firmware: fw_base.S: Fix boot hart status synchronization

It's wrong to put the fence after setting the boot status flag because
all relocation operations must be finished before setting the status
flag. So, this fence must be put before the setting status flag, and
there is no use in putting a fence between _start_warm and setting
status flag.

Also, nop can't delay other harts too much, so use div instead, just
like Linux cpu_relax. Current opensbi force enables “M” Standard
Extension, and mul instructions have been used in the fw_base.S.

After the above two fixes, the boot hart index param of the
fw_dynamic_info could be guaranteed properly for all platforms.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Anup Patel <anup@brainfault.org>

diff --git a/firmware/fw_base.S b/firmware/fw_base.S
index 42b03fe890f0240e2bdc15ab357fd9a8c307e9ec..f7763f4d9e5640999331f6db61d2688439467927 100644 (file)
--- a/firmware/fw_base.S
+++ b/firmware/fw_base.S
@@ -399,8 +399,8 @@ _fdt_reloc_done:
        /* mark boot hart done */
        li      t0, BOOT_STATUS_BOOT_HART_DONE
        lla     t1, _boot_status
-       REG_S   t0, 0(t1)
        fence   rw, rw
+       REG_S   t0, 0(t1)
        j       _start_warm
 
        /* waiting for boot hart to be done (_boot_status == 2) */
@@ -409,9 +409,9 @@ _wait_for_boot_hart:
        lla     t1, _boot_status
        REG_L   t1, 0(t1)
        /* Reduce the bus traffic so that boot hart may proceed faster */
-       nop
-       nop
-       nop
+       div     t2, t2, zero
+       div     t2, t2, zero
+       div     t2, t2, zero
        bne     t0, t1, _wait_for_boot_hart
 
 _start_warm: