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authorClifford Wolf <clifford@clifford.at>2007-07-17 04:04:06 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-17 10:23:04 -0700
commit698ca47e8dba93f4b001b06b4c7037b09ac6eb09 (patch)
tree2e1f817e847d37b7397171d7fe15dc5ee0a79d07 /drivers
parent78961a5740374a8143f8fe120300f2ed160dd276 (diff)
spi_mpc83xx.c underclocking hotfix
The MPC83xx SPI controller clock divider can divide the system clock by not more then 1024. The spi_mpc83xx driver does not check this and silently writes garbage to the SPI controller registers when asked to run at lower frequencies. I've tried to run the SPI on a 266MHz MPC8349E with 100kHz for debugging a bus problem and suddenly was confronted with a 2nd problem to debug.. ;-) The patch adds an additional check which avoids writing garbage to the SPI controller registers and warn the user about it. This might help others to avoid simmilar problems. Cc: Kumar Gala <galak@gate.crashing.org> Cc: David Brownell <david-b@pacbell.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/spi/spi_mpc83xx.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/spi/spi_mpc83xx.c b/drivers/spi/spi_mpc83xx.c
index 9cdbc12278e..bbd51bc88a6 100644
--- a/drivers/spi/spi_mpc83xx.c
+++ b/drivers/spi/spi_mpc83xx.c
@@ -158,6 +158,12 @@ static void mpc83xx_spi_chipselect(struct spi_device *spi, int value)
if ((mpc83xx_spi->sysclk / spi->max_speed_hz) >= 64) {
u8 pm = mpc83xx_spi->sysclk / (spi->max_speed_hz * 64);
+ if (pm > 0x0f) {
+ printk(KERN_WARNING "MPC83xx SPI: SPICLK can't be less then a SYSCLK/1024!\n"
+ "Requested SPICLK is %d Hz. Will use %d Hz instead.\n",
+ spi->max_speed_hz, mpc83xx_spi->sysclk / 1024);
+ pm = 0x0f;
+ }
regval |= SPMODE_PM(pm) | SPMODE_DIV16;
} else {
u8 pm = mpc83xx_spi->sysclk / (spi->max_speed_hz * 4);