Commit 74016852 authored by Scott Wood's avatar Scott Wood Committed by Kumar Gala
Browse files

[POWERPC] 8xx: Work around CPU15 erratum. 



The CPU15 erratum on MPC8xx chips can cause incorrect code execution
under certain circumstances, where there is a conditional or indirect
branch in the last word of a page, with a target in the last cache line
of the next page.  This patch implements one of the suggested
workarounds, by forcing a TLB miss whenever execution crosses a page
boundary.  This is done by invalidating the pages before and after the
one being loaded into the TLB in the ITLB miss handler.

Signed-off-by: default avatarScott Wood <scottwood@freescale.com>
Signed-off-by: default avatarKumar Gala <galak@kernel.crashing.org>
parent 663edbd2

arch/powerpc/kernel/head_8xx.S

+6 −0
Original line number Diff line number Diff line
@@ -298,6 +298,12 @@ InstructionTLBMiss: 
	stw	r10, 0(r0)

	stw	r11, 4(r0)

	mfspr	r10, SPRN_SRR0	/* Get effective address of fault */

#ifdef CONFIG_8xx_CPU15

	addi	r11, r10, 0x1000

	tlbie	r11

	addi	r11, r10, -0x1000

	tlbie	r11

#endif

	DO_8xx_CPU6(0x3780, r3)

	mtspr	SPRN_MD_EPN, r10	/* Have to use MD_EPN for walk, MI_EPN can't */

	mfspr	r10, SPRN_M_TWB	/* Get level 1 table entry address */

arch/powerpc/platforms/8xx/Kconfig

+16 −0
Original line number Diff line number Diff line
@@ -100,6 +100,22 @@ config 8xx_CPU6 


	  If in doubt, say N here.



config 8xx_CPU15

	bool "CPU15 Silicon Errata"

	default y

	help

	  This enables a workaround for erratum CPU15 on MPC8xx chips.

	  This bug can cause incorrect code execution under certain

	  circumstances.  This workaround adds some overhead (a TLB miss

	  every time execution crosses a page boundary), and you may wish

	  to disable it if you have worked around the bug in the compiler

	  (by not placing conditional branches or branches to LR or CTR

	  in the last word of a page, with a target of the last cache

	  line in the next page), or if you have used some other

	  workaround.



	  If in doubt, say Y here.



choice

	prompt "Microcode patch selection"

	default NO_UCODE_PATCH