Author: wmb
Date: 2007-08-30 22:13:18 +0200 (Thu, 30 Aug 2007)
New Revision: 585
Modified:
cpu/x86/pc/olpc/rmstart.fth
Log:
rmstart.fth - Added commentary describing the code that turns of the MIC bias.
Modified: cpu/x86/pc/olpc/rmstart.fth
===================================================================
--- cpu/x86/pc/olpc/rmstart.fth 2007-08-28 23:18:26 UTC (rev 584)
+++ cpu/x86/pc/olpc/rmstart.fth 2007-08-30 20:13:18 UTC (rev 585)
@@ -128,6 +128,11 @@
h# 01 # al mov al h# 80 # out
+ \ The following code sequence is a workaround for a hardware situation.
+ \ The MIC-on LED defaults to "on", because the CODEC chip powers on with
+ \ VREFOUT (i.e. MIC vbias) on. We don't want the MIC LED to turn on
+ \ automatically on every resume, so we have to turn it off very quickly.
+
\ The next few MSRs allow us to access the 5536
\ EXTMSR - page 449 \ Use PCI device #F for port 2
@@ -141,18 +146,21 @@
op: h# 51000010 # cx mov \ MSR number - CPU interface serial
wrmsr
- op: h# 014fc001 # dx mov
- op: h# 01480001 # ax mov
- op: h# 51000026 # cx mov
+ op: h# 014fc001 # dx mov \ Top of I/O region - 0x14fc, I/O space
+ op: h# 01480001 # ax mov \ Bottom of I/O region - 0x1480, enable
+ op: h# 51000026 # cx mov \ Region 6 configuration
wrmsr
- op: h# a0000001 # dx mov
- op: h# 480fff80 # ax mov
- op: h# 510100e1 # cx mov
+ op: h# a0000001 # dx mov \ Maps I/O space starting at 0x1480
+ op: h# 480fff80 # ax mov \ to the AC97 CODEC (ACC block)
+ op: h# 510100e1 # cx mov \ IOD Base Mask 1 MSR
wrmsr
+ \ Writes 4 to CODEC register 0x76 to turn off VBIAS (VREFOUT)
op: h# 7601.0004 # ax mov op: h# 148c # dx mov op: ax dx out
+ \ End of MIC LED code.
+
\ This code is highly optimized because it runs when the CPU is in
\ it slowest operation mode, so we want to get it done fast.
\ GLCP_SYS_RSTPLL - page 406
This may look right, but it is a bad kludge. Open Firmware, when "biosload"ed,
expects a top-of-RAM at physical address 0x1004 ( mem-info-pa 4 + ) , as a
little endian pointer. LinuxBIOS however only provides its tables. There's
currently code in the queue from Jens Freimann to parse the LB tables, and
OFW should ideally get its info from that, but the stuff is not yet stable
(right, Jens?) and providing the table info to the /memory device init is
still to be written.
Until openfirmware/cpu/x86/pc/biosload/probemem.fth is changed or maybe even
an openfirmware/cpu/x86/pc/linuxbiosload is created, use this evil hack. The
memory map is parsed anyway to find a RAM buffer for the payload, so I just
hook in here to find a 32-bit pointer to the top of RAM, clipped to 3GB, to
not confuse the payload :)
Signed-off-by: Torsten Duwe <duwe(a)lst.de>
Recommendation: do _NOT_ apply!
I admit that I wrote this, but only as an interim solution.
As on http://www.openbios.org/Open_Firmware, change the config to get a
suitable ELF header. qemu-loaded is also necessary on real hardware for
current openfirmware versions. pc-linux will get you the capability to load
ELF kernels from EXT2 file systems :-)
virtual-mode somehow doesn't work for me.
Signed-off-by: Torsten Duwe <duwe(a)lst.de>
Recommendation: update the wiki page
Hi all!
Working a little on $SUBJECT, I found a few patches to be necessary to get it
all running. It's far from perfect yet, but I wanted to share with you what
I found so far.
I had to make the config change to Open Firmware similar to that on the
openbios wiki, and change 4 things in the LinuxBIOS source. I'll post these
to the individual lists now.
Thanks a lot for the work I could build upon!
Torsten
As on http://www.openbios.org/Open_Firmware, change the config to get a
suitable ELF header. qemu-loaded is also necessary on real hardware for
current openfirmware versions. pc-linux will get you the capability to load
ELF kernels from EXT2 file systems :-)
virtual-mode somehow doesn't work for me.
Recommendation: update the wiki page
