sh: rework SuperH Mobile sleep code exception handling

This patch updates the exception handling in the sleep code
for SuperH Mobile. With the patch applied the sleep code
always rewrites the VBR and resumes from the exception vector,
re-initializes hardware and jumps straight to the original
interrupt vector.

Tested on sh7722 and sh7724 with "Sleep Mode", "Sleep Mode + SF"
and "Software Standby Mode + SF" with CONFIG_SUSPEND.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

2 files changed, 107 insertions, 64 deletions

diff --git a/arch/sh/kernel/cpu/shmobile/pm.c b/arch/sh/kernel/cpu/shmobile/pm.c
index de078d24ce5..ee3c2aaf66f 100644
--- a/arch/sh/kernel/cpu/shmobile/pm.c
+++ b/arch/sh/kernel/cpu/shmobile/pm.c
@@ -41,23 +41,11 @@ extern const unsigned int sh_mobile_standby_size;
 
 void sh_mobile_call_standby(unsigned long mode)
 {
-        extern void *vbr_base;
         void *onchip_mem = (void *)ILRAM_BASE;
-        void (*standby_onchip_mem)(unsigned long) = onchip_mem;
-
-        /* Note: Wake up from sleep may generate exceptions!
-         * Setup VBR to point to on-chip ram if self-refresh is
-         * going to be used.
-         */
-        if (mode & SUSP_SH_SF)
-                asm volatile("ldc %0, vbr" : : "r" (onchip_mem) : "memory");
+        void (*standby_onchip_mem)(unsigned long, unsigned long) = onchip_mem;
 
         /* Let assembly snippet in on-chip memory handle the rest */
-        standby_onchip_mem(mode);
-
-        /* Put VBR back in System RAM again */
-        if (mode & SUSP_SH_SF)
-                asm volatile("ldc %0, vbr" : : "r" (&vbr_base) : "memory");
+        standby_onchip_mem(mode, ILRAM_BASE);
 }
 
 static int sh_pm_enter(suspend_state_t state)
diff --git a/arch/sh/kernel/cpu/shmobile/sleep.S b/arch/sh/kernel/cpu/shmobile/sleep.S
index baf2d7d46b0..a439e6c7824 100644
--- a/arch/sh/kernel/cpu/shmobile/sleep.S
+++ b/arch/sh/kernel/cpu/shmobile/sleep.S
@@ -16,19 +16,52 @@
 #include <asm/asm-offsets.h>
 #include <asm/suspend.h>
 
+/*
+ * Kernel mode register usage, see entry.S:
+ *      k0      scratch
+ *      k1      scratch
+ *      k4      scratch
+ */
+#define k0      r0
+#define k1      r1
+#define k4      r4
+
 /* manage self-refresh and enter standby mode.
  * this code will be copied to on-chip memory and executed from there.
  */
 
         .balign         4096,0,4096
 ENTRY(sh_mobile_standby)
+
+        /* save original vbr */
+        stc     vbr, r1
+        mova    saved_vbr, r0
+        mov.l   r1, @r0
+
+        /* point vbr to our on-chip memory page */
+        ldc     r5, vbr
+
+        /* save return address */
+        mova    saved_spc, r0
+        sts     pr, r5
+        mov.l   r5, @r0
+
+        /* save sr */
+        mova    saved_sr, r0
+        stc     sr, r5
+        mov.l   r5, @r0
+
+        /* save mode flags */
+        mova    saved_mode, r0
+        mov.l   r4, @r0
+
+        /* put mode flags in r0 */
         mov     r4, r0
 
         tst     #SUSP_SH_SF, r0
         bt      skip_set_sf
 #ifdef CONFIG_CPU_SUBTYPE_SH7724
         /* DBSC: put memory in self-refresh mode */
-
         mov.l   dben_reg, r4
         mov.l   dben_data0, r1
         mov.l   r1, @r4
@@ -60,14 +93,6 @@ ENTRY(sh_mobile_standby)
 #endif
 
 skip_set_sf:
-        tst     #SUSP_SH_SLEEP, r0
-        bt      test_standby
-
-        /* set mode to "sleep mode" */
-        bra     do_sleep
-         mov    #0x00, r1
-
-test_standby:
         tst     #SUSP_SH_STANDBY, r0
         bt      test_rstandby
 
@@ -85,77 +110,107 @@ test_rstandby:
 
 test_ustandby:
         tst     #SUSP_SH_USTANDBY, r0
-        bt      done_sleep
+        bt      force_sleep
 
         /* set mode to "u-standby mode" */
-        mov     #0x10, r1
+        bra     do_sleep
+         mov    #0x10, r1
 
