summaryrefslogtreecommitdiffstats
path: root/arch/arm/vfp/vfphw.S
diff options
context:
space:
mode:
Diffstat (limited to 'arch/arm/vfp/vfphw.S')
-rw-r--r--arch/arm/vfp/vfphw.S63
1 files changed, 43 insertions, 20 deletions
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index 9897dcf..2d30c7f 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -77,27 +77,27 @@ ENTRY(vfp_support_entry)
bne look_for_VFP_exceptions @ VFP is already enabled
DBGSTR1 "enable %x", r10
- ldr r3, last_VFP_context_address
+ ldr r3, vfp_current_hw_state_address
orr r1, r1, #FPEXC_EN @ user FPEXC has the enable bit set
- ldr r4, [r3, r11, lsl #2] @ last_VFP_context pointer
+ ldr r4, [r3, r11, lsl #2] @ vfp_current_hw_state pointer
bic r5, r1, #FPEXC_EX @ make sure exceptions are disabled
- cmp r4, r10
- beq check_for_exception @ we are returning to the same
- @ process, so the registers are
- @ still there. In this case, we do
- @ not want to drop a pending exception.
+ cmp r4, r10 @ this thread owns the hw context?
+#ifndef CONFIG_SMP
+ @ For UP, checking that this thread owns the hw context is
+ @ sufficient to determine that the hardware state is valid.
+ beq vfp_hw_state_valid
+
+ @ On UP, we lazily save the VFP context. As a different
+ @ thread wants ownership of the VFP hardware, save the old
+ @ state if there was a previous (valid) owner.
VFPFMXR FPEXC, r5 @ enable VFP, disable any pending
@ exceptions, so we can get at the
@ rest of it
-#ifndef CONFIG_SMP
- @ Save out the current registers to the old thread state
- @ No need for SMP since this is not done lazily
-
DBGSTR1 "save old state %p", r4
- cmp r4, #0
- beq no_old_VFP_process
+ cmp r4, #0 @ if the vfp_current_hw_state is NULL
+ beq vfp_reload_hw @ then the hw state needs reloading
VFPFSTMIA r4, r5 @ save the working registers
VFPFMRX r5, FPSCR @ current status
#ifndef CONFIG_CPU_FEROCEON
@@ -110,13 +110,35 @@ ENTRY(vfp_support_entry)
1:
#endif
stmia r4, {r1, r5, r6, r8} @ save FPEXC, FPSCR, FPINST, FPINST2
- @ and point r4 at the word at the
- @ start of the register dump
+vfp_reload_hw:
+
+#else
+ @ For SMP, if this thread does not own the hw context, then we
+ @ need to reload it. No need to save the old state as on SMP,
+ @ we always save the state when we switch away from a thread.
+ bne vfp_reload_hw
+
+ @ This thread has ownership of the current hardware context.
+ @ However, it may have been migrated to another CPU, in which
+ @ case the saved state is newer than the hardware context.
+ @ Check this by looking at the CPU number which the state was
+ @ last loaded onto.
+ ldr ip, [r10, #VFP_CPU]
+ teq ip, r11
+ beq vfp_hw_state_valid
+
+vfp_reload_hw:
+ @ We're loading this threads state into the VFP hardware. Update
+ @ the CPU number which contains the most up to date VFP context.
+ str r11, [r10, #VFP_CPU]
+
+ VFPFMXR FPEXC, r5 @ enable VFP, disable any pending
+ @ exceptions, so we can get at the
+ @ rest of it
#endif
-no_old_VFP_process:
DBGSTR1 "load state %p", r10
- str r10, [r3, r11, lsl #2] @ update the last_VFP_context pointer
+ str r10, [r3, r11, lsl #2] @ update the vfp_current_hw_state pointer
@ Load the saved state back into the VFP
VFPFLDMIA r10, r5 @ reload the working registers while
@ FPEXC is in a safe state
@@ -132,7 +154,8 @@ no_old_VFP_process:
#endif
VFPFMXR FPSCR, r5 @ restore status
-check_for_exception:
+@ The context stored in the VFP hardware is up to date with this thread
+vfp_hw_state_valid:
tst r1, #FPEXC_EX
bne process_exception @ might as well handle the pending
@ exception before retrying branch
@@ -207,8 +230,8 @@ ENTRY(vfp_save_state)
ENDPROC(vfp_save_state)
.align
-last_VFP_context_address:
- .word last_VFP_context
+vfp_current_hw_state_address:
+ .word vfp_current_hw_state
.macro tbl_branch, base, tmp, shift
#ifdef CONFIG_THUMB2_KERNEL
OpenPOWER on IntegriCloud