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    SubjectRe: [PATCH 1/3] mpc52xx_spi: fix clearing status register
    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 <l.fu@pengutronix.de>

    Nit below, otherwise:

    Acked-by: Wolfram Sang <w.sang@pengutronix.de>

    > ---
    > 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/ |
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