-        /* fall-through */
+force_sleep:
+
+        /* set mode to "sleep mode" */
+        mov     #0x00, r1
 
 do_sleep:
         /* setup and enter selected standby mode */
         mov.l   5f, r4
         mov.l   r1, @r4
+again:
         sleep
+        bra     again
+         nop
+
+restore_jump_vbr:
+        /* setup spc with return address to c code */
+        mov.l   saved_spc, k0
+        ldc     k0, spc
+
+        /* restore vbr */
+        mov.l   saved_vbr, k0
+        ldc     k0, vbr
+
+        /* setup ssr with saved sr */
+        mov.l   saved_sr, k0
+        ldc     k0, ssr
+
+        /* get mode flags */
+        mov.l   saved_mode, k0
 
 done_sleep:
         /* reset standby mode to sleep mode */
-        mov.l   5f, r4
-        mov     #0x00, r1
-        mov.l   r1, @r4
+        mov.l   5f, k4
+        mov     #0x00, k1
+        mov.l   k1, @k4
 
-        tst     #SUSP_SH_SF, r0
+        tst     #SUSP_SH_SF, k0
         bt      skip_restore_sf
 
 #ifdef CONFIG_CPU_SUBTYPE_SH7724
         /* DBSC: put memory in auto-refresh mode */
+        mov.l   dbrfpdn0_reg, k4
+        mov.l   dbrfpdn0_data0, k1
+        mov.l   k1, @k4
 
-        mov.l   dbrfpdn0_reg, r4
-        mov.l   dbrfpdn0_data0, r1
-        mov.l   r1, @r4
-
-        /* sleep 140 ns */
-        nop
+        nop /* sleep 140 ns */
         nop
         nop
         nop
 
-        mov.l   dbcmdcnt_reg, r4
-        mov.l   dbcmdcnt_data0, r1
-        mov.l   r1, @r4
+        mov.l   dbcmdcnt_reg, k4
+        mov.l   dbcmdcnt_data0, k1
+        mov.l   k1, @k4
 
-        mov.l   dbcmdcnt_reg, r4
-        mov.l   dbcmdcnt_data1, r1
-        mov.l   r1, @r4
+        mov.l   dbcmdcnt_reg, k4
+        mov.l   dbcmdcnt_data1, k1
+        mov.l   k1, @k4
 
-        mov.l   dben_reg, r4
-        mov.l   dben_data1, r1
-        mov.l   r1, @r4
+        mov.l   dben_reg, k4
+        mov.l   dben_data1, k1
+        mov.l   k1, @k4
 
-        mov.l   dbrfpdn0_reg, r4
-        mov.l   dbrfpdn0_data2, r1
-        mov.l   r1, @r4
+        mov.l   dbrfpdn0_reg, k4
+        mov.l   dbrfpdn0_data2, k1
+        mov.l   k1, @k4
 #else
         /* SBSC: set auto-refresh mode */
-        mov.l   1f, r4
-        mov.l   @r4, r2
-        mov.l   4f, r3
-        and     r3, r2
-        mov.l   r2, @r4
-        mov.l   6f, r4
-        mov.l   7f, r1
-        mov.l   8f, r2
-        mov.l   @r4, r3
-        mov     #-1, r4
-        add     r4, r3
-        or      r2, r3
-        mov.l   r3, @r1
+        mov.l   1f, k4
+        mov.l   @k4, k0
+        mov.l   4f, k1
+        and     k1, k0
+        mov.l   k0, @k4
+        mov.l   6f, k4
+        mov.l   8f, k0
+        mov.l   @k4, k1
+        mov     #-1, k4
+        add     k4, k1
+        or      k1, k0
+        mov.l   7f, k1
+        mov.l   k0, @k1
 #endif
 skip_restore_sf:
-        rts
+        /* jump to vbr vector */
+        mov.l   saved_vbr, k0
+        mov.l   offset_vbr, k4
+        add     k4, k0
+        jmp     @k0
          nop
 
         .balign 4
+saved_mode:     .long   0
+saved_spc:      .long   0
+saved_sr:       .long   0
+saved_vbr:      .long   0
+offset_vbr:     .long   0x600
 #ifdef CONFIG_CPU_SUBTYPE_SH7724
 dben_reg:       .long   0xfd000010 /* DBEN */
 dben_data0:     .long   0
@@ -178,12 +233,12 @@ dbcmdcnt_data1:	.long	4
 7:      .long   0xfe400018 /* RTCNT */
 8:      .long   0xa55a0000
 
+
 /* interrupt vector @ 0x600 */
         .balign         0x400,0,0x400
         .long   0xdeadbeef
         .balign         0x200,0,0x200
-        /* sh7722 will end up here in sleep mode */
-        rte
+        bra     restore_jump_vbr
          nop
 sh_mobile_standby_end: