[PATCH v6 0/5] RISC-V SBI debug console extension support

[PATCH v6 0/5] RISC-V SBI debug console extension support

[Anup Patel]

The SBI v2.0 specification is now frozen. The SBI v2.0 specification defines
SBI debug console (DBCN) extension which replaces the legacy SBI v0.1
functions sbi_console_putchar() and sbi_console_getchar().
(Refer v2.0-rc5 at https://github.com/riscv-non-isa/riscv-sbi-doc/releases)

This series adds support for SBI debug console (DBCN) extension in
Linux RISC-V.

To try these patches with KVM RISC-V, use KVMTOOL from the
riscv_zbx_zicntr_smstateen_condops_v1 branch at:
https://github.com/avpatel/kvmtool.git

These patches can also be found in the riscv_sbi_dbcn_v6 branch at:
https://github.com/avpatel/linux.git

Changes since v5:
 - Rebased on commit 9d1694dc91ce7b80bc96d6d8eaf1a1eca668d847
   ("Merge tag 'for-6.8/block-2024-01-18' of git://git.kernel.dk/linux")
 - Added Acked-by from GregKH in PATCH3 and PATCH4

Changes since v4:
 - Rebased on Linux-6.7-rc2
 - Addressed Drew's comments in PATCH2
 - Improved sbi_debug_console_write/read() to directly take virtual
   address of data so that virtual address to physical address
   conversion can be shared between tty/serial/earlycon-riscv-sbi.c
   and tty/hvc/hvc_riscv_sbi.c
 - Addressed Samuel's comments in PATCH3 and PATCH4

Changes since v3:
 - Rebased on Linux-6.7-rc1
 - Dropped PATCH1 to PATCH5 of v3 series since these were merged through
   KVM RISC-V tree for Linux-6.7
 - Used proper error code in PATCH1
 - Added new PATCH2 which add common SBI debug console helper functions
 - Updated PATCH3 and PATCH4 to use SBI debug console helper functions

Changes since v2:
 - Rebased on Linux-6.6-rc5
 - Handled page-crossing in PATCH7 of v2 series
 - Addressed Drew's comment in PATCH3 of v2 series
 - Added new PATCH5 to make get-reg-list test aware of SBI DBCN extension

Changes since v1:
 - Remove use of #ifdef from PATCH4 and PATCH5 of the v1 series
 - Improved commit description of PATCH3 in v1 series
 - Introduced new PATCH3 in this series to allow some SBI extensions
   (such as SBI DBCN) do to disabled by default so that older KVM user space
   work fine and newer KVM user space have to explicitly opt-in for emulating
   SBI DBCN.
 - Introduced new PATCH5 in this series which adds inline version of
   sbi_console_getchar() and sbi_console_putchar() for the case where
   CONFIG_RISCV_SBI_V01 is disabled.

Anup Patel (4):
  RISC-V: Add stubs for sbi_console_putchar/getchar()
  RISC-V: Add SBI debug console helper routines
  tty/serial: Add RISC-V SBI debug console based earlycon
  RISC-V: Enable SBI based earlycon support

Atish Patra (1):
  tty: Add SBI debug console support to HVC SBI driver

 arch/riscv/configs/defconfig            |  1 +
 arch/riscv/include/asm/sbi.h            | 10 ++++
 arch/riscv/kernel/sbi.c                 | 66 +++++++++++++++++++++++++
 drivers/tty/hvc/Kconfig                 |  2 +-
 drivers/tty/hvc/hvc_riscv_sbi.c         | 37 +++++++++++---
 drivers/tty/serial/Kconfig              |  2 +-
 drivers/tty/serial/earlycon-riscv-sbi.c | 27 ++++++++--
 7 files changed, 133 insertions(+), 12 deletions(-)

-- 
2.34.1

[PATCH v6 1/5] RISC-V: Add stubs for sbi_console_putchar/getchar()

[Anup Patel]

The functions sbi_console_putchar() and sbi_console_getchar() are
not defined when CONFIG_RISCV_SBI_V01 is disabled so let us add
stub of these functions to avoid "#ifdef" on user side.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---
 arch/riscv/include/asm/sbi.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index b6f898c56940..e0a8eca32ba5 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -288,8 +288,13 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
 			unsigned long arg3, unsigned long arg4,
 			unsigned long arg5);
 
+#ifdef CONFIG_RISCV_SBI_V01
 void sbi_console_putchar(int ch);
 int sbi_console_getchar(void);
+#else
+static inline void sbi_console_putchar(int ch) { }
+static inline int sbi_console_getchar(void) { return -ENOENT; }
+#endif
 long sbi_get_mvendorid(void);
 long sbi_get_marchid(void);
 long sbi_get_mimpid(void);
-- 
2.34.1

[PATCH v6 2/5] RISC-V: Add SBI debug console helper routines

[Anup Patel]

Let us provide SBI debug console helper routines which can be
shared by serial/earlycon-riscv-sbi.c and hvc/hvc_riscv_sbi.c.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---
 arch/riscv/include/asm/sbi.h |  5 +++
 arch/riscv/kernel/sbi.c      | 66 ++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index e0a8eca32ba5..13594efb24bd 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -351,6 +351,11 @@ static inline unsigned long sbi_mk_version(unsigned long major,
 }
 
 int sbi_err_map_linux_errno(int err);
+
+extern bool sbi_debug_console_available;
+ssize_t sbi_debug_console_write(const u8 *bytes, size_t num_bytes);
+ssize_t sbi_debug_console_read(u8 *bytes, size_t num_bytes);
+
 #else /* CONFIG_RISCV_SBI */
 static inline int sbi_remote_fence_i(const struct cpumask *cpu_mask) { return -1; }
 static inline void sbi_init(void) {}
diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
index 5a62ed1da453..b06ad29f54b5 100644
--- a/arch/riscv/kernel/sbi.c
+++ b/arch/riscv/kernel/sbi.c
@@ -7,6 +7,7 @@
 
 #include <linux/bits.h>
 #include <linux/init.h>
+#include <linux/mm.h>
 #include <linux/pm.h>
 #include <linux/reboot.h>
 #include <asm/sbi.h>
@@ -571,6 +572,66 @@ long sbi_get_mimpid(void)
 }
 EXPORT_SYMBOL_GPL(sbi_get_mimpid);
 
+bool sbi_debug_console_available;
+
+ssize_t sbi_debug_console_write(const u8 *bytes, size_t num_bytes)
+{
+	phys_addr_t base_addr;
+	struct sbiret ret;
+
+	if (!sbi_debug_console_available)
+		return -EOPNOTSUPP;
+
+	if (is_vmalloc_addr(bytes))
+		base_addr = page_to_phys(vmalloc_to_page(bytes)) +
+			    offset_in_page(bytes);
+	else
+		base_addr = __pa(bytes);
+	if (PAGE_SIZE < (offset_in_page(bytes) + num_bytes))
+		num_bytes = PAGE_SIZE - offset_in_page(bytes);
+
+	if (IS_ENABLED(CONFIG_32BIT))
+		ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
+				num_bytes, lower_32_bits(base_addr),
+				upper_32_bits(base_addr), 0, 0, 0);
+	else
+		ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
+				num_bytes, base_addr, 0, 0, 0, 0);
+
+	if (ret.error == SBI_ERR_FAILURE)
+		return -EIO;
+	return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;
+}
+
+ssize_t sbi_debug_console_read(u8 *bytes, size_t num_bytes)
+{
+	phys_addr_t base_addr;
+	struct sbiret ret;
+
+	if (!sbi_debug_console_available)
+		return -EOPNOTSUPP;
+
+	if (is_vmalloc_addr(bytes))
+		base_addr = page_to_phys(vmalloc_to_page(bytes)) +
+			    offset_in_page(bytes);
+	else
+		base_addr = __pa(bytes);
+	if (PAGE_SIZE < (offset_in_page(bytes) + num_bytes))
+		num_bytes = PAGE_SIZE - offset_in_page(bytes);
+
+	if (IS_ENABLED(CONFIG_32BIT))
+		ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ,
+				num_bytes, lower_32_bits(base_addr),
+				upper_32_bits(base_addr), 0, 0, 0);
+	else
+		ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ,
+				num_bytes, base_addr, 0, 0, 0, 0);
+
+	if (ret.error == SBI_ERR_FAILURE)
+		return -EIO;
+	return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;
+}
+
 void __init sbi_init(void)
 {
 	int ret;
@@ -612,6 +673,11 @@ void __init sbi_init(void)
 			sbi_srst_reboot_nb.priority = 192;
 			register_restart_handler(&sbi_srst_reboot_nb);
 		}
+		if ((sbi_spec_version >= sbi_mk_version(2, 0)) &&
+		    (sbi_probe_extension(SBI_EXT_DBCN) > 0)) {
+			pr_info("SBI DBCN extension detected\n");
+			sbi_debug_console_available = true;
+		}
 	} else {
 		__sbi_set_timer = __sbi_set_timer_v01;
 		__sbi_send_ipi	= __sbi_send_ipi_v01;
-- 
2.34.1

