linux-kernel - Re: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

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Message-ID: <20121215105157.GN14363@n2100.arm.linux.org.uk>
Date:	Sat, 15 Dec 2012 10:51:57 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Roland Stigge <stigge@...com.de>
Cc:	Wolfgang Grandegger <wg@...ndegger.com>, rmallon@...il.com,
	gregkh@...uxfoundation.org, linus.walleij@...aro.org,
	broonie@...nsource.wolfsonmicro.com, linux-kernel@...r.kernel.org,
	w.sang@...gutronix.de, grant.likely@...retlab.ca,
	daniel-gl@....net, sr@...x.de, plagnioj@...osoft.com,
	linux-arm-kernel@...ts.infradead.org, highguy@...il.com
Subject: Re: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

On Sat, Dec 15, 2012 at 12:49:57AM +0100, Roland Stigge wrote:
> Without having an AT91 available right now, I guess the hardware
> interface of this GPIO chip is different from the GPIO block API. While
> the hardware has clear and set registers, the val parameter of
> at91_gpiolib_set_block() should be interpreted as the actual output
> values. See lpc32xx_gpo_set_block() for an example for handling set and
> clear registers like this: First, set_bits and clear_bits words are
> calculated from mask and val parameters, and finally written to the
> respective hardware registers.
> 
> Note that one .set_block() can result in writing both the set and clear
> registers of the hardware when val contains both 0s and 1s in
> respectively masked positions.

Note also that if this is the same IP as found in SAM3N devices, that it's
possible to write the bit values directly through the OWER/OWDR (output
write enable register/disable register) plus the ODSR (output data status
register) which will synchronously change the state of all the
write-enabled output pins.  That may be important for some applications.
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