ARCv2: support manual regfile save on interrupts

There's a hardware bug which affects the HSDK platform, triggered by
micro-ops for auto-saving regfile on taken interrupt. The workaround is
to inhibit autosave.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

5 files changed, 68 insertions, 1 deletions

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 376366a7db81..7215f52b3413 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -407,6 +407,14 @@ config ARC_HAS_ACCL_REGS
           (also referred to as r58:r59). These can also be used by gcc as GPR so
           kernel needs to save/restore per process
 
+config ARC_IRQ_NO_AUTOSAVE
+        bool "Disable hardware autosave regfile on interrupts"
+        default n
+        help
+          On HS cores, taken interrupt auto saves the regfile on stack.
+          This is programmable and can be optionally disabled in which case
+          software INTERRUPT_PROLOGUE/EPILGUE do the needed work
+
 endif   # ISA_ARCV2
 
 endmenu   # "ARC CPU Configuration"
diff --git a/arch/arc/include/asm/entry-arcv2.h b/arch/arc/include/asm/entry-arcv2.h
index 309f4e6721b3..225e7df2d8ed 100644
--- a/arch/arc/include/asm/entry-arcv2.h
+++ b/arch/arc/include/asm/entry-arcv2.h
@@ -17,6 +17,33 @@
         ;
         ; Now manually save: r12, sp, fp, gp, r25
 
+#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE
+.ifnc \called_from, exception
+        st.as   r9, [sp, -10]   ; save r9 in it's final stack slot
+        sub     sp, sp, 12      ; skip JLI, LDI, EI
+
+        PUSH    lp_count
+        PUSHAX  lp_start
+        PUSHAX  lp_end
+        PUSH    blink
+
+        PUSH    r11
+        PUSH    r10
+
+        sub     sp, sp, 4       ; skip r9
+
+        PUSH    r8
+        PUSH    r7
+        PUSH    r6
+        PUSH    r5
+        PUSH    r4
+        PUSH    r3
+        PUSH    r2
+        PUSH    r1
+        PUSH    r0
+.endif
+#endif
+
 #ifdef CONFIG_ARC_HAS_ACCL_REGS
         PUSH    r59
         PUSH    r58
@@ -86,6 +113,33 @@
         POP     r59
 #endif
 
+#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE
+.ifnc \called_from, exception
+        POP     r0
+        POP     r1
+        POP     r2
+        POP     r3
+        POP     r4
+        POP     r5
+        POP     r6
+        POP     r7
+        POP     r8
+        POP     r9
+        POP     r10
+        POP     r11
+
+        POP     blink
+        POPAX   lp_end
+        POPAX   lp_start
+
+        POP     r9
+        mov     lp_count, r9
+
+        add     sp, sp, 12      ; skip JLI, LDI, EI
+        ld.as   r9, [sp, -10]   ; reload r9 which got clobbered
+.endif
+#endif
+
 .endm
 
 /*------------------------------------------------------------------------*/
diff --git a/arch/arc/kernel/entry-arcv2.S b/arch/arc/kernel/entry-arcv2.S
index cc558a25b8fa..562089d62d9d 100644
--- a/arch/arc/kernel/entry-arcv2.S
+++ b/arch/arc/kernel/entry-arcv2.S
@@ -209,7 +209,9 @@ restore_regs:
 ;####### Return from Intr #######
 
 debug_marker_l1:
-        bbit1.nt r0, STATUS_DE_BIT, .Lintr_ret_to_delay_slot
+        ; bbit1.nt r0, STATUS_DE_BIT, .Lintr_ret_to_delay_slot
+        btst    r0, STATUS_DE_BIT               ; Z flag set if bit clear
+        bnz     .Lintr_ret_to_delay_slot        ; branch if STATUS_DE_BIT set
 
 .Lisr_ret_fast_path:
         ; Handle special case #1: (Entry via Exception, Return via IRQ)
diff --git a/arch/arc/kernel/intc-arcv2.c b/arch/arc/kernel/intc-arcv2.c
index 067ea362fb3e..cf18b3e5a934 100644
--- a/arch/arc/kernel/intc-arcv2.c
+++ b/arch/arc/kernel/intc-arcv2.c
@@ -49,11 +49,13 @@ void arc_init_IRQ(void)
 
         *(unsigned int *)&ictrl = 0;
 
+#ifndef CONFIG_ARC_IRQ_NO_AUTOSAVE
         ictrl.save_nr_gpr_pairs = 6;    /* r0 to r11 (r12 saved manually) */
         ictrl.save_blink = 1;
         ictrl.save_lp_regs = 1;         /* LP_COUNT, LP_START, LP_END */
         ictrl.save_u_to_u = 0;          /* user ctxt saved on kernel stack */
         ictrl.save_idx_regs = 1;        /* JLI, LDI, EI */
+#endif
 
         WRITE_AUX(AUX_IRQ_CTRL, ictrl);
 
diff --git a/arch/arc/plat-hsdk/Kconfig b/arch/arc/plat-hsdk/Kconfig
index f25c085b9874..23e00216e5a5 100644
--- a/arch/arc/plat-hsdk/Kconfig
+++ b/arch/arc/plat-hsdk/Kconfig
@@ -9,6 +9,7 @@ menuconfig ARC_SOC_HSDK
         bool "ARC HS Development Kit SOC"
         depends on ISA_ARCV2
         select ARC_HAS_ACCL_REGS
+        select ARC_IRQ_NO_AUTOSAVE
         select CLK_HSDK
         select RESET_HSDK
         select HAVE_PCI