Date: Sat, 18 Aug 2012 11:52:12 +0200
From: Wolfram Sang <w.sang@pengutronix.de>
To: Roland Stigge <stigge@antcom.de>
Cc: vitalywool@gmail.com, khali@linux-fr.org, ben-linux@fluff.org,
        grant.likely@secretlab.ca, linux-i2c@vger.kernel.org,
        linux-kernel@vger.kernel.org, kevin.wells@nxp.com,
        srinivas.bakki@nxp.com, aletes.xgr@gmail.com, jonsmirl@gmail.com
Subject: Re: [PATCH RESEND 2/2] i2c: pnx: Fix read transactions of >= 2 bytes
Message-ID: <20120818095212.GC24812@pengutronix.de>
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On Wed, Aug 08, 2012 at 09:42:32AM +0200, Roland Stigge wrote:
> On transactions with n>=3D2 bytes, the controller actually wrongly clocks=
 in n+1
> bytes. This is caused by the (wrong) assumption that RFE in the Status Re=
gister
> is 1 iff there is no byte already ordered (via a dummy TX byte). This lea=
d to
> the implementation of synchronized byte ordering, e.g.:
>=20
> Dummy-TX - RX - Dummy-TX - RX - ...
>=20
> But since RFE actually stays high after some Dummy-TX, it rather looks li=
ke:
>=20
> Dummy-TX - Dummy-TX - RX - Dummy-TX - RX - (RX)
>=20
> The last RX byte is clocked in by the bus controller, but ignored by the =
kernel
> when filling the userspace buffer.
>=20
> This patch fixes the issue by asking for RX via Dummy-TX asynchronously.
> Introducing a separate counter for TX bytes.
>=20
> Signed-off-by: Roland Stigge <stigge@antcom.de>
>=20
> ---
> Applies to v3.6-rc1
>=20
> This patch for i2c-pnx affects PNX4008 and LPC32xx (and LPC31xx, not yet =
in
> mainline). Can you please test?
>=20
> Thanks in advance!

I assume you checked this on LPC32xx? I'll wait a bit more but tend to
take the patch anyhow, even if there is no explicit ACK from PNX.

--=20
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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