From: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
To: Oliver Schinagl <oliver+list-dxLnbx3+1qmEVqv0pETR8A@public.gmane.org>
Cc: linux-sunxi-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org,
Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
Emilio Lopez <emilio-0Z03zUJReD5OxF6Tv1QG9Q@public.gmane.org>,
kevin-0TFLnhJekD6UEPyfVivIlAC/G2K4zDHf@public.gmane.org,
sunny-0TFLnhJekD6UEPyfVivIlAC/G2K4zDHf@public.gmane.org,
shuge-0TFLnhJekD6UEPyfVivIlAC/G2K4zDHf@public.gmane.org,
linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCHv2 1/6] i2c: sunxi: Add Allwinner A1X i2c driver
Date: Mon, 27 May 2013 12:04:53 +0200 [thread overview]
Message-ID: <20130527100453.GM17847@lukather> (raw)
In-Reply-To: <51A25C21.2060700-dxLnbx3+1qmEVqv0pETR8A@public.gmane.org>
Hi Oliver,
On Sun, May 26, 2013 at 09:01:53PM +0200, Oliver Schinagl wrote:
> On 05/26/13 15:21, Maxime Ripard wrote:
> >For the iowrite* vs write*, there's no consensus, and as such no
> >preferred way. write* functions are doing an MMIO only access,
> >while iowrite functions can do MMIO and port I/O accesses.
> >
> >Note that it doesn't change anything on ARM, since there's no port IO on
> >ARM.
> Ah I see, missinformation on my end. Sorry.
>
> But why write 32 bits? The register is only 8 wide, with the rest
> being 'reserved'. Then again, the register IS 32 bits wide and
> probably will haev 32 bits written to it? Correct?
Yes, the register is 32 bits wide. However, and I didn't noticed it at
first, that all the registers have the 3 upper bytes reserved.
But you'll end up writing a 32 bits value to a 32 bit register register
anyway, even if the relevant information is contained in the 8 first
bits.
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
next prev parent reply other threads:[~2013-05-27 10:04 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-26 10:20 [PATCHv2 0/6] Add I2C support for Allwinner SoCs Maxime Ripard
[not found] ` <1369563642-4390-1-git-send-email-maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
2013-05-26 10:20 ` [PATCHv2 1/6] i2c: sunxi: Add Allwinner A1X i2c driver Maxime Ripard
[not found] ` <1369563642-4390-2-git-send-email-maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
2013-05-26 10:53 ` Oliver Schinagl
[not found] ` <51A1E9AA.4000008-dxLnbx3+1qmEVqv0pETR8A@public.gmane.org>
2013-05-26 13:21 ` [linux-sunxi] " Maxime Ripard
2013-05-26 19:01 ` Oliver Schinagl
[not found] ` <51A25C21.2060700-dxLnbx3+1qmEVqv0pETR8A@public.gmane.org>
2013-05-27 10:04 ` Maxime Ripard [this message]
2013-05-26 14:44 ` [linux-sunxi] " Tomasz Figa
2013-05-26 19:05 ` Oliver Schinagl
2013-05-26 14:38 ` Tomasz Figa
2013-05-26 17:00 ` Maxime Ripard
2013-05-26 10:20 ` [PATCHv2 2/6] ARM: sunxi: dt: Add i2c controller nodes to the DTSI Maxime Ripard
2013-05-26 10:20 ` [PATCHv2 3/6] ARM: sun4i: dt: Add i2c muxing options Maxime Ripard
2013-05-26 10:20 ` [PATCHv2 4/6] ARM: sun5i: " Maxime Ripard
2013-05-26 10:20 ` [PATCHv2 5/6] ARM: sun5i: olinuxino: Enable the i2c controllers Maxime Ripard
2013-05-26 10:20 ` [PATCHv2 6/6] ARM: sun4i: cubieboard: " Maxime Ripard
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