[PATCH] SPI: drain MXC SPI transfer buffer when probing device

[Uwe Kleine-König]

Hello Daniel,

On Thu, Nov 19, 2009 at 11:44:47AM +0100, Daniel Mack wrote:
> On the MX31litekit, the bootloader seems to communicate with the MC13783
> PMIC chip before booting Linux. However, it does not flush all the
> buffers properly after that, which makes the imx-spi driver read
> bogus data when probing the MC13783.
> 
> Fix that by draining the SPI buffer on startup.
> 
> Signed-off-by: Daniel Mack <daniel at caiaq.de>
> Cc: David Brownell <dbrownell at users.sourceforge.net>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Sascha Hauer <s.hauer at pengutronix.de>
> Cc: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
> Cc: spi-devel-general at lists.sourceforge.net
> ---
>  drivers/spi/spi_imx.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/spi/spi_imx.c b/drivers/spi/spi_imx.c
> index 89c22ef..a3894fd 100644
> --- a/drivers/spi/spi_imx.c
> +++ b/drivers/spi/spi_imx.c
> @@ -42,8 +42,11 @@
>  #define MXC_CSPITXDATA		0x04
>  #define MXC_CSPICTRL		0x08
>  #define MXC_CSPIINT		0x0c
> +#define MXC_CSPISTAT		0x14
On imx27 the register at offset 0x14 is called PERIODREG ...

>  #define MXC_RESET		0x1c
>  
> +#define MXC_CSPISTAT_RR		(1 << 3)
... and bits 0..14 are called WAIT.


> +
>  /* generic defines to abstract from the different register layouts */
>  #define MXC_INT_RR	(1 << 0) /* Receive data ready interrupt */
>  #define MXC_INT_TE	(1 << 1) /* Transmit FIFO empty interrupt */
> @@ -593,6 +596,10 @@ static int __init spi_imx_probe(struct platform_device *pdev)
>  	if (!cpu_is_mx31() || !cpu_is_mx35())
>  		writel(1, spi_imx->base + MXC_RESET);
>  
> +	/* drain the buffer */
> +	while (readl(spi_imx->base + MXC_CSPISTAT) & MXC_CSPISTAT_RR)
> +		readl(spi_imx->base + MXC_CSPIRXDATA);
> +
So this needs protection by

	if (cpu_is_mx31() || cpu_is_mx35())

(note, I didn't check the mx35 reference!).

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |