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Once we touch the MTRRs in VIA disable_car(), the CPU resets. Since

Browse source 
workarounds are better than instant reboots, mangle the code so that it
only switches stacks and flushes the cache.

There are two genuine fix in there as well:
We have to switch %esp before CAR is disabled. That way, the stack is
always valid.
And one of the nastier bugs easily happening in C: We had a pointer to a
const struct, but we wanted a const pointer to a struct. This kills the
(correct) warning about that code.

Many thanks to Corey for testing countless iterations of that code.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Tested and
Acked-by: Corey Osgood <corey.osgood@gmail.com>


git-svn-id: svn://coreboot.org/repository/coreboot-v3@978 f3766cd6-281f-0410-b1cd-43a5c92072e9
This commit is contained in:
Carl-Daniel Hailfinger 2008-11-02 14:47:21 +00:00
commit 4213668ab5
2 changed files with 12 additions and 2 deletions
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1
arch/x86/stage1.c
View file

@ -263,6 +263,7 @@ void stage1_phase2(void)
#ifdef CONFIG_CONSOLE_BUFFER
/* Move the printk buffer to PRINTK_BUF_ADDR_RAM */
printk_buffer_move((void *)PRINTK_BUF_ADDR_RAM, PRINTK_BUF_SIZE_RAM);
printk(BIOS_DEBUG, "Done printk() buffer move\n");
#endif
/* Turn off Cache-As-Ram */
disable_car();

13
arch/x86/via/stage1.c
View file

@ -35,6 +35,7 @@
*/
void disable_car(void)
{
printk(BIOS_DEBUG, "disable_car entry\n");
/* Determine new global variable location. Stack organization from top
* Top 4 bytes are reserved
* Pointer to global variables
@ -42,19 +43,27 @@ void disable_car(void)
*
* Align the result to 8 bytes
*/
const struct global_vars *newlocation = (struct global_vars *)((RAM_STACK_BASE - sizeof(struct global_vars *) - sizeof(struct global_vars)) & ~0x7);
struct global_vars *const newlocation = (struct global_vars *)((RAM_STACK_BASE - sizeof(struct global_vars *) - sizeof(struct global_vars)) & ~0x7);
/* Copy global variables to new location. */
memcpy(newlocation, global_vars(), sizeof(struct global_vars));
printk(BIOS_DEBUG, "disable_car global_vars copy done\n");
/* Set the new global variable pointer. */
*(struct global_vars **)(RAM_STACK_BASE - sizeof(struct global_vars *)) = newlocation;
printk(BIOS_DEBUG, "disable_car global_vars pointer adjusted\n");
printk(BIOS_DEBUG, "entering asm code now\n");
__asm__ __volatile__(
" movl %[newesp], %%esp \n"
#if ENABLE_BROKEN_CAR_DISABLING
/* We don't need cache as ram for now on */
/* disable cache */
" movl %%cr0, %%eax \n"
" orl $(0x1<<30),%%eax \n"
" movl %%eax, %%cr0 \n"
/* The MTRR setup below causes the machine to reset. Must investigate. */
/* disable fixed mtrr from now on, it will be enabled by coreboot_ram again*/
" movl %[_SYSCFG_MSR], %%ecx \n"
" rdmsr \n"
@ -75,10 +84,10 @@ void disable_car(void)
" movl %%cr0, %%eax \n"
" andl $0x9fffffff,%%eax \n"
" movl %%eax, %%cr0 \n"
#endif
" wbinvd \n"
" movl %[newesp], %%esp \n"
" call stage1_phase3 \n"
:: [newesp] "i" (newlocation),
[_SYSCFG_MSR] "i" (SYSCFG_MSR),