[PATCH v6 3/5] tty/serial: Add RISC-V SBI debug console based earlycon

[Anup Patel]

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@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/Kconfig              |  2 +-
 drivers/tty/serial/earlycon-riscv-sbi.c | 27 ++++++++++++++++++++++---
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 8b1f5756002f..ffcf4882b25f 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..0162155f0c83 100644
--- a/drivers/tty/serial/earlycon-riscv-sbi.c
+++ b/drivers/tty/serial/earlycon-riscv-sbi.c
@@ -15,17 +15,38 @@ 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);
 }
 
+static void sbi_dbcn_console_write(struct console *con,
+				   const char *s, unsigned int n)
+{
+	int ret;
+
+	while (n) {
+		ret = sbi_debug_console_write(s, n);
+		if (ret < 0)
+			break;
+
+		s += ret;
+		n -= ret;
+	}
+}
+
 static int __init early_sbi_setup(struct earlycon_device *device,
 				  const char *opt)
 {
-	device->con->write = sbi_console_write;
+	if (sbi_debug_console_available)
+		device->con->write = sbi_dbcn_console_write;
+	else if (IS_ENABLED(CONFIG_RISCV_SBI_V01))
+		device->con->write = sbi_0_1_console_write;
+	else
+		return -ENODEV;
+
 	return 0;
 }
 EARLYCON_DECLARE(sbi, early_sbi_setup);
-- 
2.34.1

[PATCH v6 4/5] tty: Add SBI debug console support to HVC SBI driver

[Anup Patel]

From: Atish Patra <atishp@rivosinc.com>

RISC-V SBI specification supports advanced debug console
support via SBI DBCN extension.

Extend the HVC SBI driver to support it.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/hvc/Kconfig         |  2 +-
 drivers/tty/hvc/hvc_riscv_sbi.c | 37 ++++++++++++++++++++++++++-------
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
index 4f9264d005c0..6e05c5c7bca1 100644
--- a/drivers/tty/hvc/Kconfig
+++ b/drivers/tty/hvc/Kconfig
@@ -108,7 +108,7 @@ config HVC_DCC_SERIALIZE_SMP
 
 config HVC_RISCV_SBI
 	bool "RISC-V SBI console support"
-	depends on RISCV_SBI_V01
+	depends on RISCV_SBI
 	select HVC_DRIVER
 	help
 	  This enables support for console output via RISC-V SBI calls, which
diff --git a/drivers/tty/hvc/hvc_riscv_sbi.c b/drivers/tty/hvc/hvc_riscv_sbi.c
index a72591279f86..cede8a572594 100644
--- a/drivers/tty/hvc/hvc_riscv_sbi.c
+++ b/drivers/tty/hvc/hvc_riscv_sbi.c
@@ -40,21 +40,44 @@ static ssize_t hvc_sbi_tty_get(uint32_t vtermno, u8 *buf, size_t count)
 	return i;
 }
 
-static const struct hv_ops hvc_sbi_ops = {
+static const struct hv_ops hvc_sbi_v01_ops = {
 	.get_chars = hvc_sbi_tty_get,
 	.put_chars = hvc_sbi_tty_put,
 };
 
