[PATCH 4/6] tty/serial: Add RISC-V SBI debug console based earlycon

From: Anup Patel
Date: Tue Oct 10 2023 - 13:06:02 EST


We extend the existing RISC-V SBI earlycon support to use the new
RISC-V SBI debug console extension.

Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
---
drivers/tty/serial/Kconfig | 2 +-
drivers/tty/serial/earlycon-riscv-sbi.c | 35 ++++++++++++++++++++++---
2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index bdc568a4ab66..cec46091a716 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -87,7 +87,7 @@ config SERIAL_EARLYCON_SEMIHOST

config SERIAL_EARLYCON_RISCV_SBI
bool "Early console using RISC-V SBI"
- depends on RISCV_SBI_V01
+ depends on RISCV_SBI
select SERIAL_CORE
select SERIAL_CORE_CONSOLE
select SERIAL_EARLYCON
diff --git a/drivers/tty/serial/earlycon-riscv-sbi.c b/drivers/tty/serial/earlycon-riscv-sbi.c
index 27afb0b74ea7..b1da34e8d8cd 100644
--- a/drivers/tty/serial/earlycon-riscv-sbi.c
+++ b/drivers/tty/serial/earlycon-riscv-sbi.c
@@ -10,22 +10,49 @@
#include <linux/serial_core.h>
#include <asm/sbi.h>

+#ifdef CONFIG_RISCV_SBI_V01
static void sbi_putc(struct uart_port *port, unsigned char c)
{
sbi_console_putchar(c);
}

-static void sbi_console_write(struct console *con,
- const char *s, unsigned n)
+static void sbi_0_1_console_write(struct console *con,
+ const char *s, unsigned int n)
{
struct earlycon_device *dev = con->data;
uart_console_write(&dev->port, s, n, sbi_putc);
}
+#endif
+
+static void sbi_dbcn_console_write(struct console *con,
+ const char *s, unsigned int n)
+{
+ phys_addr_t pa = __pa(s);
+
+ sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
+#ifdef CONFIG_32BIT
+ n, pa, (u64)pa >> 32,
+#else
+ n, pa, 0,
+#endif
+ 0, 0, 0);
+}

static int __init early_sbi_setup(struct earlycon_device *device,
const char *opt)
{
- device->con->write = sbi_console_write;
- return 0;
+ int ret = 0;
+
+ if ((sbi_spec_version >= sbi_mk_version(2, 0)) &&
+ (sbi_probe_extension(SBI_EXT_DBCN) > 0))
+ device->con->write = sbi_dbcn_console_write;
+ else
+#ifdef CONFIG_RISCV_SBI_V01
+ device->con->write = sbi_0_1_console_write;
+#else
+ ret = -ENODEV;
+#endif
+
+ return ret;
}
EARLYCON_DECLARE(sbi, early_sbi_setup);
--
2.34.1