arm64: vdso: rework __do_get_tspec register allocation and return shift

In preparation for sub-ns precision in the vdso timespec maths, change
the __do_get_tspec register allocation so that we return the clocksource
shift value instead of the unused xtime tspec.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
index 3a7bdcd..99b7d40 100644 (file)
--- a/arch/arm64/kernel/vdso/gettimeofday.S
+++ b/arch/arm64/kernel/vdso/gettimeofday.S
@@ -62,18 +62,18 @@ ENTRY(__kernel_gettimeofday)
        /* If tv is NULL, skip to the timezone code. */
        cbz     x0, 2f
        bl      __do_get_tspec
-       seqcnt_check w13, 1b
+       seqcnt_check w9, 1b
 
        /* Convert ns to us. */
-       mov     x11, #1000
-       udiv    x10, x10, x11
-       stp     x9, x10, [x0, #TVAL_TV_SEC]
+       mov     x13, #1000
+       udiv    x11, x11, x13
+       stp     x10, x11, [x0, #TVAL_TV_SEC]
 2:
        /* If tz is NULL, return 0. */
        cbz     x1, 3f
        ldp     w4, w5, [vdso_data, #VDSO_TZ_MINWEST]
-       seqcnt_read w13
-       seqcnt_check w13, 1b
+       seqcnt_read w9
+       seqcnt_check w9, 1b
        stp     w4, w5, [x1, #TZ_MINWEST]
 3:
        mov     x0, xzr
@@ -102,17 +102,17 @@ ENTRY(__kernel_clock_gettime)
        cbnz    use_syscall, 7f
 
        bl      __do_get_tspec
-       seqcnt_check w13, 1b
+       seqcnt_check w9, 1b
 
        cmp     w0, #CLOCK_MONOTONIC
        b.ne    6f
 
        /* Get wtm timespec. */
-       ldp     x14, x15, [vdso_data, #VDSO_WTM_CLK_SEC]
+       ldp     x13, x14, [vdso_data, #VDSO_WTM_CLK_SEC]
 
        /* Check the sequence counter. */
-       seqcnt_read w13
-       seqcnt_check w13, 1b
+       seqcnt_read w9
+       seqcnt_check w9, 1b
        b       4f
 2:
        cmp     w0, #CLOCK_REALTIME_COARSE
@@ -122,37 +122,37 @@ ENTRY(__kernel_clock_gettime)
        /* Get coarse timespec. */
        adr     vdso_data, _vdso_data
 3:     seqcnt_acquire
-       ldp     x9, x10, [vdso_data, #VDSO_XTIME_CRS_SEC]
+       ldp     x10, x11, [vdso_data, #VDSO_XTIME_CRS_SEC]
 
        /* Get wtm timespec. */
-       ldp     x14, x15, [vdso_data, #VDSO_WTM_CLK_SEC]
+       ldp     x13, x14, [vdso_data, #VDSO_WTM_CLK_SEC]
 
        /* Check the sequence counter. */
-       seqcnt_read w13
-       seqcnt_check w13, 3b
+       seqcnt_read w9
+       seqcnt_check w9, 3b
 
        cmp     w0, #CLOCK_MONOTONIC_COARSE
        b.ne    6f
 4:
        /* Add on wtm timespec. */
-       add     x9, x9, x14
-       add     x10, x10, x15
+       add     x10, x10, x13
+       add     x11, x11, x14
 
        /* Normalise the new timespec. */
-       mov     x14, #NSEC_PER_SEC_LO16
-       movk    x14, #NSEC_PER_SEC_HI16, lsl #16
-       cmp     x10, x14
+       mov     x15, #NSEC_PER_SEC_LO16
+       movk    x15, #NSEC_PER_SEC_HI16, lsl #16
+       cmp     x11, x15
        b.lt    5f
-       sub     x10, x10, x14
-       add     x9, x9, #1
+       sub     x11, x11, x15
+       add     x10, x10, #1
 5:
-       cmp     x10, #0
+       cmp     x11, #0
        b.ge    6f
-       add     x10, x10, x14
-       sub     x9, x9, #1
+       add     x11, x11, x15
+       sub     x10, x10, #1
 
 6:     /* Store to the user timespec. */
-       stp     x9, x10, [x1, #TSPEC_TV_SEC]
+       stp     x10, x11, [x1, #TSPEC_TV_SEC]
        mov     x0, xzr
        ret     x2
 7:
@@ -203,39 +203,39 @@ ENDPROC(__kernel_clock_getres)
  * Expects vdso_data to be initialised.
  * Clobbers the temporary registers (x9 - x15).
  * Returns:
- *  - (x9, x10) = (ts->tv_sec, ts->tv_nsec)
- *  - (x11, x12) = (xtime->tv_sec, xtime->tv_nsec)
- *  - w13 = vDSO sequence counter
+ *  - w9               = vDSO sequence counter
+ *  - (x10, x11)       = (ts->tv_sec, ts->tv_nsec)
+ *  - w12              = cs_shift
  */
 ENTRY(__do_get_tspec)
        .cfi_startproc
 
        /* Read from the vDSO data page. */
        ldr     x10, [vdso_data, #VDSO_CS_CYCLE_LAST]
-       ldp     x11, x12, [vdso_data, #VDSO_XTIME_CLK_SEC]
-       ldp     w14, w15, [vdso_data, #VDSO_CS_MULT]
-       seqcnt_read w13
+       ldp     x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC]
+       ldp     w11, w12, [vdso_data, #VDSO_CS_MULT]
+       seqcnt_read w9
 
        /* Read the physical counter. */
        isb
-       mrs     x9, cntpct_el0
+       mrs     x15, cntpct_el0
 
        /* Calculate cycle delta and convert to ns. */
-       sub     x10, x9, x10
+       sub     x10, x15, x10
        /* We can only guarantee 56 bits of precision. */
-       movn    x9, #0xff00, lsl #48
-       and     x10, x9, x10
-       mul     x10, x10, x14
-       lsr     x10, x10, x15
+       movn    x15, #0xff00, lsl #48
+       and     x10, x15, x10
+       mul     x10, x10, x11
+       lsr     x10, x10, x12
 
        /* Use the kernel time to calculate the new timespec. */
-       add     x10, x12, x10
-       mov     x14, #NSEC_PER_SEC_LO16
-       movk    x14, #NSEC_PER_SEC_HI16, lsl #16
-       udiv    x15, x10, x14
-       add     x9, x15, x11
-       mul     x14, x14, x15
-       sub     x10, x10, x14
+       mov     x11, #NSEC_PER_SEC_LO16
+       movk    x11, #NSEC_PER_SEC_HI16, lsl #16
+       add     x15, x10, x14
+       udiv    x14, x15, x11
+       add     x10, x13, x14
+       mul     x13, x14, x11
+       sub     x11, x15, x13
 
        ret
        .cfi_endproc