Console: Use callee-saved registers
This allows the console drivers to be implemented in C
Change-Id: Ibac859c4bcef0e92a0dcacc6b58ac19bc69b8342
Signed-off-by: Sathees Balya <sathees.balya@arm.com>
diff --git a/drivers/console/aarch64/multi_console.S b/drivers/console/aarch64/multi_console.S
index 0464776..7f076c6 100644
--- a/drivers/console/aarch64/multi_console.S
+++ b/drivers/console/aarch64/multi_console.S
@@ -39,10 +39,11 @@
* persistent memory (e.g. the data section).
* In : x0 - address of console_t structure
* Out: x0 - Always 1 (for easier tail calling)
- * Clobber list: x0, x1, x14, x15
+ * Clobber list: x0, x1
* -----------------------------------------------
*/
func console_register
+ stp x21, x30, [sp, #-16]!
#if ENABLE_ASSERTIONS
/* Assert that x0 isn't a NULL pointer */
cmp x0, #0
@@ -59,18 +60,17 @@
not_on_stack:
/* Assert that this struct isn't in the list */
mov x1, x0 /* Preserve x0 and x30 */
- mov x15, x30
bl console_is_registered
cmp x0, #0
ASM_ASSERT(eq)
- mov x30, x15
mov x0, x1
#endif /* ENABLE_ASSERTIONS */
- adrp x14, console_list
- ldr x1, [x14, :lo12:console_list] /* X1 = first struct in list */
- str x0, [x14, :lo12:console_list] /* list head = new console */
+ adrp x21, console_list
+ ldr x1, [x21, :lo12:console_list] /* X1 = first struct in list */
+ str x0, [x21, :lo12:console_list] /* list head = new console */
str x1, [x0, #CONSOLE_T_NEXT] /* new console next ptr = X1 */
mov x0, #1
+ ldp x21, x30, [sp], #16
ret
endfunc console_register
@@ -80,7 +80,7 @@
* of currently active consoles and remove it.
* In: x0 - address of console_t struct to remove
* Out: x0 - removed address, or NULL if not found
- * Clobber list: x0, x1, x14
+ * Clobber list: x0, x1
* -----------------------------------------------
*/
func console_unregister
@@ -89,25 +89,28 @@
cmp x0, #0
ASM_ASSERT(ne)
#endif /* ENABLE_ASSERTIONS */
- adrp x14, console_list
- add x14, x14, :lo12:console_list /* X14 = ptr to first struct */
- ldr x1, [x14] /* X1 = first struct */
+ stp x21, xzr, [sp, #-16]!
+ adrp x21, console_list
+ add x21, x21, :lo12:console_list /* X21 = ptr to first struct */
+ ldr x1, [x21] /* X1 = first struct */
unregister_loop:
cbz x1, unregister_not_found
cmp x0, x1
b.eq unregister_found
- ldr x14, [x14] /* X14 = next ptr of struct */
- ldr x1, [x14] /* X1 = next struct */
+ ldr x21, [x21] /* X21 = next ptr of struct */
+ ldr x1, [x21] /* X1 = next struct */
b unregister_loop
unregister_found:
ldr x1, [x1] /* X1 = next struct */
- str x1, [x14] /* prev->next = cur->next */
+ str x1, [x21] /* prev->next = cur->next */
+ ldp x21, xzr, [sp], #16
ret
unregister_not_found:
mov x0, #0 /* return NULL if not found */
+ ldp x21, xzr, [sp], #16
ret
endfunc console_unregister
@@ -117,7 +120,7 @@
* registered or not.
* In: x0 - address of console_t struct to remove
* Out: x0 - 1 if it is registered, 0 if not.
- * Clobber list: x0, x14
+ * Clobber list: x0
* -----------------------------------------------
*/
func console_is_registered
@@ -126,19 +129,22 @@
cmp x0, #0
ASM_ASSERT(ne)
#endif /* ENABLE_ASSERTIONS */
- adrp x14, console_list
- ldr x14, [x14, :lo12:console_list] /* X14 = first console struct */
+ stp x21, xzr, [sp, #-16]!
