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>

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 376366a..7215f52 100644 (file)
--- 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 309f4e6..225e7df 100644 (file)
--- 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 cc558a2..562089d 100644 (file)
--- 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 067ea36..cf18b3e 100644 (file)
--- 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 f25c085..23e0021 100644 (file)
--- 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