[POWERPC] Avoid unpaired stwcx. on some processors
Becky Bruce [Fri, 9 Nov 2007 22:17:49 +0000 (09:17 +1100)]
The context switch code in the kernel issues a dummy stwcx. to clear the
reservation, as recommended by the architecture.  However, some processors
can have issues if this stwcx to address A occurs while the reservation
is already held to a different address B.  To avoid this problem, the dummy
stwcx. needs to be paired with a dummy lwarx to the same address.

This adds the dummy lwarx, and creates a cpu feature bit to indicate
which cpus are affected.  Tested on mpc8641_hpcn_defconfig in
arch/powerpc; build tested in arch/ppc.

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/entry_32.S
arch/ppc/kernel/entry.S
include/asm-powerpc/cputable.h

index a7572cf..69a91bd 100644 (file)
@@ -251,6 +251,9 @@ syscall_exit_cont:
        bne-    2f
 1:
 #endif /* CONFIG_44x */
+BEGIN_FTR_SECTION
+       lwarx   r7,0,r1
+END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
        stwcx.  r0,0,r1                 /* to clear the reservation */
        lwz     r4,_LINK(r1)
        lwz     r5,_CCR(r1)
@@ -717,6 +720,9 @@ restore:
        mtctr   r11
 
        PPC405_ERR77(0,r1)
+BEGIN_FTR_SECTION
+       lwarx   r11,0,r1
+END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
        stwcx.  r0,0,r1                 /* to clear the reservation */
 
 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
index b19bfef..59e77eb 100644 (file)
@@ -251,6 +251,9 @@ syscall_exit_cont:
        bne-    2f
 1:
 #endif /* CONFIG_44x */
+BEGIN_FTR_SECTION
+       lwarx   r7,0,r1
+END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
        stwcx.  r0,0,r1                 /* to clear the reservation */
        lwz     r4,_LINK(r1)
        lwz     r5,_CCR(r1)
@@ -713,6 +716,9 @@ restore:
        mtctr   r11
 
        PPC405_ERR77(0,r1)
+BEGIN_FTR_SECTION
+       lwarx   r11,0,r1
+END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
        stwcx.  r0,0,r1                 /* to clear the reservation */
 
 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
index 9d74338..4525c78 100644 (file)
@@ -138,6 +138,7 @@ extern void do_feature_fixups(unsigned long value, void *fixup_start,
 #define CPU_FTR_FPU_UNAVAILABLE                ASM_CONST(0x0000000000800000)
 #define CPU_FTR_UNIFIED_ID_CACHE       ASM_CONST(0x0000000001000000)
 #define CPU_FTR_SPE                    ASM_CONST(0x0000000002000000)
+#define CPU_FTR_NEED_PAIRED_STWCX      ASM_CONST(0x0000000004000000)
 
 /*
  * Add the 64-bit processor unique features in the top half of the word;
@@ -261,25 +262,25 @@ extern void do_feature_fixups(unsigned long value, void *fixup_start,
 #define CPU_FTRS_7450_20       (CPU_FTR_COMMON | \
            CPU_FTR_USE_TB | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
-           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
+           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE | CPU_FTR_NEED_PAIRED_STWCX)
 #define CPU_FTRS_7450_21       (CPU_FTR_COMMON | \
            CPU_FTR_USE_TB | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_L3_DISABLE_NAP | \
-           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
+           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE | CPU_FTR_NEED_PAIRED_STWCX)
 #define CPU_FTRS_7450_23       (CPU_FTR_COMMON | \
-           CPU_FTR_USE_TB | \
+           CPU_FTR_USE_TB | CPU_FTR_NEED_PAIRED_STWCX | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7455_1        (CPU_FTR_COMMON | \
-           CPU_FTR_USE_TB | \
+           CPU_FTR_USE_TB | CPU_FTR_NEED_PAIRED_STWCX | \
            CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | CPU_FTR_L3CR | \
            CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | CPU_FTR_HAS_HIGH_BATS | \
            CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
 #define CPU_FTRS_7455_20       (CPU_FTR_COMMON | \
-           CPU_FTR_USE_TB | \
+           CPU_FTR_USE_TB | CPU_FTR_NEED_PAIRED_STWCX | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_L3_DISABLE_NAP | \
@@ -289,31 +290,32 @@ extern void do_feature_fixups(unsigned long value, void *fixup_start,
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
+           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE | CPU_FTR_NEED_PAIRED_STWCX)
 #define CPU_FTRS_7447_10       (CPU_FTR_COMMON | \
            CPU_FTR_USE_TB | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-           CPU_FTR_NEED_COHERENT | CPU_FTR_NO_BTIC | CPU_FTR_PPC_LE)
+           CPU_FTR_NEED_COHERENT | CPU_FTR_NO_BTIC | CPU_FTR_PPC_LE | \
+           CPU_FTR_NEED_PAIRED_STWCX)
 #define CPU_FTRS_7447  (CPU_FTR_COMMON | \
            CPU_FTR_USE_TB | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_L3CR | CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
+           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE | CPU_FTR_NEED_PAIRED_STWCX)
 #define CPU_FTRS_7447A (CPU_FTR_COMMON | \
            CPU_FTR_USE_TB | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE)
+           CPU_FTR_NEED_COHERENT | CPU_FTR_PPC_LE | CPU_FTR_NEED_PAIRED_STWCX)
 #define CPU_FTRS_7448  (CPU_FTR_COMMON | \
            CPU_FTR_USE_TB | \
            CPU_FTR_MAYBE_CAN_NAP | CPU_FTR_L2CR | CPU_FTR_ALTIVEC_COMP | \
            CPU_FTR_HPTE_TABLE | CPU_FTR_SPEC7450 | \
            CPU_FTR_NAP_DISABLE_L2_PR | CPU_FTR_HAS_HIGH_BATS | \
-           CPU_FTR_PPC_LE)
+           CPU_FTR_PPC_LE | CPU_FTR_NEED_PAIRED_STWCX)
 #define CPU_FTRS_82XX  (CPU_FTR_COMMON | \
            CPU_FTR_MAYBE_CAN_DOZE | CPU_FTR_USE_TB)
 #define CPU_FTRS_G2_LE (CPU_FTR_COMMON | CPU_FTR_MAYBE_CAN_DOZE | \