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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/ |[unhandled content-type:application/pgp-signature]
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