powerpc/vdso32: Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE

This is copied and adapted from commit 5c929885f1bb ("powerpc/vdso64:
Add support for CLOCK_{REALTIME/MONOTONIC}_COARSE")
from Santosh Sivaraj <santosh@fossix.org>

Benchmark from vdsotest-all:
clock-gettime-realtime: syscall: 3601 nsec/call
clock-gettime-realtime:    libc: 1072 nsec/call
clock-gettime-realtime:    vdso: 931 nsec/call
clock-gettime-monotonic: syscall: 4034 nsec/call
clock-gettime-monotonic:    libc: 1213 nsec/call
clock-gettime-monotonic:    vdso: 1076 nsec/call
clock-gettime-realtime-coarse: syscall: 2722 nsec/call
clock-gettime-realtime-coarse:    libc: 805 nsec/call
clock-gettime-realtime-coarse:    vdso: 668 nsec/call
clock-gettime-monotonic-coarse: syscall: 2949 nsec/call
clock-gettime-monotonic-coarse:    libc: 882 nsec/call
clock-gettime-monotonic-coarse:    vdso: 745 nsec/call

Additional test passed with:
	vdsotest -d 30 clock-gettime-monotonic-coarse verify

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://github.com/linuxppc/issues/issues/41
Link: https://lore.kernel.org/r/d1d24a376e396540194eeb85a2efe481e92ade24.1575273217.git.christophe.leroy@c-s.fr

diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
index 3306672..e9ce8ee 100644 (file)
--- a/arch/powerpc/kernel/vdso32/gettimeofday.S
+++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
@@ -69,7 +69,13 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
        cmpli   cr0,r3,CLOCK_REALTIME
        cmpli   cr1,r3,CLOCK_MONOTONIC
        cror    cr0*4+eq,cr0*4+eq,cr1*4+eq
-       bne     cr0,99f
+
+       cmpli   cr5,r3,CLOCK_REALTIME_COARSE
+       cmpli   cr6,r3,CLOCK_MONOTONIC_COARSE
+       cror    cr5*4+eq,cr5*4+eq,cr6*4+eq
+
+       cror    cr0*4+eq,cr0*4+eq,cr5*4+eq
+       bne     cr0, .Lgettime_fallback
 
        mflr    r12                     /* r12 saves lr */
   .cfi_register lr,r12
@@ -78,8 +84,10 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
        mr      r9,r3                   /* datapage ptr in r9 */
        lis     r7,NSEC_PER_SEC@h       /* want nanoseconds */
        ori     r7,r7,NSEC_PER_SEC@l
-50:    bl      __do_get_tspec@local    /* get sec/nsec from tb & kernel */
-       bne     cr1,80f                 /* not monotonic -> all done */
+       beq     cr5, .Lcoarse_clocks
+.Lprecise_clocks:
+       bl      __do_get_tspec@local    /* get sec/nsec from tb & kernel */
+       bne     cr1, .Lfinish           /* not monotonic -> all done */
 
        /*
         * CLOCK_MONOTONIC
@@ -103,12 +111,53 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
        add     r9,r9,r0
        lwz     r0,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
         cmpl    cr0,r8,r0              /* check if updated */
-       bne-    50b
+       bne-    .Lprecise_clocks
+       b       .Lfinish_monotonic
+
+       /*
+        * For coarse clocks we get data directly from the vdso data page, so
+        * we don't need to call __do_get_tspec, but we still need to do the
+        * counter trick.
+        */
+.Lcoarse_clocks:
+       lwz     r8,(CFG_TB_UPDATE_COUNT+LOPART)(r9)
+       andi.   r0,r8,1                 /* pending update ? loop */
+       bne-    .Lcoarse_clocks
+       add     r9,r9,r0                /* r0 is already 0 */
+
+       /*
+        * CLOCK_REALTIME_COARSE, below values are needed for MONOTONIC_COARSE
+        * too
+        */
+       lwz     r3,STAMP_XTIME_SEC+LOPART(r9)
+       lwz     r4,STAMP_XTIME_NSEC+LOPART(r9)
+       bne     cr6,1f
+
+       /* CLOCK_MONOTONIC_COARSE */
+       lwz     r5,(WTOM_CLOCK_SEC+LOPART)(r9)
+       lwz     r6,WTOM_CLOCK_NSEC(r9)
+
+       /* check if counter has updated */
+       or      r0,r6,r5
+1:     or      r0,r0,r3
+       or      r0,r0,r4
+       xor     r0,r0,r0
+       add     r3,r3,r0
+       lwz     r0,CFG_TB_UPDATE_COUNT+LOPART(r9)
+       cmpl    cr0,r0,r8               /* check if updated */
+       bne-    .Lcoarse_clocks
+
+       /* Counter has not updated, so continue calculating proper values for
+        * sec and nsec if monotonic coarse, or just return with the proper
+        * values for realtime.
+        */
+       bne     cr6, .Lfinish
 
        /* Calculate and store result. Note that this mimics the C code,
         * which may cause funny results if nsec goes negative... is that
         * possible at all ?
         */
+.Lfinish_monotonic:
        add     r3,r3,r5
        add     r4,r4,r6
        cmpw    cr0,r4,r7
@@ -116,11 +165,12 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
        blt     1f
        subf    r4,r7,r4
        addi    r3,r3,1
-1:     bge     cr1,80f
+1:     bge     cr1, .Lfinish
        addi    r3,r3,-1
        add     r4,r4,r7
 
-80:    stw     r3,TSPC32_TV_SEC(r11)
+.Lfinish:
+       stw     r3,TSPC32_TV_SEC(r11)
        stw     r4,TSPC32_TV_NSEC(r11)
 
        mtlr    r12
@@ -131,7 +181,7 @@ V_FUNCTION_BEGIN(__kernel_clock_gettime)
        /*
         * syscall fallback
         */
-99:
+.Lgettime_fallback:
        li      r0,__NR_clock_gettime
   .cfi_restore lr
        sc