linux-kernel - RE: [PATCH 08/09] ARM: s3c2440: gta02: Request usb pullup pin before using it

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Message-id: <003201cbd734$79d87050$6d8950f0$%kim@samsung.com>
Date:	Mon, 28 Feb 2011 19:44:25 +0900
From:	Kukjin Kim <kgene.kim@...sung.com>
To:	'Lars-Peter Clausen' <lars@...afoo.de>
Cc:	'Ben Dooks' <ben-linux@...ff.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: RE: [PATCH 08/09] ARM: s3c2440: gta02: Request usb pullup pin before
 using it

Lars-Peter Clausen wrote:
> 
> On 02/28/2011 07:16 AM, Kukjin Kim wrote:
> > Lars-Peter Clausen wrote:
> >>
> >> Request the gpio pin used to control the usb pullup before using it to
> > avoid
> >> a
> >> runtime warning about an auto-requested gpio.
> >>
> >> Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
> >> ---
> >>  arch/arm/mach-s3c2440/mach-gta02.c |   17 +++++++++++++++--
> >>  1 files changed, 15 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/arm/mach-s3c2440/mach-gta02.c
> > b/arch/arm/mach-s3c2440/mach-
> >> gta02.c
> >> index 1396639..94456fa 100644
> >> --- a/arch/arm/mach-s3c2440/mach-gta02.c
> >> +++ b/arch/arm/mach-s3c2440/mach-gta02.c
> >> @@ -451,11 +451,11 @@ static void gta02_udc_command(enum
s3c2410_udc_cmd_e
> >> cmd)
> >>  	switch (cmd) {
> >>  	case S3C2410_UDC_P_ENABLE:
> >>  		pr_debug("%s S3C2410_UDC_P_ENABLE\n", __func__);
> >> -		gpio_direction_output(GTA02_GPIO_USB_PULLUP, 1);
> >> +		gpio_set_value(GTA02_GPIO_USB_PULLUP, 1);
> >
> > How about following instead?
> > 	gpio_request(GTA02_GPIO_USB_PULLUP, "USB_PULLUP");
> > 	gpio_direction_output(GTA02_GPIO_USB_PULLUP, 1);
> > 	gpio_free(GTA02_GPIO_USB_PULLUP);
> >
> 
> I don't think that is a good idea. This gpio should really be reserved for
> the
> udc driver. If it is freed again, it could be requested from someone else
> which
> could lead to undefined behaviour.
> 
Yes right, but I mean the board designer already knows the usage of
regarding GPIOs on his board.
So why do we really need gpio_request for it?...

Thanks.

Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@...sung.com>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.

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