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I've tried to enable HIGHMEM to access all 512MB
of
SDRAM on a BCM1125 based board as per this previous
thread:
Using more than
256 MB of memory on SB1250 in 32-bit mode :
BCM1125 Board: XPedite3000 PrPMC
In MIPS32 mode, the memory map comes out to the
following:
Physical Memory Map:
0x00000000 - 0x0FFFFFFF
256MB
0x80000000 - 0x8FFFFFFF
256MB
Virtual Memory Map:
0x80000000 - 0x8FFFFFFF
256MB
<<<< INACCESSIBLE >>>>
256MB
My goal in enabling HIGHMEM was to get at the upper
256MB
much as described here. Access to the upper
256MB through
HIGHMEM may incur a performance hit, but it's
certainly better
going without.
However, what I get is a stall as per the log
pasted below. Enabling
CONFIG_64BIT_PHYS_ADDR does not make a
difference. Results
were cross-verified between CFE and another
bootloader.
When I hand the
physical memory described above off to add_memory_region,
I noticed a few odd things. One thing that looks
suspicious is that the variable
void *high_memory ends up
being set to 0xa0000000, or right at KSEG1,
in mm/init.c.
Also, num_physpages became huge, 0x90000, because
the init code in
kernel/setup.c and mm/init.c want a page for every
memory location, even
highmem. Is this appropriate when the memory
is not directly accessible
via __va and virt_to_phys?
This may be an ancillary effect of what's mentioned
above, but when num_physpages
grows in size, nr_free_pages doesn't track with it,
so in void vfs_caches_init(unsigned long
mempages) and the like, you get a horrible
underflow condition:
/* code */
printk("MJS - nr_free_pages():0x%X\n",
nr_free_pages());
printk("MJS - OLD mempages:0x%X\n", mempages); reserve = (mempages - nr_free_pages()) * 3/2; mempages -= reserve; printk("MJS - NEW reserve:0x%X mempages:0x%X\n", reserve, mempages); /* printout */ MJS - nr_free_pages():0x1E9A0
MJS - OLD mempages:0x90000 MJS - NEW reserve:0xAA190 mempages:0xFFFE5E70 Let me know what you think of this issue. In
anticipation of the
"Why not use MIPS64 build?" question, we'd prefer
to and will, but the
MIPS64 build has underperformed or had
bugs (SATA seek time,
networking signals, etc) that MIPS32
doesn't. For these
issues
or any case where the MIPS64 build isn't there yet,
it makes
sense to have the MIPS32 path open.
Regards,
Matt
============= Kernel Boot Log
==================
CFE version 1.0.37 for BCM91125E
(64bit,SP,BE)
Build Date: Mon Jun 28 18:33:29 CDT 2004 (mstarzewski@lsys1) Copyright (C) 2000,2001,2002,2003 Broadcom Corporation. Initializing Arena.
Initializing Devices. BCM91125E board revision 1 Config switch: 0 CPU: 1125H A2 L2 Cache: 256KB SysCfg: 00800000004A0600 [PLL_DIV: 12, IOB0_DIV: CPUCLK/4, IOB1_DIV: CPUCLK/3] CPU type 0x40103: 600MHz Total memory: 0x20000000 bytes (512MB) Total memory used by CFE: 0x8FE8AFC0 -
0x90000000 (1527872)
Initialized Data: 0x8FE8AFC0 - 0x8FE94D40 (40320) BSS Area: 0x8FE94D40 - 0x8FE95430 (1776) Local Heap: 0x8FE95430 - 0x8FF95430 (1048576) Stack Area: 0x8FF95430 - 0x8FF97430 (8192) Text (code) segment: 0x8FF97440 - 0x8FFFFFB8 (428920) Boot area (physical): 0x0FE49000 - 0x0FE89000 Relocation Factor: I:F0397440 - D:0DF8AFC0 CFE> ifconfig eth0 -addr=10.52.33.67
-mask=255.255.0.0;boot -elf
10.52.0.4:/home/mstarzewski/li
nux/kernels/mips26_works_cfe/vmlinux eth0: Link speed: 100BaseT FDX Device eth0: hwaddr 40-00-10-06-40-00, ipaddr 10.52.33.67, mask 255.255.0.0 gateway not set, nameserver not set Loader:elf Filesys:tftp Dev:eth0 File:10.52.0.4:/home/mstarzewski/linux/kernels/mips26_works_cf e/vmlinux Options:(null) Loading: 0xffffffff80100000/2558312 0xffffffff80370968/146032 Entry at 0xffffffff8032f018 Variable Name Value -------------------- -------------------------------------------------- BOOT_CONSOLE uart0 CPU_TYPE 1125H CPU_REVISION A2 CPU_NUM_CORES 1 CPU_SPEED 600 CFE_VERSION 1.0.37 CFE_BOARDNAME BCM91125E CFE_MEMORYSIZE 512 NET_DEVICE eth0 NET_IPADDR 10.52.33.67 NET_NETMASK 255.255.0.0 NET_GATEWAY 0.0.0.0 NET_NAMESERVER 0.0.0.0 BOOT_DEVICE eth0 BOOT_FILE 10.52.0.4:/home/mstarzewski/linux/kernels/mips26_works_cfe/vmlinux DELETING BOOT_CONSOLE DELETING CPU_REVISION DELETING CPU_SPEED DELETING CFE_BOARDNAME DELETING NET_DEVICE DELETING NET_NETMASK DELETING NET_NAMESERVER DELETING BOOT_FILE Variable Name Value -------------------- -------------------------------------------------- Closing network. Starting program at 0xffffffff8032f018 CFE addr:0x000000000FE8A000 size:0x0000000000000000, type:0 CFE addr:0x0000000010000000 size:0x0000000000000000, type:-2147483648 Broadcom SiByte BCM1125H A2 @ 600 MHz (SB1 rev 3) Board type: SiByte BCM91250A (SWARM) Linux version 2.6.6-rc3 (mstarzewski@lsys1) (gcc version 3.2.3 with SiByte modifications) #17 S MP Thu Dec 9 11:08:23 CST 2004 CPU revision is: 00040103 FPU revision is: 000f0103 This kernel optimized for board runs with CFE Determined physical RAM map: memory: 0fe89e00 @ 00000000 (usable) memory: 0ffffe00 @ 80000000 (usable) 1791MB HIGHMEM available. On node 0 totalpages: 589823 DMA zone: 131072 pages, LIFO batch:16 Normal zone: 0 pages, LIFO batch:1 HighMem zone: 458751 pages, LIFO batch:16 Built 1 zonelists Kernel command line: root=/dev/nfs ip=auto rw PID hash table entries: 4096 (order 12: 32768 bytes) Memory: 495040k/260644k available (1850k kernel code, 27020k reserved, 382k data, 264k init, 26 2140k highmem) Calibrating delay loop... 399.36 BogoMIPS << STALL
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