The patch titled
spi_mpc83xx.c underclocking hotfix
has been added to the -mm tree. Its filename is
spi_mpc83xxc-underclocking-hotfix.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: spi_mpc83xx.c underclocking hotfix
From: Clifford Wolf <[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]>
Cc: David Brownell <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
drivers/spi/spi_mpc83xx.c | 6 ++++++
1 file changed, 6 insertions(+)
diff -puN drivers/spi/spi_mpc83xx.c~spi_mpc83xxc-underclocking-hotfix
drivers/spi/spi_mpc83xx.c
--- a/drivers/spi/spi_mpc83xx.c~spi_mpc83xxc-underclocking-hotfix
+++ a/drivers/spi/spi_mpc83xx.c
@@ -158,6 +158,12 @@ static void mpc83xx_spi_chipselect(struc
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);
_
Patches currently in -mm which might be from [EMAIL PROTECTED] are
spi_mpc83xxc-underclocking-hotfix.patch
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