MIPS: start.S: optimize BSS initialization

Get the start and end address for clearing BSS from the newly
introduced symbols __bss_start and __bss_end. After GOT is
relocated, those symbols are already pointing to the correct
addresses.

Also optimize the loop by moving the address incrementation
to the delay slot to avoid the initial sub instruction.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

diff --git a/arch/mips/cpu/mips32/start.S b/arch/mips/cpu/mips32/start.S
index 7373d4e..cd8b914 100644 (file)
--- a/arch/mips/cpu/mips32/start.S
+++ b/arch/mips/cpu/mips32/start.S
@@ -228,17 +228,19 @@ in_ram:
        blt     t2, t3, 1b
         addi   t4, 4
 
-       /* Clear BSS */
-       lw      t1, -12(t0)             # t1 <-- uboot_end_data
-       lw      t2, -8(t0)              # t2 <-- uboot_end
-       add     t1, s1                  # adjust pointers
-       add     t2, s1
+       /*
+        * Clear BSS
+        *
+        * GOT is now relocated. Thus __bss_start and __bss_end can be
+        * accessed directly via $gp.
+        */
+       la      t1, __bss_start         # t1 <-- __bss_start
+       la      t2, __bss_end           # t2 <-- __bss_end
 
-       sub     t1, 4
 1:
-       addi    t1, 4
-       bltl    t1, t2, 1b
-        sw     zero, 0(t1)
+       sw      zero, 0(t1)
+       blt     t1, t2, 1b
+        addi   t1, 4
 
        move    a0, s0                  # a0 <-- gd
        la      t9, board_init_r

diff --git a/arch/mips/cpu/mips64/start.S b/arch/mips/cpu/mips64/start.S
index c0ae41a..ba4ca4d 100644 (file)
--- a/arch/mips/cpu/mips64/start.S
+++ b/arch/mips/cpu/mips64/start.S
@@ -220,17 +220,19 @@ in_ram:
        blt     t2, t3, 1b
         daddi  t8, 8
 
-       /* Clear BSS */
-       ld      t1, -24(t0)             # t1 <-- uboot_end_data
-       ld      t2, -16(t0)             # t2 <-- uboot_end
-       dadd    t1, s1                  # adjust pointers
-       dadd    t2, s1
+       /*
+        * Clear BSS
+        *
+        * GOT is now relocated. Thus __bss_start and __bss_end can be
+        * accessed directly via $gp.
+        */
+       dla     t1, __bss_start         # t1 <-- __bss_start
+       dla     t2, __bss_end           # t2 <-- __bss_end
 
-       dsub    t1, 8
 1:
-       daddi   t1, 8
-       bltl    t1, t2, 1b
-        sd     zero, 0(t1)
+       sd      zero, 0(t1)
+       blt     t1, t2, 1b
+        daddi  t1, 8
 
        move    a0, s0                  # a0 <-- gd
        dla     t9, board_init_r

diff --git a/arch/mips/cpu/xburst/start.S b/arch/mips/cpu/xburst/start.S
index 50b7fb1..bd9390a 100644 (file)
--- a/arch/mips/cpu/xburst/start.S
+++ b/arch/mips/cpu/xburst/start.S
@@ -143,16 +143,19 @@ in_ram:
        blt     t2, t3, 1b
         addi   t4, 4
 
-       /* Clear BSS */
-       lw      t1, -12(t0)             # t1 <-- uboot_end_data
-       lw      t2, -8(t0)              # t2 <-- uboot_end
-       add     t1, t6                  # adjust pointers
-       add     t2, t6
-
-       sub     t1, 4
-1:     addi    t1, 4
-       bltl    t1, t2, 1b
-        sw     zero, 0(t1)
+       /*
+        * Clear BSS
+        *
+        * GOT is now relocated. Thus __bss_start and __bss_end can be
+        * accessed directly via $gp.
+        */
+       la      t1, __bss_start         # t1 <-- __bss_start
+       la      t2, __bss_end           # t2 <-- __bss_end
+
+1:
+       sw      zero, 0(t1)
+       blt     t1, t2, 1b
+        addi   t1, 4
 
        move    a0, a1                  # a0 <-- gd
        la      t9, board_init_r