On Wed, May 09, 2012 at 06:00:10PM +0530, Shilimkar, Santosh wrote:
> On Wed, May 9, 2012 at 5:53 PM, Russell King - ARM Linux
> <[email protected]> wrote:
> > On Wed, May 09, 2012 at 02:20:28PM +0530, Shilimkar, Santosh wrote:
> >> The only change done common code is clearing 'XN' bit for DRAM
> >> region in page table entries. The other change of setting the DACR
> >> register is done in ARMv7 specific code.
> >
> > Yes, XN is an ARMv6+ thing. Before ARMv5, it was implementation defined.
> >
> > Some implementations used the bit to mean "allow writes to update the
> > cache". Other implementations labelled this bit as "should be zero"
> > while others labelled it as "should be one".
> >
> Good to know.
>
> > The upshot of this is, we know that having this bit as '1' means that
> > all the CPUs we support today work. I would be _very_ concerned to
> > change this bit to zero as we _really_ don't know how the pre-ARMv6
> > CPUs would react.
> >
> I agree.
>
> > The solution to this is pretty simple - if ARMv6+ needs a different
> > base section mapping value, then we need to extract that from the code
> > and pass in the base section mapping value.
> >
> > I'll sort out a patch later today for this.
> Great.
This works for my 4430SDP board. I haven't booted it on anything else yet.
Please can you check that this solves the issue for you? Thanks.
arch/arm/boot/compressed/head.S | 29 ++++++++++++++++++-----------
1 files changed, 18 insertions(+), 11 deletions(-)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index dc7e8ce..5ad33a4 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -567,6 +567,12 @@ __armv3_mpu_cache_on:
mcr p15, 0, r0, c7, c0, 0 @ invalidate whole cache v3
mov pc, lr
+#ifdef CONFIG_CPU_DCACHE_WRITETHROUGH
+#define CB_BITS 0x08
+#else
+#define CB_BITS 0x0c
+#endif
+
__setup_mmu: sub r3, r4, #16384 @ Page directory size
bic r3, r3, #0xff @ Align the pointer
bic r3, r3, #0x3f00
@@ -578,17 +584,14 @@ __setup_mmu: sub r3, r4, #16384 @ Page
directory size
mov r9, r0, lsr #18
mov r9, r9, lsl #18 @ start of RAM
add r10, r9, #0x10000000 @ a reasonable RAM size
- mov r1, #0x12
- orr r1, r1, #3 << 10
+ mov r1, #0x12 @ XN|U + section mapping
+ orr r1, r1, #3 << 10 @ AP=11
add r2, r3, #16384
1: cmp r1, r9 @ if virt > start of RAM
-#ifdef CONFIG_CPU_DCACHE_WRITETHROUGH
- orrhs r1, r1, #0x08 @ set cacheable
-#else
- orrhs r1, r1, #0x0c @ set cacheable, bufferable
-#endif
- cmp r1, r10 @ if virt > end of RAM
- bichs r1, r1, #0x0c @ clear cacheable, bufferable
+ cmphs r10, r1 @ && end of RAM > virt
+ bic r1, r1, #0x1c @ clear XN|U + C + B
+ orrlo r1, r1, #0x10 @ Set XN|U for non-RAM
+ orrhs r1, r1, r6 @ set RAM section settings
str r1, [r0], #4 @ 1:1 mapping
add r1, r1, #1048576
teq r0, r2
@@ -599,7 +602,7 @@ __setup_mmu: sub r3, r4, #16384 @ Page
directory size
* so there is no map overlap problem for up to 1 MB compressed kernel.
* If the execution is in RAM then we would only be duplicating the above.
*/
- mov r1, #0x1e
+ orr r1, r6, #0x04 @ ensure B is set for this
orr r1, r1, #3 << 10
mov r2, pc
mov r2, r2, lsr #20
@@ -620,6 +623,7 @@ __arm926ejs_mmu_cache_on:
__armv4_mmu_cache_on:
mov r12, lr
#ifdef CONFIG_MMU
+ mov r6, #CB_BITS | 0x12 @ U
bl __setup_mmu
mov r0, #0
mcr p15, 0, r0, c7, c10, 4 @ drain write buffer
@@ -641,6 +645,7 @@ __armv7_mmu_cache_on:
#ifdef CONFIG_MMU
mrc p15, 0, r11, c0, c1, 4 @ read ID_MMFR0
tst r11, #0xf @ VMSA
+ movne r6, #CB_BITS | 0x02 @ !XN
blne __setup_mmu
mov r0, #0
mcr p15, 0, r0, c7, c10, 4 @ drain write buffer
@@ -655,7 +660,7 @@ __armv7_mmu_cache_on:
orr r0, r0, #1 << 25 @ big-endian page tables
#endif
orrne r0, r0, #1 @ MMU enabled
- movne r1, #-1
+ movne r1, #0xfffffffd @ domain 0 = client
mcrne p15, 0, r3, c2, c0, 0 @ load page table pointer
mcrne p15, 0, r1, c3, c0, 0 @ load domain access control
#endif
@@ -668,6 +673,7 @@ __armv7_mmu_cache_on:
__fa526_cache_on:
mov r12, lr
+ mov r6, #CB_BITS | 0x12 @ U
bl __setup_mmu
mov r0, #0
mcr p15, 0, r0, c7, c7, 0 @ Invalidate whole cache
@@ -682,6 +688,7 @@ __fa526_cache_on:
__arm6_mmu_cache_on:
mov r12, lr
+ mov r6, #CB_BITS | 0x12 @ U
bl __setup_mmu
mov r0, #0
mcr p15, 0, r0, c7, c0, 0 @ invalidate whole cache v3
--
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