ARM: 7691/1: mm: kill unused TLB_CAN_READ_FROM_L1_CACHE and use ALT_SMP instead

Many ARMv7 cores have hardware page table walkers that can read the L1
cache. This is discoverable from the ID_MMFR3 register, although this
can be expensive to access from the low-level set_pte functions and is a
pain to cache, particularly with multi-cluster systems.

A useful observation is that the multi-processing extensions for ARMv7
require coherent table walks, meaning that we can make use of ALT_SMP
patching in proc-v7-* to patch away the cache flush safely for these
cores.

Reported-by: Albin Tonnerre <Albin.Tonnerre@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

5 files changed, 7 insertions, 7 deletions

diff --git a/arch/arm/include/asm/tlbflush.h b/arch/arm/include/asm/tlbflush.h
index 4db8c8820f0d..7a3e48dceb84 100644
--- a/arch/arm/include/asm/tlbflush.h
+++ b/arch/arm/include/asm/tlbflush.h
@@ -169,7 +169,7 @@
 # define v6wbi_always_flags     (-1UL)
 #endif
 
-#define v7wbi_tlb_flags_smp     (TLB_WB | TLB_DCLEAN | TLB_BARRIER | \
+#define v7wbi_tlb_flags_smp     (TLB_WB | TLB_BARRIER | \
                                  TLB_V7_UIS_FULL | TLB_V7_UIS_PAGE | \
                                  TLB_V7_UIS_ASID | TLB_V7_UIS_BP)
 #define v7wbi_tlb_flags_up      (TLB_WB | TLB_DCLEAN | TLB_BARRIER | \
diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S
index bcaaa8de9325..a286d4712b57 100644
--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -80,12 +80,10 @@ ENTRY(cpu_v6_do_idle)
         mov     pc, lr
 
 ENTRY(cpu_v6_dcache_clean_area)
-#ifndef TLB_CAN_READ_FROM_L1_CACHE
 1:      mcr     p15, 0, r0, c7, c10, 1          @ clean D entry
         add     r0, r0, #D_CACHE_LINE_SIZE
         subs    r1, r1, #D_CACHE_LINE_SIZE
         bhi     1b
-#endif
         mov     pc, lr
 
 /*
diff --git a/arch/arm/mm/proc-v7-2level.S b/arch/arm/mm/proc-v7-2level.S
index 78f520bc0e99..9704097c450e 100644
--- a/arch/arm/mm/proc-v7-2level.S
+++ b/arch/arm/mm/proc-v7-2level.S
@@ -110,7 +110,8 @@ ENTRY(cpu_v7_set_pte_ext)
  ARM(   str     r3, [r0, #2048]! )
  THUMB( add     r0, r0, #2048 )
  THUMB( str     r3, [r0] )
-        mcr     p15, 0, r0, c7, c10, 1          @ flush_pte
+        ALT_SMP(mov     pc,lr)
+        ALT_UP (mcr     p15, 0, r0, c7, c10, 1)         @ flush_pte
 #endif
         mov     pc, lr
 ENDPROC(cpu_v7_set_pte_ext)
diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
index 6ffd78c0f9ab..363027e811d6 100644
--- a/arch/arm/mm/proc-v7-3level.S
+++ b/arch/arm/mm/proc-v7-3level.S
@@ -73,7 +73,8 @@ ENTRY(cpu_v7_set_pte_ext)
         tst     r3, #1 << (55 - 32)             @ L_PTE_DIRTY
         orreq   r2, #L_PTE_RDONLY
 1:      strd    r2, r3, [r0]
-        mcr     p15, 0, r0, c7, c10, 1          @ flush_pte
+        ALT_SMP(mov     pc, lr)
+        ALT_UP (mcr     p15, 0, r0, c7, c10, 1)         @ flush_pte
 #endif
         mov     pc, lr
 ENDPROC(cpu_v7_set_pte_ext)
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 3a3c015f8d5c..37716b0508e1 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -75,14 +75,14 @@ ENTRY(cpu_v7_do_idle)
 ENDPROC(cpu_v7_do_idle)
 
 ENTRY(cpu_v7_dcache_clean_area)
-#ifndef TLB_CAN_READ_FROM_L1_CACHE
+        ALT_SMP(mov     pc, lr)                 @ MP extensions imply L1 PTW
+        ALT_UP(W(nop))
         dcache_line_size r2, r3
 1:      mcr     p15, 0, r0, c7, c10, 1          @ clean D entry
         add     r0, r0, r2
         subs    r1, r1, r2
         bhi     1b
         dsb
-#endif
         mov     pc, lr
 ENDPROC(cpu_v7_dcache_clean_area)