ARM: 7773/1: PJ4B: Add support for errata 4742

This commit fixes the regression on Armada 370 (the kernal hang during
boot) introduced by the commit: "ARM: 7691/1: mm: kill unused
TLB_CAN_READ_FROM_L1_CACHE and use ALT_SMP instead".

When coming out of either a Wait for Interrupt (WFI) or a Wait for
Event (WFE) IDLE states, a specific timing sensitivity exists between
the retiring WFI/WFE instructions and the newly issued subsequent
instructions. This sensitivity can result in a CPU hang scenario.  The
workaround is to insert either a Data Synchronization Barrier (DSB) or
Data Memory Barrier (DMB) command immediately after the WFI/WFE
instruction.

This commit was based on the work of Lior Amsalem, but heavily
modified to apply the errata fix dynamically according to the
processor type thanks to the suggestions of Russell King and Nicolas
Pitre.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Tested-by: Willy Tarreau <w@1wt.eu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

4 files changed, 59 insertions, 3 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 2651b1da1c56..136f263ed47b 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1087,6 +1087,20 @@ if !MMU
 source "arch/arm/Kconfig-nommu"
 endif
 
+config PJ4B_ERRATA_4742
+        bool "PJ4B Errata 4742: IDLE Wake Up Commands can Cause the CPU Core to Cease Operation"
+        depends on CPU_PJ4B && MACH_ARMADA_370
+        default y
+        help
+          When coming out of either a Wait for Interrupt (WFI) or a Wait for
+          Event (WFE) IDLE states, a specific timing sensitivity exists between
+          the retiring WFI/WFE instructions and the newly issued subsequent
+          instructions.  This sensitivity can result in a CPU hang scenario.
+          Workaround:
+          The software must insert either a Data Synchronization Barrier (DSB)
+          or Data Memory Barrier (DMB) command immediately after the WFI/WFE
+          instruction
+
 config ARM_ERRATA_326103
         bool "ARM errata: FSR write bit incorrect on a SWP to read-only memory"
         depends on CPU_V6
diff --git a/arch/arm/include/asm/glue-proc.h b/arch/arm/include/asm/glue-proc.h
index ac1dd54724b6..8017e94acc5e 100644
--- a/arch/arm/include/asm/glue-proc.h
+++ b/arch/arm/include/asm/glue-proc.h
@@ -230,6 +230,15 @@
 # endif
 #endif
 
+#ifdef CONFIG_CPU_PJ4B
+# ifdef CPU_NAME
+#  undef  MULTI_CPU
+#  define MULTI_CPU
+# else
+#  define CPU_NAME cpu_pj4b
+# endif
+#endif
+
 #ifndef MULTI_CPU
 #define cpu_proc_init                   __glue(CPU_NAME,_proc_init)
 #define cpu_proc_fin                    __glue(CPU_NAME,_proc_fin)
diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index f9a0aa725ea9..e3c48a3fe063 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S
@@ -333,3 +333,8 @@ ENTRY(\name\()_tlb_fns)
         .endif
         .size   \name\()_tlb_fns, . - \name\()_tlb_fns
 .endm
+
+.macro globl_equ x, y
+        .globl  \x
+        .equ    \x, \y
+.endm
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 4c8c9c10a388..e35fec34453e 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -140,6 +140,29 @@ ENTRY(cpu_v7_do_resume)
 ENDPROC(cpu_v7_do_resume)
 #endif
 
+#ifdef CONFIG_CPU_PJ4B
+        globl_equ       cpu_pj4b_switch_mm,     cpu_v7_switch_mm
+        globl_equ       cpu_pj4b_set_pte_ext,   cpu_v7_set_pte_ext
+        globl_equ       cpu_pj4b_proc_init,     cpu_v7_proc_init
+        globl_equ       cpu_pj4b_proc_fin,      cpu_v7_proc_fin
+        globl_equ       cpu_pj4b_reset,         cpu_v7_reset
+#ifdef CONFIG_PJ4B_ERRATA_4742
+ENTRY(cpu_pj4b_do_idle)
+        dsb                                     @ WFI may enter a low-power mode
+        wfi
+        dsb                                     @barrier
+        mov     pc, lr
+ENDPROC(cpu_pj4b_do_idle)
+#else
+        globl_equ       cpu_pj4b_do_idle,       cpu_v7_do_idle
+#endif
+        globl_equ       cpu_pj4b_dcache_clean_area,     cpu_v7_dcache_clean_area
+        globl_equ       cpu_pj4b_do_suspend,    cpu_v7_do_suspend
+        globl_equ       cpu_pj4b_do_resume,     cpu_v7_do_resume
+        globl_equ       cpu_pj4b_suspend_size,  cpu_v7_suspend_size
+
+#endif
+
         __CPUINIT
 
 /*
@@ -350,6 +373,9 @@ __v7_setup_stack:
 
         @ define struct processor (see <asm/proc-fns.h> and proc-macros.S)
         define_processor_functions v7, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
+#ifdef CONFIG_CPU_PJ4B
+        define_processor_functions pj4b, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
+#endif
 
         .section ".rodata"
 
@@ -362,7 +388,7 @@ __v7_setup_stack:
         /*
          * Standard v7 proc info content
          */
-.macro __v7_proc initfunc, mm_mmuflags = 0, io_mmuflags = 0, hwcaps = 0
+.macro __v7_proc initfunc, mm_mmuflags = 0, io_mmuflags = 0, hwcaps = 0, proc_fns = v7_processor_functions
         ALT_SMP(.long   PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AP_READ | \
                         PMD_SECT_AF | PMD_FLAGS_SMP | \mm_mmuflags)
         ALT_UP(.long    PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AP_READ | \
@@ -375,7 +401,7 @@ __v7_setup_stack:
         .long   HWCAP_SWP | HWCAP_HALF | HWCAP_THUMB | HWCAP_FAST_MULT | \
                 HWCAP_EDSP | HWCAP_TLS | \hwcaps
         .long   cpu_v7_name
-        .long   v7_processor_functions
+        .long   \proc_fns
         .long   v7wbi_tlb_fns
         .long   v6_user_fns
         .long   v7_cache_fns
@@ -407,12 +433,14 @@ __v7_ca9mp_proc_info:
         /*
          * Marvell PJ4B processor.
          */
+#ifdef CONFIG_CPU_PJ4B
         .type   __v7_pj4b_proc_info, #object
 __v7_pj4b_proc_info:
         .long   0x560f5800
         .long   0xff0fff00
-        __v7_proc __v7_pj4b_setup
+        __v7_proc __v7_pj4b_setup, proc_fns = pj4b_processor_functions
         .size   __v7_pj4b_proc_info, . - __v7_pj4b_proc_info
+#endif
 
         /*
          * ARM Ltd. Cortex A7 processor.