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

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Date:	Wed, 19 Jun 2013 21:05:12 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Philip Avinash <avinashphilip@...com>
Cc:	"Nori, Sekhar" <nsekhar@...com>,
	ext Kevin Hilman <khilman@...prootsystems.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...retlab.ca>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"davinci-linux-open-source@...ux.davincidsp.com" 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/7] ARM: davinci: Start using gpiolib API inplace of
 inline functions

On Fri, Jun 14, 2013 at 11:35 AM, Philip Avinash <avinashphilip@...com> 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.
> - With removal of select option of NEED_MACH_GPIO_H for ARCH_DAVINCI,
>   gpio-tnetv107x also start using gpiolib interface. Hence removes
>   related header files
>         arch/arm/mach-davinci/include/mach/gpio-davinci.h
>         arch/arm/mach-davinci/include/mach/gpio.h
>
>   and include linux/platform_data/gpio-davinci.h header file to support
>   gpio-davinci platform definitions.
>
> Signed-off-by: Philip Avinash <avinashphilip@...com>
> Signed-off-by: Sekhar Nori <nsekhar@...com>
> ---
> Changes since v1:
>         - Remove inline GPIO API support for tnetv107x platforms
>         - Remove gpio header files in mach directory.
>         - Remove include of gpio header files from mach directory.
>         - Moved enum davinci_gpio_type to include folder
>         - Replace __ASM_ARCH_DAVINCI_GPIO_H with __DAVINCI_GPIO_PLATFORM_H

Acked-by: Linus Walleij <linus.walleij@...aro.org>
on this as well, and this whole 7-patch series.

For sure things look better after this series than before it,
even if there may be details I think need to be adressed later.

Yours,
Linus Walleij
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