+ adrp x21, console_list
+ ldr x21, [x21, :lo12:console_list] /* X21 = first console struct */
check_registered_loop:
- cbz x14, console_not_registered /* Check if end of list */
- cmp x0, x14 /* Check if the pointers are different */
+ cbz x21, console_not_registered /* Check if end of list */
+ cmp x0, x21 /* Check if the pointers are different */
b.eq console_registered
- ldr x14, [x14, #CONSOLE_T_NEXT] /* Get pointer to next struct */
+ ldr x21, [x21, #CONSOLE_T_NEXT] /* Get pointer to next struct */
b check_registered_loop
console_not_registered:
mov x0, #0
+ ldp x21, xzr, [sp], #16
ret
console_registered:
mov x0, #1
+ ldp x21, xzr, [sp], #16
ret
endfunc console_is_registered
@@ -186,38 +192,41 @@
* In : x0 - character to be printed
* Out: x0 - printed character on success, or < 0
if at least one console had an error
- * Clobber list : x0, x1, x2, x12, x13, x14, x15
+ * Clobber list : x0, x1, x2
* ---------------------------------------------
*/
func console_putc
- mov x15, x30
- mov w13, #ERROR_NO_VALID_CONSOLE /* W13 = current return value */
- mov w12, w0 /* W12 = character to print */
- adrp x14, console_list
- ldr x14, [x14, :lo12:console_list] /* X14 = first console struct */
+ stp x21, x30, [sp, #-16]!
+ stp x19, x20, [sp, #-16]!
+ mov w20, #ERROR_NO_VALID_CONSOLE /* W20 = current return value */
+ mov w19, w0 /* W19 = character to print */
+ adrp x21, console_list
+ ldr x21, [x21, :lo12:console_list] /* X21 = first console struct */
putc_loop:
- cbz x14, putc_done
+ cbz x21, putc_done
adrp x1, console_state
ldrb w1, [x1, :lo12:console_state]
- ldr w2, [x14, #CONSOLE_T_FLAGS]
+ ldr w2, [x21, #CONSOLE_T_FLAGS]
tst w1, w2
b.eq putc_continue
- ldr x2, [x14, #CONSOLE_T_PUTC]
+ ldr x2, [x21, #CONSOLE_T_PUTC]
cbz x2, putc_continue
- mov w0, w12
- mov x1, x14
+ mov w0, w19
+ mov x1, x21
blr x2
- cmp w13, #ERROR_NO_VALID_CONSOLE /* update W13 if it's NOVALID */
+ cmp w20, #ERROR_NO_VALID_CONSOLE /* update W20 if it's NOVALID */
ccmp w0, #0, #0x8, ne /* else update it if W0 < 0 */
- csel w13, w0, w13, lt
+ csel w20, w0, w20, lt
putc_continue:
- ldr x14, [x14] /* X14 = next struct */
+ ldr x21, [x21] /* X21 = next struct */
b putc_loop
putc_done:
- mov w0, w13
- ret x15
+ mov w0, w20
+ ldp x19, x20, [sp], #16
+ ldp x21, x30, [sp], #16
+ ret
endfunc console_putc
/* ---------------------------------------------
@@ -230,42 +239,47 @@
* if all active consoles report real errors
* (other than just not having a char available).
* Out : x0 - read character, or < 0 on error
- * Clobber list : x0, x1, x13, x14, x15
+ * Clobber list : x0, x1
* ---------------------------------------------
*/
func console_getc
- mov x15, x30
+ stp x30, xzr, [sp, #-16]!
