microblaze: Add support from PREEMPT

This patch add core PREEMPT support for Microblaze.
I tried to trace it via tracers and I was able to see any output.

I also added low level debug functions to see if that code is called.

Signed-off-by: Michal Simek <monstr@monstr.eu>

2 files changed, 25 insertions, 1 deletions

diff --git a/arch/microblaze/kernel/asm-offsets.c b/arch/microblaze/kernel/asm-offsets.c
index 7bc7b68f97db..0071260a672c 100644
--- a/arch/microblaze/kernel/asm-offsets.c
+++ b/arch/microblaze/kernel/asm-offsets.c
@@ -90,6 +90,7 @@ int main(int argc, char *argv[])
         DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
         DEFINE(TI_ADDR_LIMIT, offsetof(struct thread_info, addr_limit));
         DEFINE(TI_CPU_CONTEXT, offsetof(struct thread_info, cpu_context));
+        DEFINE(TI_PREEMPT_COUNT, offsetof(struct thread_info, preempt_count));
         BLANK();
 
         /* struct cpu_context */
diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index 3bad4ff49471..1a6729dde49e 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/arch/microblaze/kernel/entry.S
@@ -853,7 +853,30 @@ no_intr_resched:
         lwi     r1, r1, PT_R1 - PT_SIZE;
         bri     6f;
 /* MS: Return to kernel state. */
-2:      VM_OFF /* MS: turn off MMU */
+2:
+#ifdef CONFIG_PREEMPT
+        add     r11, r0, CURRENT_TASK;
+        lwi     r11, r11, TS_THREAD_INFO;
+        /* MS: get preempt_count from thread info */
+        lwi     r5, r11, TI_PREEMPT_COUNT;
+        bgti    r5, restore;
+
+        lwi     r5, r11, TI_FLAGS;              /* get flags in thread info */
+        andi    r5, r5, _TIF_NEED_RESCHED;
+        beqi    r5, restore /* if zero jump over */
+
+preempt:
+        /* interrupts are off that's why I am calling preempt_chedule_irq */
+        bralid  r15, preempt_schedule_irq
+        nop
+        add     r11, r0, CURRENT_TASK;  /* Get current task ptr into r11 */
+        lwi     r11, r11, TS_THREAD_INFO;       /* get thread info */
+        lwi     r5, r11, TI_FLAGS;              /* get flags in thread info */
+        andi    r5, r5, _TIF_NEED_RESCHED;
+        bnei    r5, preempt /* if non zero jump to resched */
+restore:
+#endif
+        VM_OFF /* MS: turn off MMU */
         tophys(r1,r1)
         lwi     r3, r1, PTO + PT_R3; /* MS: restore saved r3, r4 registers */
         lwi     r4, r1, PTO + PT_R4;