ARM: 6207/1: Replace CONFIG_HAS_TLS_REG with HWCAP_TLS and check for it on V6

The TLS register is only available on ARM1136 r1p0 and later.
Set HWCAP_TLS flags if hardware TLS is available and test for
it if CONFIG_CPU_32v6K is not set for V6.

Note that we set the TLS instruction in __kuser_get_tls
dynamically as suggested by Jamie Lokier <jamie@shareable.org>.

Also the __switch_to code is optimized out in most cases as
suggested by Nicolas Pitre <nico@fluxnic.net>.

Reviewed-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 17 insertions, 0 deletions

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 7ae65dc594a4..648c3c1e16c4 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -269,6 +269,21 @@ static void __init cacheid_init(void)
 extern struct proc_info_list *lookup_processor_type(unsigned int);
 extern struct machine_desc *lookup_machine_type(unsigned int);
 
+static void __init feat_v6_fixup(void)
+{
+        int id = read_cpuid_id();
+
+        if ((id & 0xff0f0000) != 0x41070000)
+                return;
+
+        /*
+         * HWCAP_TLS is available only on 1136 r1p0 and later,
+         * see also kuser_get_tls_init.
+         */
+        if ((((id >> 4) & 0xfff) == 0xb36) && (((id >> 20) & 3) == 0))
+                elf_hwcap &= ~HWCAP_TLS;
+}
+
 static void __init setup_processor(void)
 {
         struct proc_info_list *list;
@@ -311,6 +326,8 @@ static void __init setup_processor(void)
         elf_hwcap &= ~HWCAP_THUMB;
 #endif
 
+        feat_v6_fixup();
+
         cacheid_init();
         cpu_proc_init();
 }