[RFC][PATCH v3] powerpc: e300c2/c3/c4 TLB errata workaround
Benjamin Herrenschmidt
benh at kernel.crashing.org
Sat Mar 14 08:25:19 EST 2009
On Fri, 2009-03-13 at 10:16 -0500, Kumar Gala wrote:
> From: David Jander <david.jander at protonic.nl>
>
> Complete workaround for DTLB errata in e300c2/c3/c4 processors.
>
> Due to the bug, the hardware-implemented LRU algorythm always goes to way
> 1 of the TLB. This fix implements the proposed software workaround in
> form of a LRW table for chosing the TLB-way.
>
> Signed-off-by: David Jander <david at protonic.nl>
> Signed-off-by: Kumar Gala <galak at kernel.crashing.org>
> ---
>
> Added cpu feature support.. need to check with Ben if we should use a MMU feature instead
Yes, we should...
Cheers,
Ben.
> - k
>
> arch/powerpc/include/asm/cputable.h | 7 +++-
> arch/powerpc/kernel/cputable.c | 4 +-
> arch/powerpc/kernel/head_32.S | 61 +++++++++++++++++++++++++++++++++++
> 3 files changed, 69 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
> index fca1611..42e3145 100644
> --- a/arch/powerpc/include/asm/cputable.h
> +++ b/arch/powerpc/include/asm/cputable.h
> @@ -152,6 +152,7 @@ extern const char *powerpc_base_platform;
> #define CPU_FTR_NAP_DISABLE_L2_PR ASM_CONST(0x0000000000002000)
> #define CPU_FTR_DUAL_PLL_750FX ASM_CONST(0x0000000000004000)
> #define CPU_FTR_NO_DPM ASM_CONST(0x0000000000008000)
> +#define CPU_FTR_NEED_DTLB_SW_LRU ASM_CONST(0x0000000000010000)
> #define CPU_FTR_NEED_COHERENT ASM_CONST(0x0000000000020000)
> #define CPU_FTR_NO_BTIC ASM_CONST(0x0000000000040000)
> #define CPU_FTR_NODSISRALIGN ASM_CONST(0x0000000000100000)
> @@ -356,7 +357,11 @@ extern const char *powerpc_base_platform;
> CPU_FTR_COMMON)
> #define CPU_FTRS_E300C2 (CPU_FTR_MAYBE_CAN_DOZE | \
> CPU_FTR_USE_TB | CPU_FTR_MAYBE_CAN_NAP | \
> - CPU_FTR_COMMON | CPU_FTR_FPU_UNAVAILABLE)
> + CPU_FTR_COMMON | CPU_FTR_FPU_UNAVAILABLE | \
> + CPU_FTR_NEED_DTLB_SW_LRU)
> +#define CPU_FTRS_E300C3 (CPU_FTR_MAYBE_CAN_DOZE | \
> + CPU_FTR_USE_TB | CPU_FTR_MAYBE_CAN_NAP | \
> + CPU_FTR_COMMON | CPU_FTR_NEED_DTLB_SW_LRU)
> #define CPU_FTRS_CLASSIC32 (CPU_FTR_COMMON | CPU_FTR_USE_TB)
> #define CPU_FTRS_8XX (CPU_FTR_USE_TB)
> #define CPU_FTRS_40X (CPU_FTR_USE_TB | CPU_FTR_NODSISRALIGN | CPU_FTR_NOEXECUTE)
> diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
> index ccea243..039452c 100644
> --- a/arch/powerpc/kernel/cputable.c
> +++ b/arch/powerpc/kernel/cputable.c
> @@ -1101,7 +1101,7 @@ static struct cpu_spec __initdata cpu_specs[] = {
> .pvr_mask = 0x7fff0000,
> .pvr_value = 0x00850000,
> .cpu_name = "e300c3",
> - .cpu_features = CPU_FTRS_E300,
> + .cpu_features = CPU_FTRS_E300C3,
> .cpu_user_features = COMMON_USER,
> .mmu_features = MMU_FTR_USE_HIGH_BATS,
> .icache_bsize = 32,
> @@ -1116,7 +1116,7 @@ static struct cpu_spec __initdata cpu_specs[] = {
> .pvr_mask = 0x7fff0000,
> .pvr_value = 0x00860000,
> .cpu_name = "e300c4",
> - .cpu_features = CPU_FTRS_E300,
> + .cpu_features = CPU_FTRS_E300C3,
> .cpu_user_features = COMMON_USER,
> .mmu_features = MMU_FTR_USE_HIGH_BATS,
> .icache_bsize = 32,
> diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
> index f8c2e6b..eecae0d 100644
> --- a/arch/powerpc/kernel/head_32.S
> +++ b/arch/powerpc/kernel/head_32.S
> @@ -554,6 +554,10 @@ DataLoadTLBMiss:
> * r2: ptr to linux-style pte
> * r3: scratch
> */
> +BEGIN_FTR_SECTION
> + b TlbWo /* Code for TLB-errata workaround doesn't fit here */
> +END_FTR_SECTION_IFSET(CPU_FTR_NEED_DTLB_SW_LRU)
> +RFTlbWo:
> mfctr r0
> /* Get PTE (linux-style) and check access */
> mfspr r3,SPRN_DMISS
> @@ -626,6 +630,31 @@ DataStoreTLBMiss:
> * r2: ptr to linux-style pte
> * r3: scratch
> */
> +BEGIN_FTR_SECTION
> +/* MPC512x: workaround for errata in die M36P and earlier:
> + * Implement LRW for TLB way.
