[PATCH v4 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 <apa...@ventanamicro.com>
---
 arch/riscv/include/asm/sbi.h |  5 +++++
 arch/riscv/kernel/sbi.c      | 43 ++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 66f3933c14f6..ee7aef5f6233 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -334,6 +334,11 @@ static inline unsigned long sbi_mk_version(unsigned long 
major,
 }
 
 int sbi_err_map_linux_errno(int err);
+
+extern bool sbi_debug_console_available;
+int sbi_debug_console_write(unsigned int num_bytes, phys_addr_t base_addr);
+int sbi_debug_console_read(unsigned int num_bytes, phys_addr_t base_addr);
+
 #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..73a9c22c3945 100644
--- a/arch/riscv/kernel/sbi.c
+++ b/arch/riscv/kernel/sbi.c
@@ -571,6 +571,44 @@ long sbi_get_mimpid(void)
 }
 EXPORT_SYMBOL_GPL(sbi_get_mimpid);
 
+bool sbi_debug_console_available;
+
+int sbi_debug_console_write(unsigned int num_bytes, phys_addr_t base_addr)
+{
+       struct sbiret ret;
+
+       if (!sbi_debug_console_available)
+               return -EOPNOTSUPP;
+
+       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);
+
+       return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;
+}
+
+int sbi_debug_console_read(unsigned int num_bytes, phys_addr_t base_addr)
+{
+       struct sbiret ret;
+
+       if (!sbi_debug_console_available)
+               return -EOPNOTSUPP;
+
+       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);
+
+       return ret.error ? sbi_err_map_linux_errno(ret.error) : ret.value;
+}
+
 void __init sbi_init(void)
 {
        int ret;
@@ -612,6 +650,11 @@ 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