[S390] rework idle code

Whenever the cpu loads an enabled wait PSW it will appear as idle to the
underlying host system. The code in default_idle calls vtime_stop_cpu
which does the necessary voodoo to get the cpu time accounting right.
The udelay code just loads an enabled wait PSW. To correct this rework
the vtime_stop_cpu/vtime_start_cpu logic and move the difficult parts
to entry[64].S, vtime_stop_cpu can now be called from anywhere and
vtime_start_cpu is gone. The correction of the cpu time during wakeup
from an enabled wait PSW is done with a critical section in entry[64].S.
As vtime_start_cpu is gone, s390_idle_check can be removed as well.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 70 insertions, 6 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 6143521a4fff..74ee563fe62b 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -105,14 +105,14 @@ STACK_SIZE  = 1 << STACK_SHIFT
 
         .macro  ADD64 high,low,timer
         al      \high,\timer
-        al      \low,\timer+4
+        al      \low,4+\timer
         brc     12,.+8
         ahi     \high,1
         .endm
 
         .macro  SUB64 high,low,timer
         sl      \high,\timer
-        sl      \low,\timer+4
+        sl      \low,4+\timer
         brc     3,.+8
         ahi     \high,-1
         .endm
@@ -471,7 +471,6 @@ io_tif:
         jnz     io_work                 # there is work to do (signals etc.)
 io_restore:
         mvc     __LC_RETURN_PSW(8),__PT_PSW(%r11)
-        ni      __LC_RETURN_PSW+1,0xfd  # clean wait state bit
         stpt    __LC_EXIT_TIMER
         lm      %r0,%r15,__PT_R0(%r11)
         lpsw    __LC_RETURN_PSW
@@ -612,6 +611,26 @@ ext_skip:
         basr    %r14,%r1                # call do_extint
         j       io_return
 
+/*
+ * Load idle PSW. The second "half" of this function is in cleanup_idle.
+ */
+ENTRY(psw_idle)
+        st      %r4,__SF_EMPTY(%r15)
+        basr    %r1,0
+        la      %r1,psw_idle_lpsw+4-.(%r1)
+        st      %r1,__SF_EMPTY+4(%r15)
+        oi      __SF_EMPTY+4(%r15),0x80
+        la      %r1,.Lvtimer_max-psw_idle_lpsw-4(%r1)
+        stck    __IDLE_ENTER(%r2)
+        ltr     %r5,%r5
+        stpt    __VQ_IDLE_ENTER(%r3)
+        jz      psw_idle_lpsw
+        spt     0(%r1)
+psw_idle_lpsw:
+        lpsw    __SF_EMPTY(%r15)
+        br      %r14
+psw_idle_end:
+
 __critical_end:
 
 /*
@@ -673,7 +692,6 @@ mcck_skip:
         TRACE_IRQS_ON
 mcck_return:
         mvc     __LC_RETURN_MCCK_PSW(8),__PT_PSW(%r11) # move return PSW
-        ni      __LC_RETURN_MCCK_PSW+1,0xfd # clear wait state bit
         tm      __LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?
         jno     0f
         lm      %r0,%r15,__PT_R0(%r11)
@@ -748,6 +766,8 @@ cleanup_table:
         .long   io_tif + 0x80000000
         .long   io_restore + 0x80000000
         .long   io_done + 0x80000000
+        .long   psw_idle + 0x80000000
+        .long   psw_idle_end + 0x80000000
 
 cleanup_critical:
         cl      %r9,BASED(cleanup_table)        # system_call
@@ -766,6 +786,10 @@ cleanup_critical:
         jl      cleanup_io_tif
         cl      %r9,BASED(cleanup_table+28)     # io_done
         jl      cleanup_io_restore
+        cl      %r9,BASED(cleanup_table+32)     # psw_idle
+        jl      0f
+        cl      %r9,BASED(cleanup_table+36)     # psw_idle_end
+        jl      cleanup_idle
 0:      br      %r14
 
 cleanup_system_call:
@@ -849,7 +873,6 @@ cleanup_io_restore:
         jhe     0f
         l       %r9,12(%r11)            # get saved r11 pointer to pt_regs
         mvc     __LC_RETURN_PSW(8),__PT_PSW(%r9)
-        ni      __LC_RETURN_PSW+1,0xfd  # clear wait state bit
         mvc     0(32,%r11),__PT_R8(%r9)
         lm      %r0,%r7,__PT_R0(%r9)
 0:      lm      %r8,%r9,__LC_RETURN_PSW
@@ -857,11 +880,52 @@ cleanup_io_restore:
 cleanup_io_restore_insn:
         .long   io_done - 4 + 0x80000000
 
+cleanup_idle:
+        # copy interrupt clock & cpu timer
+        mvc     __IDLE_EXIT(8,%r2),__LC_INT_CLOCK
+        mvc     __VQ_IDLE_EXIT(8,%r3),__LC_ASYNC_ENTER_TIMER
+        chi     %r11,__LC_SAVE_AREA_ASYNC
+        je      0f
+        mvc     __IDLE_EXIT(8,%r2),__LC_MCCK_CLOCK
+        mvc     __VQ_IDLE_EXIT(8,%r3),__LC_MCCK_ENTER_TIMER
+0:      # check if stck has been executed
+        cl      %r9,BASED(cleanup_idle_insn)
+        jhe     1f
+        mvc     __IDLE_ENTER(8,%r2),__IDLE_EXIT(%r2)
+        mvc     __VQ_IDLE_ENTER(8,%r3),__VQ_IDLE_EXIT(%r3)
+        j       2f
+1:      # check if the cpu timer has been reprogrammed
+        ltr     %r5,%r5
+        jz      2f
+        spt     __VQ_IDLE_ENTER(%r3)
+2:      # account system time going idle
+        lm      %r9,%r10,__LC_STEAL_TIMER
+        ADD64   %r9,%r10,__IDLE_ENTER(%r2)
+        SUB64   %r9,%r10,__LC_LAST_UPDATE_CLOCK
+        stm     %r9,%r10,__LC_STEAL_TIMER
+        mvc     __LC_LAST_UPDATE_CLOCK(8),__IDLE_EXIT(%r2)
+        lm      %r9,%r10,__LC_SYSTEM_TIMER
+        ADD64   %r9,%r10,__LC_LAST_UPDATE_TIMER
+        SUB64   %r9,%r10,__VQ_IDLE_ENTER(%r3)
+        stm     %r9,%r10,__LC_SYSTEM_TIMER
+        mvc     __LC_LAST_UPDATE_TIMER(8),__VQ_IDLE_EXIT(%r3)
+        # prepare return psw
+        n       %r8,BASED(cleanup_idle_wait)    # clear wait state bit
+        l       %r9,24(%r11)                    # return from psw_idle
+        br      %r14
+cleanup_idle_insn:
+        .long   psw_idle_lpsw + 0x80000000
+cleanup_idle_wait:
+        .long   0xfffdffff
+
 /*
  * Integer constants
  */
         .align  4
-.Lnr_syscalls:          .long   NR_syscalls
+.Lnr_syscalls:
+        .long   NR_syscalls
+.Lvtimer_max:
+        .quad   0x7fffffffffffffff
 
 /*
  * Symbol constants