> + */
> + mfspr r3,SPRN_DMISS
> + rlwinm r3,r3,19,25,29 /* Get Address bits 19:15 */
> + lis r2,lrw at ha /* Search index in lrw[] */
> + addi r2,r2,lrw at l
> + tophys(r2,r2)
> + lwzx r1,r3,r2 /* Get item from lrw[] */
> + cmpwi 0,r1,0 /* Was it way 0 last time? */
> + beq- 0,113f /* Then goto 113: */
> +
> + mfspr r1,SPRN_SRR1
> + rlwinm r1,r1,0,15,13 /* Mask out SRR1[WAY] */
> + mtspr SPRN_SRR1,r1
> +
> + li r0,0
> + stwx r0,r3,r2 /* Make lrw[] entry 0 */
> + b 114f
> +113:
> + li r0,1
> + stwx r0,r3,r2 /* Make lrw[] entry 1 */
> +114:
> +END_FTR_SECTION_IFSET(CPU_FTR_NEED_DTLB_SW_LRU)
> mfctr r0
> /* Get PTE (linux-style) and check access */
> mfspr r3,SPRN_DMISS
> @@ -813,6 +842,32 @@ giveup_altivec:
> blr
> #endif /* CONFIG_ALTIVEC */
>
> +TlbWo:
> +/* MPC512x: workaround for errata in die M36P and earlier:
> + * Implement LRW for TLB way.
> + */
> + mfspr r3,SPRN_DMISS
> + rlwinm r3,r3,19,25,29 /* Get Address bits 19:15 */
> + lis r2,lrw at ha /* Search index in lrw[] */
> + addi r2,r2,lrw at l
> + tophys(r2,r2)
> + lwzx r1,r3,r2 /* Get item from lrw[] */
> + cmpwi 0,r1,0 /* Was it way 0 last time? */
> + beq- 0,113f /* Then goto 113: */
> +
> + mfspr r1,SPRN_SRR1
> + rlwinm r1,r1,0,15,13 /* Mask out SRR1[WAY] */
> + mtspr SPRN_SRR1,r1
> +
> + li r0,0
> + stwx r0,r3,r2 /* Make lrw[] entry 0 */
> + b 114f
> +113:
> + li r0,1
> + stwx r0,r3,r2 /* Make lrw[] entry 1 */
> +114:
> + b RFTlbWo
> +
> /*
> * This code is jumped to from the startup code to copy
> * the kernel image to physical address PHYSICAL_START.
> @@ -1328,6 +1383,12 @@ intercept_table:
> .long 0, 0, 0, 0, 0, 0, 0, 0
> .long 0, 0, 0, 0, 0, 0, 0, 0
>
> +lrw:
> + .long 0, 0, 0, 0, 0, 0, 0, 0
> + .long 0, 0, 0, 0, 0, 0, 0, 0
> + .long 0, 0, 0, 0, 0, 0, 0, 0
> + .long 0, 0, 0, 0, 0, 0, 0, 0
> +
> /* Room for two PTE pointers, usually the kernel and current user pointers
> * to their respective root page table.
> */
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