ARM: 7680/1: Detect support for SDIV/UDIV from ISAR0 register

The ISAR0 register indicates support for the SDIV and UDIV
instructions in both the Thumb and ARM instruction set. Read the
register to detect the supported instructions and update the
elf_hwcap mask as appropriate. This is better than adding more
and more cpuid checks in proc-v7.S for each new cpu variant that
supports these instructions.

Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Stepan Moskovchenko <stepanm@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 22 insertions, 2 deletions

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index e2c8bbffb0b1..f3ac13f69b7a 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -353,6 +353,23 @@ void __init early_print(const char *str, ...)
         printk("%s", buf);
 }
 
+static void __init cpuid_init_hwcaps(void)
+{
+        unsigned int divide_instrs;
+
+        if (cpu_architecture() < CPU_ARCH_ARMv7)
+                return;
+
+        divide_instrs = (read_cpuid_ext(CPUID_EXT_ISAR0) & 0x0f000000) >> 24;
+
+        switch (divide_instrs) {
+        case 2:
+                elf_hwcap |= HWCAP_IDIVA;
+        case 1:
+                elf_hwcap |= HWCAP_IDIVT;
+        }
+}
+
 static void __init feat_v6_fixup(void)
 {
         int id = read_cpuid_id();
@@ -483,6 +500,9 @@ static void __init setup_processor(void)
         snprintf(elf_platform, ELF_PLATFORM_SIZE, "%s%c",
                  list->elf_name, ENDIANNESS);
         elf_hwcap = list->elf_hwcap;
+
+        cpuid_init_hwcaps();
+
 #ifndef CONFIG_ARM_THUMB
         elf_hwcap &= ~(HWCAP_THUMB | HWCAP_IDIVT);
 #endif
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 3a3c015f8d5c..bcd3d48922fb 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -420,7 +420,7 @@ __v7_pj4b_proc_info:
 __v7_ca7mp_proc_info:
         .long   0x410fc070
         .long   0xff0ffff0
-        __v7_proc __v7_ca7mp_setup, hwcaps = HWCAP_IDIV
+        __v7_proc __v7_ca7mp_setup
         .size   __v7_ca7mp_proc_info, . - __v7_ca7mp_proc_info
 
         /*
@@ -430,7 +430,7 @@ __v7_ca7mp_proc_info:
 __v7_ca15mp_proc_info:
         .long   0x410fc0f0
         .long   0xff0ffff0
-        __v7_proc __v7_ca15mp_setup, hwcaps = HWCAP_IDIV
+        __v7_proc __v7_ca15mp_setup
         .size   __v7_ca15mp_proc_info, . - __v7_ca15mp_proc_info
 
         /*