firmware: Reset all the general purpose registers to zero.

A warm reset by pressing the reset button may not initialize all the
registers to zero. Do it for every hart during warm boot.

Signed-off-by: Atish Patra <atish.patra@wdc.com>

diff --git a/firmware/fw_base.S b/firmware/fw_base.S
index 83fe2aa..1725a92 100644 (file)
--- a/firmware/fw_base.S
+++ b/firmware/fw_base.S
@@ -120,6 +120,9 @@ _wait_for_boot_hart:
        beqz    a5, _wait_for_boot_hart
 
 _start_warm:
+       li      ra, 0
+       call    _reset_regs
+
        /* Disable and clear all interrupts */
        csrw    CSR_MIE, zero
        csrw    CSR_MIP, zero
@@ -380,3 +383,41 @@ _trap_handler_all_mode:
        REG_L   sp, SBI_TRAP_REGS_OFFSET(sp)(sp)
 
        mret
+
+       .align 3
+       .section .entry, "ax", %progbits
+       .globl _reset_regs
+_reset_regs:
+
+       /* Reset all registers except ra, a0,a1 */
+       li sp, 0
+       li gp, 0
+       li tp, 0
+       li t0, 0
+       li t1, 0
+       li t2, 0
+       li s0, 0
+       li s1, 0
+       li a2, 0
+       li a3, 0
+       li a4, 0
+       li a5, 0
+       li a6, 0
+       li a7, 0
+       li s2, 0
+       li s3, 0
+       li s4, 0
+       li s5, 0
+       li s6, 0
+       li s7, 0
+       li s8, 0
+       li s9, 0
+       li s10, 0
+       li s11, 0
+       li t3, 0
+       li t4, 0
+       li t5, 0
+       li t6, 0
+       csrw CSR_MSCRATCH, 0
+
+       ret