* Tony Lindgren <tony@xxxxxxxxxxx> [100318 09:55]:
> * Catalin Marinas <catalin.marinas@xxxxxxx> [100318 04:10]:
> > On Wed, 2010-03-17 at 19:11 +0000, Tony Lindgren wrote:
> > > * Catalin Marinas <catalin.marinas@xxxxxxx> [100317 11:04]:
> > > > On Wed, 2010-03-17 at 17:57 +0000, Tony Lindgren wrote:
> > > > > HAS_TLS reg is only on ARM11 starting with r1p0:
> > > > >
> > > > > http://infocenter.arm.com/help/topic/com.arm.doc.ddi0211k/Babeihid.html
> > > > >
> > > > > So that explains why it won't work on omap2420 as it's r0p2.
> > > >
> > > > Same here, would it work with dynamic detection?
> > >
> > > Hmm I believe here the problem is __switch_to in entry-armv.S.
> > > I don't think we want to dynamically test it every time.. Or
> > > at least it would have to be optimized out in most cases.
> >
> > But if you disable this, you won't be able to use an SMP build on both
> > v6 and v7. Anyway, I don't think that dynamically checking this would
> > introduce performance penalties, the __switch_to code is pretty complex
> > already with all the notifier calls.
>
> OK. I'll take a look at setting the TLS a HWCAP flag.
Below is a patch for convert CONFIG_HAS_TLS_REG into HWCAP_TLS.
I've tested it with V6 r0p2 with no HWCAP_TLS, and V7 that has HWCAP_TLS.
I also forced CONFIG_TLS_REG_EMUL and booted on V6 r0p2, and it booted OK.
Could somebody please test this patch on a real CONFIG_TLS_REG_EMUL
system?
Also, I wonder if the change __kuser_get_tls is safe?
I changed it to assume that if 0xffff0ff0 == 0, then we have HWCAP_TLS.
Regards,
Tony
>From 81d4bf2481c4ef5fd80261605977b5f55e4515e4 Mon Sep 17 00:00:00 2001
From: Tony Lindgren <tony@xxxxxxxxxxx>
Date: Thu, 18 Mar 2010 12:02:43 -0700
Subject: [PATCH] arm: Replace CONFIG_HAS_TLS_REG with HWCAP_TLS and check for it on V6
The TLS register is only available on V6 r1p0 and later.
Test for it and use it if available.
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
diff --git a/arch/arm/include/asm/hwcap.h b/arch/arm/include/asm/hwcap.h
index f7bd52b..c1062c3 100644
--- a/arch/arm/include/asm/hwcap.h
+++ b/arch/arm/include/asm/hwcap.h
@@ -19,6 +19,7 @@
#define HWCAP_NEON 4096
#define HWCAP_VFPv3 8192
#define HWCAP_VFPv3D16 16384
+#define HWCAP_TLS 32768
#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
/*
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 6c5cf36..5a5aac8 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -739,11 +739,13 @@ ENTRY(__switch_to)
#ifdef CONFIG_MMU
ldr r6, [r2, #TI_CPU_DOMAIN]
#endif
-#if defined(CONFIG_HAS_TLS_REG)
- mcr p15, 0, r3, c13, c0, 3 @ set TLS register
-#elif !defined(CONFIG_TLS_REG_EMUL)
- mov r4, #0xffff0fff
- str r3, [r4, #-15] @ TLS val at 0xffff0ff0
+#if !defined(CONFIG_TLS_REG_EMUL)
+ ldr r4, =elf_hwcap
+ ldr r4, [r4, #0]
+ tst r4, #HWCAP_TLS @ hardware with TLS?
+ mcrne p15, 0, r3, c13, c0, 3 @ set TLS register
+ moveq r4, #0xffff0fff
+ streq r3, [r4, #-15] @ TLS val at 0xffff0ff0
#endif
#ifdef CONFIG_MMU
mcr p15, 0, r6, c3, c0, 0 @ Set domain register
@@ -1009,15 +1011,12 @@ kuser_cmpxchg_fixup:
*/
__kuser_get_tls: @ 0xffff0fe0
-
-#if !defined(CONFIG_HAS_TLS_REG) && !defined(CONFIG_TLS_REG_EMUL)
- ldr r0, [pc, #(16 - 8)] @ TLS stored at 0xffff0ff0
-#else
- mrc p15, 0, r0, c13, c0, 3 @ read TLS register
-#endif
+ ldr r0, [pc, #(16 - 8)] @ TLS set at 0xffff0ff0?
