lib: Disable the boot prints if SBI_SCRATCH_NO_BOOT_PRINTS is set

Use the newly introduced "options" in "struct sbi_scratch" to
conditionally disable the boot prints.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

docs/firmware/fw.md

@@ -75,3 +75,18 @@ make PLATFORM=<platform_subdir> FW_PAYLOAD_PATH=<payload path>
 The instructions to build each payload is different and the details can
 be found in the
 *docs/firmware/payload_<payload_name>.md* files.
+
+Options for OpenSBI Firmware behaviors
+--------------------------------------
+An optional compile time flag FW_OPTIONS can be used to control the OpenSBI
+firmware run-time behaviors.
+
+```
+make PLATFORM=<platform_subdir> FW_OPTIONS=<options>
+```
+
+FW_OPTIONS is a bitwise or'ed value of various options, eg: *FW_OPTIONS=0x1*
+stands for disabling boot prints from the OpenSBI library.
+
+For all supported options, please check "enum sbi_scratch_options" in the
+*include/sbi/sbi_scratch.h* header file.

include/sbi/sbi_scratch.h

@@ -70,6 +70,12 @@ struct sbi_scratch {
 	unsigned long options;
 } __packed;
 
+/** Possible options for OpenSBI library */
+enum sbi_scratch_options {
+	/** Disable prints during boot */
+	SBI_SCRATCH_NO_BOOT_PRINTS		= (1 << 0),
+};
+
 /** Get pointer to sbi_scratch for current HART */
 #define sbi_scratch_thishart_ptr()	\
 ((struct sbi_scratch *)csr_read(CSR_MSCRATCH))

lib/sbi_init.c

@@ -91,7 +91,8 @@ static void __noreturn init_coldboot(struct sbi_scratch *scratch, u32 hartid)
 	if (rc)
 		sbi_hart_hang();
 
-	sbi_boot_prints(scratch, hartid);
+	if (!(scratch->options & SBI_SCRATCH_NO_BOOT_PRINTS))
+		sbi_boot_prints(scratch, hartid);
 
 	if (!sbi_platform_has_hart_hotplug(plat))
 		sbi_hart_wake_coldboot_harts(scratch, hartid);