-static int __init hvc_sbi_init(void)
+static ssize_t hvc_sbi_dbcn_tty_put(uint32_t vtermno, const u8 *buf, size_t count)
 {
-	return PTR_ERR_OR_ZERO(hvc_alloc(0, 0, &hvc_sbi_ops, 16));
+	return sbi_debug_console_write(buf, count);
 }
-device_initcall(hvc_sbi_init);
 
-static int __init hvc_sbi_console_init(void)
+static ssize_t hvc_sbi_dbcn_tty_get(uint32_t vtermno, u8 *buf, size_t count)
 {
-	hvc_instantiate(0, 0, &hvc_sbi_ops);
+	return sbi_debug_console_read(buf, count);
+}
+
+static const struct hv_ops hvc_sbi_dbcn_ops = {
+	.put_chars = hvc_sbi_dbcn_tty_put,
+	.get_chars = hvc_sbi_dbcn_tty_get,
+};
+
+static int __init hvc_sbi_init(void)
+{
+	int err;
+
+	if (sbi_debug_console_available) {
+		err = PTR_ERR_OR_ZERO(hvc_alloc(0, 0, &hvc_sbi_dbcn_ops, 256));
+		if (err)
+			return err;
+		hvc_instantiate(0, 0, &hvc_sbi_dbcn_ops);
+	} else if (IS_ENABLED(CONFIG_RISCV_SBI_V01)) {
+		err = PTR_ERR_OR_ZERO(hvc_alloc(0, 0, &hvc_sbi_v01_ops, 256));
+		if (err)
+			return err;
+		hvc_instantiate(0, 0, &hvc_sbi_v01_ops);
+	} else {
+		return -ENODEV;
+	}
 
 	return 0;
 }
-console_initcall(hvc_sbi_console_init);
+device_initcall(hvc_sbi_init);
-- 
2.34.1

[PATCH v6 5/5] RISC-V: Enable SBI based earlycon support

[Anup Patel]

Let us enable SBI based earlycon support in defconfig for both RV32
and RV64 so that "earlycon=sbi" can be used again.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---
 arch/riscv/configs/defconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
index 905881282a7c..eaf34e871e30 100644
--- a/arch/riscv/configs/defconfig
+++ b/arch/riscv/configs/defconfig
@@ -149,6 +149,7 @@ CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y
 CONFIG_SERIAL_OF_PLATFORM=y
 CONFIG_SERIAL_SH_SCI=y
+CONFIG_SERIAL_EARLYCON_RISCV_SBI=y
 CONFIG_VIRTIO_CONSOLE=y
 CONFIG_HW_RANDOM=y
 CONFIG_HW_RANDOM_VIRTIO=y
-- 
2.34.1

Re: [PATCH v6 0/5] RISC-V SBI debug console extension support

[patchwork-bot+linux-riscv]

Hello:

This series was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Fri, 19 Jan 2024 17:04:44 +0530 you wrote:
> The SBI v2.0 specification is now frozen. The SBI v2.0 specification defines
> SBI debug console (DBCN) extension which replaces the legacy SBI v0.1
> functions sbi_console_putchar() and sbi_console_getchar().
> (Refer v2.0-rc5 at https://github.com/riscv-non-isa/riscv-sbi-doc/releases)
> 
> This series adds support for SBI debug console (DBCN) extension in
> Linux RISC-V.
> 
> [...]

Here is the summary with links:
  - [v6,1/5] RISC-V: Add stubs for sbi_console_putchar/getchar()
    https://git.kernel.org/riscv/c/f503b167b660
  - [v6,2/5] RISC-V: Add SBI debug console helper routines
    (no matching commit)
  - [v6,3/5] tty/serial: Add RISC-V SBI debug console based earlycon
    https://git.kernel.org/riscv/c/c77bf3607a0f
  - [v6,4/5] tty: Add SBI debug console support to HVC SBI driver
    (no matching commit)
  - [v6,5/5] RISC-V: Enable SBI based earlycon support
    https://git.kernel.org/riscv/c/50942ad6ddb5

You are awesome, thank you!
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