firmware: fw_base: Introduce optional fw_platform_init()

We add optional fw_platform_init() function which will allow
platform specific code to update "struct sbi_platform platform"
before it is used.

The fw_platform_init() can be a regular C function so before
callint it we:
1. zero-out BSS section
2. Setup temporary trap handler to catch bugs
3. Setup temporary stack pointer

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>

diff --git a/firmware/fw_base.S b/firmware/fw_base.S
index 07edc74..5cb0dfa 100644 (file)
--- a/firmware/fw_base.S
+++ b/firmware/fw_base.S
@@ -160,6 +160,32 @@ _relocate_done:
        li      ra, 0
        call    _reset_regs
 
+       /* Zero-out BSS */
+       la      s4, _bss_start
+       la      s5, _bss_end
+_bss_zero:
+       REG_S   zero, (s4)
+       add     s4, s4, __SIZEOF_POINTER__
+       blt     s4, s5, _bss_zero
+
+       /* Setup temporary trap handler */
+       la      s4, _start_hang
+       csrw    CSR_MTVEC, s4
+
+       /* Setup temporary stack */
+       la      s4, _fw_end
+       li      s5, (SBI_SCRATCH_SIZE * 2)
+       add     sp, s4, s5
+
+       /*
+        * Initialize platform
+        * Note: The a0 to a4 registers passed to the
+        * firmware are parameters to this function.
+        */
+       MOV_5R  s0, a0, s1, a1, s2, a2, s3, a3, s4, a4
+       call    fw_platform_init
+       MOV_5R  a0, s0, a1, s1, a2, s2, a3, s3, a4, s4
+
        /* Allow main firmware to save info */
        MOV_5R  s0, a0, s1, a1, s2, a2, s3, a3, s4, a4
        call    fw_save_info
@@ -245,14 +271,6 @@ _scratch_init:
        add     t1, t1, t2
        blt     t1, s7, _scratch_init
 
-       /* Zero-out BSS */
-       la      a4, _bss_start
-       la      a5, _bss_end
-_bss_zero:
-       REG_S   zero, (a4)
-       add     a4, a4, __SIZEOF_POINTER__
-       blt     a4, a5, _bss_zero
-
        /* Override pervious arg1 */
        MOV_3R  s0, a0, s1, a1, s2, a2
        call    fw_prev_arg1
@@ -456,6 +474,13 @@ _start_hang:
 
        .section .entry, "ax", %progbits
        .align 3
+       .globl fw_platform_init
+       .weak fw_platform_init
+fw_platform_init:
+       ret
+
+       .section .entry, "ax", %progbits
+       .align 3
        .globl _trap_handler
 _trap_handler:
        /* Swap TP and MSCRATCH */