From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH 1/8 v2] i2c: i2c-bfin-twi: Illegal i2c bus lock upon certain transfer scenarios. Date: Fri, 13 Jul 2012 08:31:11 +0200 Message-ID: <20120713063111.GA32184@pengutronix.de> References: <1339575767-22985-1-git-send-email-sonic.adi@gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="17pEHd4RhPHOinZp" Return-path: Content-Disposition: inline In-Reply-To: <1339575767-22985-1-git-send-email-sonic.adi@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Sonic Zhang Cc: Ben Dooks , linux-i2c@vger.kernel.org, LKML , uclinux-dist-devel@blackfin.uclinux.org, Michael Hennerich , Sonic Zhang List-Id: linux-i2c@vger.kernel.org --17pEHd4RhPHOinZp Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 13, 2012 at 04:22:40PM +0800, Sonic Zhang wrote: > From: Michael Hennerich >=20 > For transfer counts > 255 bytes i2c-bfin-twi sets the data > transfer counter DCNT to 0xFF indicating unlimited transfers. > It then uses a flag iface->manual_stop to manually issue the STOP > condition, once the required amount of bytes are received. >=20 > We found that on I2C receive operation issuing the STOP condition > together with a FULL RCV FIFO (2bytes) will cause SDA and SCL be > constantly driven low. >=20 > Temporary workaround until further investigation: > Discard the RCV FIFO before issuing the STOP condition. >=20 > Signed-off-by: Michael Hennerich > Signed-off-by: Sonic Zhang All 8 patches applied to next, thanks. If you want to make my life easier, please state what changed from V1 to V2. I had to look it up manually which costs time and doesn't make the patchset look like a low-hanging fruit. > --- > drivers/i2c/busses/i2c-bfin-twi.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) >=20 > diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-b= fin-twi.c > index cdb59e5..33031f0 100644 > --- a/drivers/i2c/busses/i2c-bfin-twi.c > +++ b/drivers/i2c/busses/i2c-bfin-twi.c > @@ -131,6 +131,10 @@ static void bfin_twi_handle_interrupt(struct bfin_tw= i_iface *iface, > iface->transPtr++; > iface->readNum--; > } else if (iface->manual_stop) { > + /* Temporary workaround to avoid possible bus stall - > + * Flush FIFO before issuing the STOP condition > + */ > + read_RCV_DATA16(iface); > write_MASTER_CTL(iface, > read_MASTER_CTL(iface) | STOP); > } else if (iface->cur_mode =3D=3D TWI_I2C_MODE_REPEAT && > --=20 > 1.7.0.4 >=20 >=20 --=20 Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ | --17pEHd4RhPHOinZp Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAk//wK8ACgkQD27XaX1/VRs9vwCfckUN7xf8NhWLVFAKEfAeHu+7 eXAAnj+EK2TXSCGjR8oJyXKEmv+IyE6l =sMck -----END PGP SIGNATURE----- --17pEHd4RhPHOinZp--