+ stp x20, x21, [sp, #-16]!
getc_try_again:
- mov w13, #ERROR_NO_VALID_CONSOLE /* W13 = current return value */
- adrp x14, console_list
- ldr x14, [x14, :lo12:console_list] /* X14 = first console struct */
- cbnz x14, getc_loop
- mov w0, w13 /* If no consoles registered */
- ret x15 /* return immediately. */
+ mov w20, #ERROR_NO_VALID_CONSOLE /* W20 = current return value */
+ adrp x21, console_list
+ ldr x21, [x21, :lo12:console_list] /* X21 = first console struct */
+ cbnz x21, getc_loop
+ mov w0, w20 /* If no consoles registered */
+ ldp x20, x21, [sp], #16
+ ldp x30, xzr, [sp], #16
+ ret /* return immediately. */
getc_loop:
adrp x0, console_state
ldrb w0, [x0, :lo12:console_state]
- ldr w1, [x14, #CONSOLE_T_FLAGS]
+ ldr w1, [x21, #CONSOLE_T_FLAGS]
tst w0, w1
b.eq getc_continue
- ldr x1, [x14, #CONSOLE_T_GETC]
+ ldr x1, [x21, #CONSOLE_T_GETC]
cbz x1, getc_continue
- mov x0, x14
+ mov x0, x21
blr x1
cmp w0, #0 /* if X0 >= 0: return */
b.ge getc_found
- cmp w13, #ERROR_NO_PENDING_CHAR /* may update W13 (NOCHAR has */
- csel w13, w13, w0, eq /* precedence vs real errors) */
+ cmp w20, #ERROR_NO_PENDING_CHAR /* may update W20 (NOCHAR has */
+ csel w20, w20, w0, eq /* precedence vs real errors) */
getc_continue:
- ldr x14, [x14] /* X14 = next struct */
- cbnz x14, getc_loop
- cmp w13, #ERROR_NO_PENDING_CHAR /* Keep scanning if at least */
+ ldr x21, [x21] /* X21 = next struct */
+ cbnz x21, getc_loop
+ cmp w20, #ERROR_NO_PENDING_CHAR /* Keep scanning if at least */
b.eq getc_try_again /* one console returns NOCHAR */
- mov w0, w13
+ mov w0, w20
getc_found:
- ret x15
+ ldp x20, x21, [sp], #16
+ ldp x30, xzr, [sp], #16
+ ret
endfunc console_getc
/* ---------------------------------------------
@@ -274,34 +288,37 @@
* data that hasn't been output. Calls all
* console's flush() handlers in succession.
* Out: x0 - 0 on success, < 0 if at least one error
- * Clobber list : x0, x1, x2, x3, x4, x5, x13, x14, x15
+ * Clobber list : x0, x1, x2
* ---------------------------------------------
*/
func console_flush
- mov x15, x30
- mov w13, #ERROR_NO_VALID_CONSOLE /* W13 = current return value */
- adrp x14, console_list
- ldr x14, [x14, :lo12:console_list] /* X14 = first console struct */
+ stp x30, xzr, [sp, #-16]!
+ stp x20, x21, [sp, #-16]!
+ mov w20, #ERROR_NO_VALID_CONSOLE /* W20 = current return value */
+ adrp x21, console_list
+ ldr x21, [x21, :lo12:console_list] /* X21 = first console struct */
flush_loop:
- cbz x14, flush_done
+ cbz x21, flush_done
adrp x1, console_state
ldrb w1, [x1, :lo12:console_state]
- ldr w2, [x14, #CONSOLE_T_FLAGS]
+ ldr w2, [x21, #CONSOLE_T_FLAGS]
tst w1, w2
b.eq flush_continue
- ldr x1, [x14, #CONSOLE_T_FLUSH]
+ ldr x1, [x21, #CONSOLE_T_FLUSH]
cbz x1, flush_continue
- mov x0, x14
+ mov x0, x21
blr x1
- cmp w13, #ERROR_NO_VALID_CONSOLE /* update W13 if it's NOVALID */
+ cmp w20, #ERROR_NO_VALID_CONSOLE /* update W20 if it's NOVALID */
ccmp w0, #0, #0x8, ne /* else update it if W0 < 0 */
- csel w13, w0, w13, lt
+ csel w20, w0, w20, lt
flush_continue:
- ldr x14, [x14] /* X14 = next struct */
+ ldr x21, [x21] /* X21 = next struct */
b flush_loop
flush_done:
- mov w0, w13
- ret x15
+ mov w0, w20
+ ldp x20, x21, [sp], #16
+ ldp x30, xzr, [sp], #16
+ ret
endfunc console_flush