On Wed, Jan 08, 2014 at 10:42:35AM +0800, Kevin Hao wrote:
> On Tue, Jan 07, 2014 at 05:46:04PM -0600, Scott Wood wrote:
> > Oh. I think it'd be more readable to do "offset = start -
> > memstart_addr" and add offset instead of subtracting it.
>
> Yes, I agree. The reason that I use "offset = memstart_addr - start" is that
> it seems "memstart_addr" is always greater than "start" when we are booting
> a kdump kernel with a kernel option like "crashkernel=64M@80M". :-)
>
> >
> > Also, offset should be phys_addr_t -- even if you don't expect to
> > support offsets greater than 4G on 32-bit, it's semantically the right
> > type to use. Plus, "int" would break if this code were ever used with
> > 64-bit.
>
> I thought about using phy_addr_t for the "offset" originally but gave it up
> for the following reasons:
> * It will not be greater than 4G.
> * We have to use the ugly #ifdef CONFIG_PHYS_64BIT in restore_to_as0().
> * Need more registers for arguments for restore_to_as0().
>
> Of course you can change it to phys_addr_t if you prefer.
Here's the diff I made when applying (also changed the subf in patch 9 to
add)
diff --git a/arch/powerpc/kernel/head_fsl_booke.S
b/arch/powerpc/kernel/head_fsl_booke.S
index 71e08df..b1f7edc 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -1251,7 +1251,7 @@ _GLOBAL(switch_to_as1)
* Restore to the address space 0 and also invalidate the tlb entry created
* by switch_to_as1.
* r3 - the tlb entry which should be invalidated
- * r4 - __pa(PAGE_OFFSET in AS0) - __pa(PAGE_OFFSET in AS1)
+ * r4 - __pa(PAGE_OFFSET in AS1) - __pa(PAGE_OFFSET in AS0)
* r5 - device tree virtual address. If r4 is 0, r5 is ignored.
*/
_GLOBAL(restore_to_as0)
@@ -1266,8 +1266,8 @@ _GLOBAL(restore_to_as0)
* so we need calculate the right jump and device tree address based
* on the offset passed by r4.
*/
- subf r9,r4,r9
- subf r5,r4,r5
+ add r9,r9,r4
+ add r5,r5,r4
2: mfmsr r7
li r8,(MSR_IS | MSR_DS)
diff --git a/arch/powerpc/mm/fsl_booke_mmu.c b/arch/powerpc/mm/fsl_booke_mmu.c
index ce0c7d7..95deb9fd 100644
--- a/arch/powerpc/mm/fsl_booke_mmu.c
+++ b/arch/powerpc/mm/fsl_booke_mmu.c
@@ -291,7 +291,8 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t
start)
* and do a second relocation.
*/
if (start != memstart_addr) {
- int n, offset = memstart_addr - start;
+ int n;
+ long offset = start - memstart_addr;
is_second_reloc = 1;
n = switch_to_as1();
@@ -299,7 +300,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t
start)
if (memstart_addr > start)
map_mem_in_cams(0x4000000, CONFIG_LOWMEM_CAM_NUM);
else
- map_mem_in_cams_addr(start, PAGE_OFFSET - offset,
+ map_mem_in_cams_addr(start, PAGE_OFFSET + offset,
0x4000000, CONFIG_LOWMEM_CAM_NUM);
restore_to_as0(n, offset, __va(dt_ptr));
/* We should never reach here */
-Scott
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