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powerpc: Cleanup handling of the DSCR bit in the FSCR register

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As suggested by paulus we can simplify the Data Stream Control Register
(DSCR) Facility Status and Control Register (FSCR) handling.

Firstly, we simplify the asm by using a rldimi.

Secondly, we now use the FSCR only to control the DSCR facility, rather
than both the FSCR and HFSCR.  Users will see no functional change from
this but will get a minor speedup as they will trap into the kernel only
once (rather than twice) when they first touch the DSCR.  Also, this
changes removes a bunch of ugly FTR_SECTION code.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Neuling 2013-08-26 13:55:57 +10:00 committed by Benjamin Herrenschmidt
parent 3f1f431188
commit bc683a7e51
2 changed files with 8 additions and 30 deletions
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31
arch/powerpc/kernel/entry_64.S
View File

@ -578,34 +578,15 @@ BEGIN_FTR_SECTION
ld r7,DSCR_DEFAULT@toc(2)
ld r0,THREAD_DSCR(r4)
cmpwi r6,0
li r8, FSCR_DSCR
bne 1f
ld r0,0(r7)
b 3f
1:
BEGIN_FTR_SECTION_NESTED(70)
mfspr r6, SPRN_FSCR
or r6, r6, r8
mtspr SPRN_FSCR, r6
BEGIN_FTR_SECTION_NESTED(69)
mfspr r6, SPRN_HFSCR
or r6, r6, r8
mtspr SPRN_HFSCR, r6
END_FTR_SECTION_NESTED(CPU_FTR_HVMODE, CPU_FTR_HVMODE, 69)
b 4f
END_FTR_SECTION_NESTED(CPU_FTR_ARCH_207S, CPU_FTR_ARCH_207S, 70)
3:
BEGIN_FTR_SECTION_NESTED(70)
mfspr r6, SPRN_FSCR
andc r6, r6, r8
mtspr SPRN_FSCR, r6
BEGIN_FTR_SECTION_NESTED(69)
mfspr r6, SPRN_HFSCR
andc r6, r6, r8
mtspr SPRN_HFSCR, r6
END_FTR_SECTION_NESTED(CPU_FTR_HVMODE, CPU_FTR_HVMODE, 69)
END_FTR_SECTION_NESTED(CPU_FTR_ARCH_207S, CPU_FTR_ARCH_207S, 70)
4: cmpd r0,r25
BEGIN_FTR_SECTION_NESTED(70)
mfspr r8, SPRN_FSCR
rldimi r8, r6, FSCR_DSCR_LG, (63 - FSCR_DSCR_LG)
mtspr SPRN_FSCR, r8
END_FTR_SECTION_NESTED(CPU_FTR_ARCH_207S, CPU_FTR_ARCH_207S, 70)
cmpd r0,r25
beq 2f
mtspr SPRN_DSCR,r0
2:

7
arch/powerpc/kernel/traps.c
View File

@ -1342,13 +1342,10 @@ void facility_unavailable_exception(struct pt_regs *regs)
if (status == FSCR_DSCR_LG) {
/* User is acessing the DSCR. Set the inherit bit and allow
* the user to set it directly in future by setting via the
* H/FSCR DSCR bit.
* FSCR DSCR bit. We always leave HFSCR DSCR set.
*/
current->thread.dscr_inherit = 1;
if (hv)
mtspr(SPRN_HFSCR, value | HFSCR_DSCR);
else
mtspr(SPRN_FSCR, value | FSCR_DSCR);
mtspr(SPRN_FSCR, value | FSCR_DSCR);
return;
}