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serial: Add a debug console using the RISC-V SBI interface

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The RISC-V SBI interface v0.1 provides a function for printing a
character to the console. Even though SBI v0.1 functions are deprecated,
the SBI console is quite useful for early debugging, because it works
without any dcache, memory, or MMIO access in S mode.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Samuel Holland 2021-09-12 10:56:09 -05:00 committed by Leo Yu-Chi Liang
parent 425c08faa8
commit 41f7be7334
3 changed files with 27 additions and 0 deletions
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10
drivers/serial/Kconfig
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@ -280,6 +280,14 @@ config DEBUG_EFI_CONSOLE
U-Boot when running on top of EFI (Extensive Firmware Interface).
This is a type of BIOS used by PCs.
config DEBUG_SBI_CONSOLE
bool "SBI"
depends on SBI_V01
help
Select this to enable a debug console which calls back to SBI to
output to the console. This can be useful for early debugging of
U-Boot when running on top of SBI (Supervisor Binary Interface).
config DEBUG_UART_S5P
bool "Samsung S5P"
depends on ARCH_EXYNOS || ARCH_S5PC1XX
@ -442,6 +450,7 @@ endchoice
config DEBUG_UART_BASE
hex "Base address of UART"
depends on DEBUG_UART
default 0 if DEBUG_SBI_CONSOLE
default 0 if DEBUG_UART_SANDBOX
help
This is the base address of your UART for memory-mapped UARTs.
@ -452,6 +461,7 @@ config DEBUG_UART_BASE
config DEBUG_UART_CLOCK
int "UART input clock"
depends on DEBUG_UART
default 0 if DEBUG_SBI_CONSOLE
default 0 if DEBUG_UART_SANDBOX
default 0 if DEBUG_MVEBU_A3700_UART
help

1
drivers/serial/Makefile
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@ -36,6 +36,7 @@ obj-$(CONFIG_ATMEL_USART) += atmel_usart.o
obj-$(CONFIG_BCM6345_SERIAL) += serial_bcm6345.o
obj-$(CONFIG_COREBOOT_SERIAL) += serial_coreboot.o
obj-$(CONFIG_CORTINA_UART) += serial_cortina.o
obj-$(CONFIG_DEBUG_SBI_CONSOLE) += serial_sbi.o
obj-$(CONFIG_EFI_APP) += serial_efi.o
obj-$(CONFIG_LPC32XX_HSUART) += lpc32xx_hsuart.o
obj-$(CONFIG_MCFUART) += serial_mcf.o

16
drivers/serial/serial_sbi.c Normal file
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@ -0,0 +1,16 @@
// SPDX-License-Identifier: GPL-2.0+
#include <debug_uart.h>
#include <asm/sbi.h>
static inline void _debug_uart_init(void)
{
}
static inline void _debug_uart_putc(int c)
{
if (CONFIG_IS_ENABLED(RISCV_SMODE))
sbi_console_putchar(c);
}
DEBUG_UART_FUNCS