+ cmp r0, #0 @ assume hw TLS if not set
+ mrceq p15, 0, r0, c13, c0, 3 @ read TLS register
usr_ret lr
- .rep 5
+ .rep 3
.word 0 @ pad up to __kuser_helper_version
.endr
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index c91c77b..de9d2dc 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -269,6 +269,24 @@ 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);
+#ifdef CONFIG_CPU_V6
+static void __init feat_v6_fixup(void)
+{
+ int id = read_cpuid_id();
+
+ if (id & 0x000f0000 != 0x00070000)
+ return;
+
+ /* HWCAP_TLS is available only on V6 r1p0 and later */
+ if (((id >> 20) & 3) == 0)
+ elf_hwcap &= ~HWCAP_TLS;
+}
+#else
+static inline void feat_v6_fixup(void)
+{
+}
+#endif
+
static void __init setup_processor(void)
{
struct proc_info_list *list;
@@ -311,6 +329,8 @@ static void __init setup_processor(void)
elf_hwcap &= ~HWCAP_THUMB;
#endif
+ feat_v6_fixup();
+
cacheid_init();
cpu_proc_init();
}
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 1621e53..bdffef5 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -518,16 +518,19 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
case NR(set_tls):
thread->tp_value = regs->ARM_r0;
-#if defined(CONFIG_HAS_TLS_REG)
- asm ("mcr p15, 0, %0, c13, c0, 3" : : "r" (regs->ARM_r0) );
-#elif !defined(CONFIG_TLS_REG_EMUL)
- /*
- * User space must never try to access this directly.
- * Expect your app to break eventually if you do so.
- * The user helper at 0xffff0fe0 must be used instead.
- * (see entry-armv.S for details)
- */
- *((unsigned int *)0xffff0ff0) = regs->ARM_r0;
+#if !defined(CONFIG_TLS_REG_EMUL)
+ if (elf_hwcap & HWCAP_TLS) {
+ asm ("mcr p15, 0, %0, c13, c0, 3"
+ : : "r" (regs->ARM_r0));
+ } else {
+ /*
+ * User space must never try to access this directly.
+ * Expect your app to break eventually if you do so.
+ * The user helper at 0xffff0fe0 must be used instead.
+ * (see entry-armv.S for details)
+ */
+ *((unsigned int *)0xffff0ff0) = regs->ARM_r0;
+ }
#endif
return 0;
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index c4ed9f9..45e99c1 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -715,17 +715,6 @@ config TLS_REG_EMUL
a few prototypes like that in existence) and therefore access to
that required register must be emulated.
-config HAS_TLS_REG
- bool
- depends on !TLS_REG_EMUL
- default y if SMP || CPU_32v7
- help
- This selects support for the CP15 thread register.
- It is defined to be available on some ARMv6 processors (including
- all SMP capable ARMv6's) or later processors. User space may
- assume directly accessing that register and always obtain the
- expected value only on ARMv7 and above.
-
config NEEDS_SYSCALL_FOR_CMPXCHG
bool
help
diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S
index 7a5337e..e10626a 100644
--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -239,7 +239,8 @@ __v6_proc_info:
b __v6_setup
.long cpu_arch_name
.long cpu_elf_name
- .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP|HWCAP_JAVA
+ /* See also feat_v6_fixup() for HWCAP_TLS */
+ .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP|HWCAP_JAVA|HWCAP_TLS
.long cpu_v6_name
.long v6_processor_functions
.long v6wbi_tlb_fns
@@ -262,7 +263,8 @@ __pj4_v6_proc_info:
b __v6_setup
.long cpu_arch_name
.long cpu_elf_name
- .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP
+ /* See also feat_v6_fixup() for HWCAP_TLS */
+ .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP|HWCAP_TLS
.long cpu_pj4_name
.long v6_processor_functions
.long v6wbi_tlb_fns
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 7aaf88a..8071bcd 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -344,7 +344,7 @@ __v7_proc_info:
b __v7_setup
.long cpu_arch_name
.long cpu_elf_name
- .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP
+ .long HWCAP_SWP|HWCAP_HALF|HWCAP_THUMB|HWCAP_FAST_MULT|HWCAP_EDSP|HWCAP_TLS
.long cpu_v7_name
.long v7_processor_functions
.long v7wbi_tlb_fns
