[PATCH 02/13] openrisc: Cleanup emergency print handling

Stafford Horne
2022-05-15T12:42:18Z

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>
---
arch/openrisc/kernel/head.S | 148 +++++++++++++++++++++---------------
1 file changed, 85 insertions(+), 63 deletions(-)

diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index 15f1b38dfe03..b1f3a65c271c 100644
--- 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)

+#elif 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"

/* ========================================[ page aligned structures ]=== */
--
2.31.1