m8xx_setup.c says:
/* Force all 8xx processors to use divide by 16 processor clock. */
And at the same time it is using bus-frequency for calculating
timebase. It is okay for most setups because bus-frequency is
equal to clock-frequency.
The problem emerges when cpu frequency is > 66MHz, quoting
u-boot/cpu/mpc8xx/speed.c:
if (gd->cpu_clk <= 66000000) {
sccr_reg |= SCCR_EBDF00; /* bus division factor = 1 */
gd->bus_clk = gd->cpu_clk;
} else {
sccr_reg |= SCCR_EBDF01; /* bus division factor = 2 */
gd->bus_clk = gd->cpu_clk / 2;
}
So in case of cpu clock > 66MHz, bus_clk = cpu_clk / 2. An then, from
Linux, we calculate timebase frequency as tb_freq = bus_clk / 16,
that is cpu_clk / 2 / 16, which is wrong.
This patch fixes system time drifting problem on the EP885C board
running at 133MHz.
Signed-off-by: Anton Vorontsov <[EMAIL PROTECTED]>
---
arch/powerpc/platforms/8xx/m8xx_setup.c | 7 +------
1 files changed, 1 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/platforms/8xx/m8xx_setup.c
b/arch/powerpc/platforms/8xx/m8xx_setup.c
index 184f998..0d9f75c 100644
--- a/arch/powerpc/platforms/8xx/m8xx_setup.c
+++ b/arch/powerpc/platforms/8xx/m8xx_setup.c
@@ -111,17 +111,12 @@ void __init mpc8xx_calibrate_decr(void)
/* Processor frequency is MHz.
*/
- ppc_tb_freq = 50000000;
- if (!get_freq("bus-frequency", &ppc_tb_freq)) {
- printk(KERN_ERR "WARNING: Estimating decrementer frequency "
- "(not found)\n");
- }
- ppc_tb_freq /= 16;
ppc_proc_freq = 50000000;
if (!get_freq("clock-frequency", &ppc_proc_freq))
printk(KERN_ERR "WARNING: Estimating processor frequency "
"(not found)\n");
+ ppc_tb_freq = ppc_proc_freq / 16;
printk("Decrementer Frequency = 0x%lx\n", ppc_tb_freq);
/* Perform some more timer/timebase initialization. This used
--
1.5.2.2
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
