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 (with 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. > > 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(-) > > 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_device *op, > struct mpc52xx_spi *ms; > void __iomem *regs; > int rc; > + int ctrl1; u8? > > /* MMIO registers */ > dev_dbg(&op->dev, "probing mpc5200 SPI device\n"); > @@ -399,7 +400,8 @@ static int __devinit mpc52xx_spi_probe(struct of_device *op, > return -ENODEV; > Sidenote to all: It was tested that simply moving the read here will not suffice. > /* initialize the device */ > - out_8(regs+SPI_CTRL1, SPI_CTRL1_SPIE | SPI_CTRL1_SPE | SPI_CTRL1_MSTR); > + ctrl1 = 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_device *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"); > -- > 1.6.5.2 > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev -- Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ |