From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH 1/3] mpc52xx_spi: fix clearing status register Date: Wed, 11 Nov 2009 10:48:38 +0100 Message-ID: <20091111094838.GA4234@pengutronix.de> References: <1257844329-20687-1-git-send-email-l.fu@pengutronix.de> <1257844329-20687-2-git-send-email-l.fu@pengutronix.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="pf9I7BMVVzbSWLtt" Cc: Grant Likely , spi-devel-general@lists.sourceforge.net, David Brownell , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org To: Luotao Fu Return-path: Content-Disposition: inline In-Reply-To: <1257844329-20687-2-git-send-email-l.fu@pengutronix.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org --pf9I7BMVVzbSWLtt Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Nov 10, 2009 at 10:12:07AM +0100, Luotao Fu wrote: > Before reading status register to check MODF failure, we have to clear it > first since the MODF flag will be set after initializing the spi master, > if the hardware comes up with a low SS. The processor datasheet reads: > Mode Fault flag -- bit sets if SS input goes low while SPI is configured = as a > master. Flag is cleared automatically by an SPI status register read (wit= h MODF > set) followed by a SPI control register 1 write. > Hence simply rereading the register is not sufficient to clear the flag. = We > redo the write also to make sure to clear the flag. >=20 > Signed-off-by: Luotao Fu Nit below, otherwise: Acked-by: Wolfram Sang > --- > drivers/spi/mpc52xx_spi.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) >=20 > diff --git a/drivers/spi/mpc52xx_spi.c b/drivers/spi/mpc52xx_spi.c > index ef8379b..5b036f2 100644 > --- a/drivers/spi/mpc52xx_spi.c > +++ b/drivers/spi/mpc52xx_spi.c > @@ -391,6 +391,7 @@ static int __devinit mpc52xx_spi_probe(struct of_devi= ce *op, > struct mpc52xx_spi *ms; > void __iomem *regs; > int rc; > + int ctrl1; u8? > =20 > /* MMIO registers */ > dev_dbg(&op->dev, "probing mpc5200 SPI device\n"); > @@ -399,7 +400,8 @@ static int __devinit mpc52xx_spi_probe(struct of_devi= ce *op, > return -ENODEV; > =20 Sidenote to all: It was tested that simply moving the read here will not su= ffice. > /* initialize the device */ > - out_8(regs+SPI_CTRL1, SPI_CTRL1_SPIE | SPI_CTRL1_SPE | SPI_CTRL1_MSTR); > + ctrl1 =3D SPI_CTRL1_SPIE | SPI_CTRL1_SPE | SPI_CTRL1_MSTR; > + out_8(regs + SPI_CTRL1, ctrl1); > out_8(regs + SPI_CTRL2, 0x0); > out_8(regs + SPI_DATADIR, 0xe); /* Set output pins */ > out_8(regs + SPI_PORTDATA, 0x8); /* Deassert /SS signal */ > @@ -409,6 +411,8 @@ static int __devinit mpc52xx_spi_probe(struct of_devi= ce *op, > * on the SPI bus. This fault will also occur if the SPI signals > * are not connected to any pins (port_config setting) */ > in_8(regs + SPI_STATUS); > + out_8(regs + SPI_CTRL1, ctrl1); > + > in_8(regs + SPI_DATA); > if (in_8(regs + SPI_STATUS) & SPI_STATUS_MODF) { > dev_err(&op->dev, "mode fault; is port_config correct?\n"); > --=20 > 1.6.5.2 >=20 > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev --=20 Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ | --pf9I7BMVVzbSWLtt Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkr6iHYACgkQD27XaX1/VRuEsQCgs+LtiJ7K5kZTTSyaEcqiRCcd MfEAn0dtprc8/tnGqncujzi5EXHPlCp9 =rlLX -----END PGP SIGNATURE----- --pf9I7BMVVzbSWLtt--