[PATCH v2 0/2] risc-v: implement DBCN based debug console

[PATCH v2 0/2] risc-v: implement DBCN based debug console

[Heinrich Schuchardt]

Currently we only offer an SBI based debug UART for SBI v0.1.
With OpenSBI 1.3 the Debug Console Extension (DBCN) has become available.
This allows us to implement a debug UART in a device independent manor.

v2:
	In the driver check that we are in S-mode.

Heinrich Schuchardt (2):
  risc-v: implement DBCN write byte
  risc-v: implement DBCN based debug console

 arch/riscv/include/asm/sbi.h |  1 +
 arch/riscv/lib/sbi.c         | 16 ++++++++++++++++
 drivers/serial/Kconfig       |  5 ++++-
 drivers/serial/serial_sbi.c  | 20 ++++++++++++++++++++
 4 files changed, 41 insertions(+), 1 deletion(-)

-- 
2.40.1

[PATCH v2 1/2] risc-v: implement DBCN write byte

[Heinrich Schuchardt]

The DBCN extension provides a Console Write Byte call.
Implement function sbi_dbcn_write_byte to invoke it.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
---
v2:
	no change
---
 arch/riscv/include/asm/sbi.h |  1 +
 arch/riscv/lib/sbi.c         | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 009a26885c..bf4c9af622 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -170,5 +170,6 @@ int sbi_get_mvendorid(long *mvendorid);
 int sbi_get_marchid(long *marchid);
 int sbi_get_mimpid(long *mimpid);
 void sbi_srst_reset(unsigned long type, unsigned long reason);
+int sbi_dbcn_write_byte(unsigned char ch);
 
 #endif
diff --git a/arch/riscv/lib/sbi.c b/arch/riscv/lib/sbi.c
index 8724e3a460..55a3bc3b5c 100644
--- a/arch/riscv/lib/sbi.c
+++ b/arch/riscv/lib/sbi.c
@@ -204,6 +204,22 @@ void sbi_srst_reset(unsigned long type, unsigned long reason)
 		  0, 0, 0, 0);
 }
 
+/**
+ * sbi_dbcn_write_byte() - write byte to debug console
+ *
+ * @ch:		byte to be written
+ * Return:	SBI error code (SBI_SUCCESS = 0 on success)
+ */
+int sbi_dbcn_write_byte(unsigned char ch)
+{
+	struct sbiret ret;
+
+	ret = sbi_ecall(SBI_EXT_DBCN,
+			SBI_EXT_DBCN_CONSOLE_WRITE_BYTE,
+			ch, 0, 0, 0, 0, 0);
+	return ret.error;
+}
+
 #ifdef CONFIG_SBI_V01
 
 /**
-- 
2.40.1

[PATCH v2 2/2] risc-v: implement DBCN based debug console

[Heinrich Schuchardt]

Use the DBCN SBI extension to implement a debug console.
Make it the default for S-mode RISC-V.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
---
v2:
	check that we are in S-mode
---
 drivers/serial/Kconfig      |  5 ++++-
 drivers/serial/serial_sbi.c | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 7ca42df6a7..fb108f0189 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -218,6 +218,7 @@ config DEBUG_UART
 choice
 	prompt "Select which UART will provide the debug UART"
 	depends on DEBUG_UART
+	default DEBUG_SBI_CONSOLE if RISCV_SMODE
 	default DEBUG_UART_NS16550
 
 config DEBUG_UART_ALTERA_JTAGUART
@@ -289,11 +290,13 @@ config DEBUG_EFI_CONSOLE
 
 config DEBUG_SBI_CONSOLE
 	bool "SBI"
-	depends on SBI_V01
+	depends on RISCV_SMODE
 	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).
+	  This implementation of the debug UART is not available while in
+	  M-mode (e.g. during SPL).
 
 config DEBUG_UART_S5P
 	bool "Samsung S5P"
diff --git a/drivers/serial/serial_sbi.c b/drivers/serial/serial_sbi.c
index b9f35ed36e..a51a96c1ef 100644
--- a/drivers/serial/serial_sbi.c
+++ b/drivers/serial/serial_sbi.c
@@ -3,6 +3,8 @@
 #include <debug_uart.h>
 #include <asm/sbi.h>
 
+#ifdef CONFIG_SBI_V01
+
 static inline void _debug_uart_init(void)
 {
 }
@@ -13,4 +15,22 @@ static inline void _debug_uart_putc(int c)
 		sbi_console_putchar(c);
 }
 
+#else
+
+static int sbi_dbcn_available;
+
+static inline void _debug_uart_init(void)
+{
+	if (CONFIG_IS_ENABLED(RISCV_SMODE))
+		sbi_dbcn_available = sbi_probe_extension(SBI_EXT_DBCN);
+}
+
+static inline void _debug_uart_putc(int ch)
+{
+	if (CONFIG_IS_ENABLED(RISCV_SMODE) && sbi_dbcn_available)
+		sbi_dbcn_write_byte(ch);
+}
+
+#endif
+
 DEBUG_UART_FUNCS
-- 
2.40.1

Re: [PATCH v2 2/2] risc-v: implement DBCN based debug console

[Leo Liang]

On Mon, Sep 04, 2023 at 01:24:04PM +0200, Heinrich Schuchardt wrote:
> Use the DBCN SBI extension to implement a debug console.
> Make it the default for S-mode RISC-V.
> 
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
> ---
> v2:
> 	check that we are in S-mode
> ---
>  drivers/serial/Kconfig      |  5 ++++-
>  drivers/serial/serial_sbi.c | 20 ++++++++++++++++++++
>  2 files changed, 24 insertions(+), 1 deletion(-)

Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

RE: [PATCH v2 0/2] risc-v: implement DBCN based debug console

[Chanho Park]

Hi,

> -----Original Message-----
> From: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
> Sent: Monday, September 4, 2023 8:24 PM
> To: Rick Chen <rick@andestech.com>; Leo <ycliang@andestech.com>
> Cc: Bin Meng <bmeng.cn@gmail.com>; Anup Patel <apatel@ventanamicro.com>;
> Chanho Park <chanho61.park@samsung.com>; u-boot@lists.denx.de; Heinrich
> Schuchardt <heinrich.schuchardt@canonical.com>
> Subject: [PATCH v2 0/2] risc-v: implement DBCN based debug console
> 
> Currently we only offer an SBI based debug UART for SBI v0.1.
> With OpenSBI 1.3 the Debug Console Extension (DBCN) has become available.
> This allows us to implement a debug UART in a device independent manor.
> 
> v2:
> 	In the driver check that we are in S-mode.

Thanks for the update. I've tested both patches on my VisionFive2 board.

Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Tested-by: Chanho Park <chanho61.park@samsung.com>

Best Regards,
Chanho Park