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authorClifford Wolf <clifford@clifford.at>2007-07-17 07:04:06 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-17 13:23:04 -0400
commit698ca47e8dba93f4b001b06b4c7037b09ac6eb09 (patch)
tree2e1f817e847d37b7397171d7fe15dc5ee0a79d07 /drivers/spi/spi_mpc83xx.c
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/spi/spi_mpc83xx.c')
-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 9cdbc12278e5..bbd51bc88a60 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)
158 158
159 if ((mpc83xx_spi->sysclk / spi->max_speed_hz) >= 64) { 159 if ((mpc83xx_spi->sysclk / spi->max_speed_hz) >= 64) {
160 u8 pm = mpc83xx_spi->sysclk / (spi->max_speed_hz * 64); 160 u8 pm = mpc83xx_spi->sysclk / (spi->max_speed_hz * 64);
161 if (pm > 0x0f) {
162 printk(KERN_WARNING "MPC83xx SPI: SPICLK can't be less then a SYSCLK/1024!\n"
163 "Requested SPICLK is %d Hz. Will use %d Hz instead.\n",
164 spi->max_speed_hz, mpc83xx_spi->sysclk / 1024);
165 pm = 0x0f;
166 }
161 regval |= SPMODE_PM(pm) | SPMODE_DIV16; 167 regval |= SPMODE_PM(pm) | SPMODE_DIV16;
162 } else { 168 } else {
163 u8 pm = mpc83xx_spi->sysclk / (spi->max_speed_hz * 4); 169 u8 pm = mpc83xx_spi->sysclk / (spi->max_speed_hz * 4);