openrisc: Cleanup emergency print handling

The emergency print support only works for 8250 compatible serial ports.
Now that OpenRISC platforms may be configured with different serial port
hardware we don't want emergency print to try to print to non-existent
hardware which will cause lockups.

This patch contains several fixes to get emergency print working again:

 - Update symbol loading to not assume the location of symbols
 - Split the putc print operation out to its own function to allow
   for different future implementations.
 - Update _emergency_print_nr and _emergency_print to use the putc
   function.
 - Guard serial 8250 specific sequences by CONFIG_SERIAL_8250
 - Update string line feed from lf,cr to cr,lf.

Signed-off-by: Stafford Horne <shorne@gmail.com>

diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index 15f1b38..7bfa6e4 100644 (file)
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -297,19 +297,23 @@
        /* temporary store r3, r9 into r1, r10 */               ;\
        l.addi  r1,r3,0x0                                       ;\
        l.addi  r10,r9,0x0                                      ;\
-       /* the string referenced by r3 must be low enough */    ;\
+       LOAD_SYMBOL_2_GPR(r9,_string_unhandled_exception)       ;\
+       tophys  (r3,r9)                                         ;\
        l.jal   _emergency_print                                ;\
-       l.ori   r3,r0,lo(_string_unhandled_exception)           ;\
+        l.nop                                                  ;\
        l.mfspr r3,r0,SPR_NPC                                   ;\
        l.jal   _emergency_print_nr                             ;\
-       l.andi  r3,r3,0x1f00                                    ;\
-       /* the string referenced by r3 must be low enough */    ;\
+        l.andi r3,r3,0x1f00                                    ;\
+       LOAD_SYMBOL_2_GPR(r9,_string_epc_prefix)                ;\
+       tophys  (r3,r9)                                         ;\
        l.jal   _emergency_print                                ;\
-       l.ori   r3,r0,lo(_string_epc_prefix)                    ;\
+        l.nop                                                  ;\
        l.jal   _emergency_print_nr                             ;\
-       l.mfspr r3,r0,SPR_EPCR_BASE                             ;\
+        l.mfspr r3,r0,SPR_EPCR_BASE                            ;\
+       LOAD_SYMBOL_2_GPR(r9,_string_nl)                        ;\
+       tophys  (r3,r9)                                         ;\
        l.jal   _emergency_print                                ;\
-       l.ori   r3,r0,lo(_string_nl)                            ;\
+        l.nop                                                  ;\
        /* end of printing */                                   ;\
        l.addi  r3,r1,0x0                                       ;\
        l.addi  r9,r10,0x0                                      ;\
@@ -1530,65 +1534,99 @@ trampoline_out:
        l.jr    r9
        l.nop
 
-
 /*
- * DSCR: prints a string referenced by r3.
+ * DESC: Prints ASCII character stored in r7
  *
- * PRMS: r3            - address of the first character of null
- *                     terminated string to be printed
+ * PRMS: r7    - a 32-bit value with an ASCII character in the first byte
+ *             position.
  *
- * PREQ: UART at UART_BASE_ADD has to be initialized
+ * PREQ: The UART at UART_BASE_ADD has to be initialized
  *
- * POST: caller should be aware that r3, r9 are changed
+ * POST: internally used but restores:
+ *      r4     - to store UART_BASE_ADD
+ *      r5     - for loading OFF_TXFULL / THRE,TEMT
+ *      r6     - for storing bitmask (SERIAL_8250)
  */
-ENTRY(_emergency_print)
+ENTRY(_emergency_putc)
        EMERGENCY_PRINT_STORE_GPR4
        EMERGENCY_PRINT_STORE_GPR5
        EMERGENCY_PRINT_STORE_GPR6
-       EMERGENCY_PRINT_STORE_GPR7
-2:
-       l.lbz   r7,0(r3)
-       l.sfeq  r7,r0
-       l.bf    9f
-       l.nop
 
-// putc:
        l.movhi r4,hi(UART_BASE_ADD)
+       l.ori   r4,r4,lo(UART_BASE_ADD)
 
+#if defined(CONFIG_SERIAL_8250)
+       /* Check UART LSR THRE (hold) bit */
        l.addi  r6,r0,0x20
 1:      l.lbz   r5,5(r4)
        l.andi  r5,r5,0x20
        l.sfeq  r5,r6
        l.bnf   1b
-       l.nop
+        l.nop
 
+       /* Write character */
        l.sb    0(r4),r7
 
+       /* Check UART LSR THRE|TEMT (hold, empty) bits */
        l.addi  r6,r0,0x60
 1:      l.lbz   r5,5(r4)
        l.andi  r5,r5,0x60
        l.sfeq  r5,r6
        l.bnf   1b
-       l.nop
+        l.nop
+#endif
+       EMERGENCY_PRINT_LOAD_GPR6
+       EMERGENCY_PRINT_LOAD_GPR5
+       EMERGENCY_PRINT_LOAD_GPR4
+       l.jr    r9
+        l.nop
+
+/*
+ * DSCR: prints a string referenced by r3.
+ *
+ * PRMS: r3            - address of the first character of null
+ *                     terminated string to be printed
+ *
+ * PREQ: UART at UART_BASE_ADD has to be initialized
+ *
+ * POST: caller should be aware that r3, r9 are changed
+ */
+ENTRY(_emergency_print)
+       EMERGENCY_PRINT_STORE_GPR7
+       EMERGENCY_PRINT_STORE_GPR9
+
+       /* Load character to r7, check for null terminator */
+2:     l.lbz   r7,0(r3)
+       l.sfeqi r7,0x0
+       l.bf    9f
+        l.nop
+
+       l.jal   _emergency_putc
+        l.nop
 
