency increased by (0.002528 -  0.00251) = 18 microsecond.
> 
> Also being here
> - Moved following definitions from mach folder to include directory
> 	struct davinci_gpio_controller
> 	Macro GPIO(x)
> 	inline function __gpio_mask

> - Removed GPIO_TYPE_DAVINCI enum definition as GPIO Davinci is converted
>   to Linux device driver model.

This is bit out-of-place here. Why not do it along with removal of its
last usage in <soc>.c files?

Rest of the patch looks good to me.

Thanks,
Sekhar
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