Greetings,
After years of benefiting from other developers' labors (thanks!)
I think I finally have a contribution. However, I'd like to get some
feedback from the community before posting the patch.
I've been looking into the timer issues on the Asus routers as
documented, for example, in https://dev.openwrt.org/ticket/4083
and https://forum.openwrt.org/viewtopic.php?pid=107594.
As noted by others, these models appear to be underclocked
at 200MHz instead of the 240MHz that appears in comments.
This is pretty easy to verify: if you set the time using 'date' and
then read it back, you'll see that these routers lose 10 sec every
minute. I ran a test over a 24 hour period and the router lost
exactly four hours (a 16.66% error).
This problem can be remedied on the above-mentioned Asus
models with the following patch for 2.6:
--- a/build_dir/linux-brcm47xx/linux-2.6.32.10/drivers/ssb/driver_mipscore.c
+++ b/build_dir/linux-brcm47xx/linux-2.6.32.10/drivers/ssb/driver_mipscore.c
@@ -218,7 +218,7 @@
if ((pll_type == SSB_PLLTYPE_5) || (bus->chip_id == 0x5365)) {
rate = 200000000;
} else if (bus->chip_id == 0x5354) {
- rate = 240000000;
+ rate = 200000000;
} else {
rate = ssb_calc_clock_rate(pll_type, n, m);
}
--- a/build_dir/linux-brcm47xx/linux-2.6.32.10/drivers/ssb/main.c
+++ b/build_dir/linux-brcm47xx/linux-2.6.32.10/drivers/ssb/main.c
@@ -1105,7 +1105,7 @@
if (bus->chip_id == 0x5365) {
rate = 100000000;
} else if (bus->chip_id == 0x5354) {
- rate = 120000000;
+ rate = 100000000;
} else {
rate = ssb_calc_clock_rate(plltype, clkctl_n, clkctl_m);
if (plltype == SSB_PLLTYPE_3) /* 25Mhz, 2 dividers */
and the following patch for 2.4:
--- a/build_dir/linux-brcm-2.4/linux-2.4.37.9/arch/mips/bcm947xx/sbmips.c
+++ b/build_dir/linux-brcm-2.4/linux-2.4.37.9/arch/mips/bcm947xx/sbmips.c
@@ -284,7 +284,7 @@
} else if ((cc = (chipcregs_t *) sb_setcore(sbh, SB_CC, 0))) {
/* 5354 chip uses a non programmable PLL of frequency
240MHz */
if (sb_chip(sbh) == BCM5354_CHIP_ID) {
- rate = 240000000;
+ rate = 200000000;
goto out;
}
pll_type = R_REG(osh, &cc->capabilities) & CC_CAP_PLL_MASK;
--- a/build_dir/linux-brcm-2.4/linux-2.4.37.9/arch/mips/bcm947xx/hndpmu.c
+++ b/build_dir/linux-brcm-2.4/linux-2.4.37.9/arch/mips/bcm947xx/hndpmu.c
@@ -710,7 +710,7 @@
if (sb_chip (sbh) == BCM5354_CHIP_ID)
{
/* 5354 gets sb clock of 100MHz from main pll */
- return 120000000;
+ return 100000000;
}
/* Find the xtal frequency in the table */
I have a few concerns. First, if these Asus models are underclocked but
there are other routers out there that aren't, then these mods should be
applied by platform+model and I don't know how to do that.
Second, I know some changes were made to the usb system to improve its
reliability but I wonder if there may be an interaction between my
changes and the usb changes? I.e. did they compensate for a 16.66%
error in jiffies that is now corrected by my patch?
Lastly, there's a patch file in 2.6 (220-bcm5354.patch) that applies the
incorrect timer values. If my changes are accepted, they should really
go into this file. Is it OK to submit a patch to a .patch file?
Thanks, -K-
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