        /* next character */
        l.j     2b
-       l.addi  r3,r3,0x1
+        l.addi r3,r3,0x1
 
 9:
+       EMERGENCY_PRINT_LOAD_GPR9
        EMERGENCY_PRINT_LOAD_GPR7
-       EMERGENCY_PRINT_LOAD_GPR6
-       EMERGENCY_PRINT_LOAD_GPR5
-       EMERGENCY_PRINT_LOAD_GPR4
        l.jr    r9
-       l.nop
+        l.nop
 
+/*
+ * DSCR: prints a number in r3 in hex.
+ *
+ * PRMS: r3            - a 32-bit unsigned integer
+ *
+ * PREQ: UART at UART_BASE_ADD has to be initialized
+ *
+ * POST: caller should be aware that r3, r9 are changed
+ */
 ENTRY(_emergency_print_nr)
-       EMERGENCY_PRINT_STORE_GPR4
-       EMERGENCY_PRINT_STORE_GPR5
-       EMERGENCY_PRINT_STORE_GPR6
        EMERGENCY_PRINT_STORE_GPR7
        EMERGENCY_PRINT_STORE_GPR8
+       EMERGENCY_PRINT_STORE_GPR9
 
        l.addi  r8,r0,32                // shift register
 
@@ -1600,58 +1638,39 @@ ENTRY(_emergency_print_nr)
        /* don't skip the last zero if number == 0x0 */
        l.sfeqi r8,0x4
        l.bf    2f
-       l.nop
+        l.nop
 
        l.sfeq  r7,r0
        l.bf    1b
-       l.nop
+        l.nop
 
 2:
        l.srl   r7,r3,r8
 
        l.andi  r7,r7,0xf
        l.sflts r8,r0
-       l.bf    9f
+        l.bf   9f
 
+       /* Numbers greater than 9 translate to a-f */
        l.sfgtui r7,0x9
        l.bnf   8f
-       l.nop
+        l.nop
        l.addi  r7,r7,0x27
 
-8:
-       l.addi  r7,r7,0x30
-// putc:
-       l.movhi r4,hi(UART_BASE_ADD)
-
-       l.addi  r6,r0,0x20
-1:      l.lbz   r5,5(r4)
-       l.andi  r5,r5,0x20
-       l.sfeq  r5,r6
-       l.bnf   1b
-       l.nop
-
-       l.sb    0(r4),r7
-
-       l.addi  r6,r0,0x60
-1:      l.lbz   r5,5(r4)
-       l.andi  r5,r5,0x60
-       l.sfeq  r5,r6
-       l.bnf   1b
-       l.nop
+       /* Convert to ascii and output character */
+8:     l.jal   _emergency_putc
+        l.addi r7,r7,0x30
 
        /* next character */
        l.j     2b
        l.addi  r8,r8,-0x4
 
 9:
+       EMERGENCY_PRINT_LOAD_GPR9
        EMERGENCY_PRINT_LOAD_GPR8
        EMERGENCY_PRINT_LOAD_GPR7
-       EMERGENCY_PRINT_LOAD_GPR6
-       EMERGENCY_PRINT_LOAD_GPR5
-       EMERGENCY_PRINT_LOAD_GPR4
        l.jr    r9
-       l.nop
-
+        l.nop
 
 /*
  * This should be used for debugging only.
@@ -1676,7 +1695,9 @@ ENTRY(_emergency_print_nr)
 
 ENTRY(_early_uart_init)
        l.movhi r3,hi(UART_BASE_ADD)
+       l.ori   r3,r3,lo(UART_BASE_ADD)
 
+#if defined(CONFIG_SERIAL_8250)
        l.addi  r4,r0,0x7
        l.sb    0x2(r3),r4
 
@@ -1694,9 +1715,10 @@ ENTRY(_early_uart_init)
        l.addi  r4,r0,((UART_DIVISOR) & 0x000000ff)
        l.sb    UART_DLL(r3),r4
        l.sb    0x3(r3),r5
+#endif
 
        l.jr    r9
-       l.nop
+        l.nop
 
        .align  0x1000
        .global _secondary_evbar
@@ -1711,13 +1733,13 @@ _secondary_evbar:
 
        .section .rodata
 _string_unhandled_exception:
-       .string "\n\rRunarunaround: Unhandled exception 0x\0"
+       .string "\r\nRunarunaround: Unhandled exception 0x\0"
 
 _string_epc_prefix:
        .string ": EPC=0x\0"
 
 _string_nl:
-       .string "\n\r\0"
+       .string "\r\n\0"
 
 
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