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openrisc: Add support for liteuart emergency printing

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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>
This commit is contained in:
Stafford Horne 2022-05-15 13:33:14 +09:00
parent e449759c24
commit 29bbb2a90f
1 changed files with 12 additions and 1 deletions
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13
arch/openrisc/kernel/head.S
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@ -1555,7 +1555,18 @@ ENTRY(_emergency_putc)
l.movhi r4,hi(UART_BASE_ADD)
l.ori r4,r4,lo(UART_BASE_ADD)
#if defined(CONFIG_SERIAL_8250)
#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
1: l.lbz r5,5(r4)