[PATCH 03/13] openrisc: Add support for liteuart emergency printing

Stafford Horne
2022-05-15T12:42:20Z

This patch adds support for sending emergency print output, such as
unhandled exception details, to a liteuart serial device. This is the
default device available on litex platforms.

If a developer want to use this they should update UART_BASE_ADD
to the address of liteuart.

Signed-off-by: Stafford Horne <shorne@gmail.com>
---
arch/openrisc/kernel/head.S | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index b1f3a65c271c..21db50563f97 100644
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -1555,6 +1555,17 @@ ENTRY(_emergency_putc)
l.movhi r4,hi(UART_BASE_ADD)
l.ori r4,r4,lo(UART_BASE_ADD)

+#if defined(CONFIG_SERIAL_LITEUART)
+ /* Check OFF_TXFULL status */
+1: l.lwz r5,4(r4)
+ l.andi r5,r5,0xff
+ l.sfnei r5,0
+ l.bf 1b
+ l.nop
+
+ /* Write character */
+ l.andi r7,r7,0xff
+ l.sw 0(r4),r7
#elif defined(CONFIG_SERIAL_8250)
/* Check UART LSR THRE (hold) bit */
l.addi r6,r0,0x20
--
2.31.1