[coreboot] GeodeLX RAM initialisation issue

Nathan Williams nathan at traverse.com.au
Mon Nov 23 08:27:35 CET 2009

Marc Jones wrote:
> On Tue, Nov 10, 2009 at 1:26 PM, Nathan Williams <nathan at traverse.com.au> wrote:
>> Marc Jones wrote:
>>> On Fri, Nov 6, 2009 at 7:57 AM, Nathan Williams <nathan at traverse.com.au>
>>> wrote:
>>>> Another observation I made was that by setting the debug_level to
>>>> instead of dying at the usual spot in disable_car() and stopping,
>>>> coreboot
>>>> would reset continuously (cycling every 1-2 seconds)
>> Since I needed to have a BIOS that didn't have much debugging enabled for a
>> customer sample, I looked a bit deeper to find the cause of this continuous
>> reset behaviour.  Even changing the debug level from BIOS_SPEW to BIOS_DEBUG
>> caused the reset.  I tracked it down to a single  printk and my attached
>> patch means it works at BIOS_CRIT now, just with a few extra debug lines.
>>  Without the printk, the code gets to "missing phase4_read_resources" (just
>> a few lines down from my patch) before restarting.
> This sounds like it is probably blowing the stack or the stack hits
> memory that isn't working correctly.
>>>> Another issue that's partly related is the ability for coreboot to set
>>>>  the
>>>> GeodeLink speed depending on the detected RAM speed.  As a work-around,
>>>> we
>>>> are only using 333MHz SODIMMs and have set the bootstrap bits for
>>>> GLCP_SYS_RSTPLL[7:1] (section of LX databook) to 500Mhz CPU,
>>>> 333MHz GLIU instead of bypass mode.  In bypass mode, the GLIU is 266MHz
>>>> and
>>>> some of our 333MHz RAM will fail in disable_car(). As a test, I have
>>>> experimented with
>>>> pll_reset(MANUALCONF, PLLMSRHI, PLLMSRLO) in initram.c in an attempt to
>>>> change the GLIU to 333MHz.  I probably didn't have the correct bits set,
>>>> so
>>>> even though I managed to set GLIU, it failed the last test (DLL) in
>>>> sdram_enable() and would reset.
>>> Your second problem might explain the first. You should look closely
>>> at the detection problem. It depends on the reset and the state of the
>>> rstpll flags. There could be a corner case or something unusual going
>>> on. How did you set the boot strap bits with hardware (straps)? You
>>> should use pll_reset(ManualConf) settings to change it with hardware.
>>> Marc
>> Sorry, I should have explained that we set the boostrap bits in hardware:
>> Bit 7: PW1 pad - active high when the PCI clock is 66 MHz, low for 33 MHz.
>> Bit 6: IRQ13 pad - active high for stall-on-reset debug feature, otherwise
>> low.
>> Bit 5: PW0 pad - part of CPU/GLIU frequency selects.
>> Bit 4: SUSPA# pad - part of CPU/GLIU frequency selects.
>> Bit 3: GNT2# pad - part of CPU/GLIU frequency selects.
>> Bit 2: GNT1# pad - part of CPU/GLIU frequency selects.
>> Bit 1: GNT0# pad - part of CPU/GLIU frequency selects.
>> We have pulled these pins up or down to be "0010110", which corresponds to
>> CPU 500MHz, GLIU 333MHz in table 6-87.  This should also mean that the on
>> reset, the value of GLCP_SYS_RSTPLL should be 0000049C_0300182Ch (except
>> that SWFLAGS (GLCP_SYS_RSTPLL[31:26]) is only reset to 0 on Power On Reset
>> (POR).  So I should be using pll_reset(ManualConf)?  I'll try it later today
>> and see if I can get some debugging output.
> If it is set by straps, it should be doing the right thing and you
> don't need to use the ManualConf. There could still be a corner case
> and you should try trace through the soft reset that is causing the
> problem. Also, have you diff'd the MC settings between the BIOS and
> coreboot. I would be interested in discrepancies.
> Marc

I managed to get the commercial BIOS to boot on my board and diffed it with coreboot:


The only differences I can see are related to interrupts, which shouldn't matter in relation to
my RAM problems.

I have also run a memtest86 with the commercial BIOS (from bootable CDROM) and as a payload in coreboot.
The commercial BIOS didn't have any errors, but my coreboot did.  So the hardware can't be too bad.


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