[PATCH] spi/imx: select master mode for all channels

[Grant Likely]

2011/2/15 Grant Likely <grant.likely at secretlab.ca>:
> On Tue, Feb 08, 2011 at 09:08:59PM +0100, Uwe Kleine-König wrote:
>> From: Sascha Hauer <s.hauer at pengutronix.de>
>>
>> The hardware seems to have a race condition when the inactive
>> channels are in slave mode. We support master mode only, so
>> we can just switch all channels to master mode.
>>
>> Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
>> [ukleinek: add more verbose comment about the race]
>> Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
>> ---
>> Hello,
>>
>> maybe one of our friends at Freescale can comment?
>
> Any feedback on this one?  Or should I just merge it?

I've gone ahead and merged it.  I can pull it back out if anyone
complains though.

Thanks,

g.

>
> g.
>
>>
>> Best regards
>> Uwe
>>
>>  drivers/spi/spi_imx.c |   12 +++++++++---
>>  1 files changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/spi/spi_imx.c b/drivers/spi/spi_imx.c
>> index 1cf9d5f..69d6dba 100644
>> --- a/drivers/spi/spi_imx.c
>> +++ b/drivers/spi/spi_imx.c
>> @@ -174,7 +174,7 @@ static unsigned int spi_imx_clkdiv_2(unsigned int fin,
>>  #define SPI_IMX2_3_CTRL              0x08
>>  #define SPI_IMX2_3_CTRL_ENABLE               (1 <<  0)
>>  #define SPI_IMX2_3_CTRL_XCH          (1 <<  2)
>> -#define SPI_IMX2_3_CTRL_MODE(cs)     (1 << ((cs) +  4))
>> +#define SPI_IMX2_3_CTRL_MODE_MASK    (0xf << 4)
>>  #define SPI_IMX2_3_CTRL_POSTDIV_OFFSET       8
>>  #define SPI_IMX2_3_CTRL_PREDIV_OFFSET        12
>>  #define SPI_IMX2_3_CTRL_CS(cs)               ((cs) << 18)
>> @@ -253,8 +253,14 @@ static int __maybe_unused spi_imx2_3_config(struct spi_imx_data *spi_imx,
>>  {
>>       u32 ctrl = SPI_IMX2_3_CTRL_ENABLE, cfg = 0;
>>
>> -     /* set master mode */
>> -     ctrl |= SPI_IMX2_3_CTRL_MODE(config->cs);
>> +     /*
>> +      * The hardware seems to have a race condition when changing modes. The
>> +      * current assumption is that the selection of the channel arrives
>> +      * earlier in the hardware than the mode bits when they are written at
>> +      * the same time.
>> +      * So set master mode for all channels as we do not support slave mode.
>> +      */
>> +     ctrl |= SPI_IMX2_3_CTRL_MODE_MASK;
>>
>>       /* set clock speed */
>>       ctrl |= spi_imx2_3_clkdiv(spi_imx->spi_clk, config->speed_hz);
>> --
>> 1.7.2.3
>>
>>
>> ------------------------------------------------------------------------------
>> The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE:
>> Pinpoint memory and threading errors before they happen.
>> Find and fix more than 250 security defects in the development cycle.
>> Locate bottlenecks in serial and parallel code that limit performance.
>> http://p.sf.net/sfu/intel-dev2devfeb
>> _______________________________________________
>> spi-devel-general mailing list
>> spi-devel-general at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/spi-devel-general
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.