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spi/imx: select master mode for all channels

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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@pengutronix.de>
[ukleinek: add more verbose comment about the race]
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Sascha Hauer 2011-02-08 21:08:59 +01:00 committed by Grant Likely
parent 12e8b325f2
commit f020c39e51
1 changed files with 9 additions and 3 deletions
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12
drivers/spi/spi_imx.c
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@ -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);