[PATCH v2 06/13] include: sbi: Introduce nascent_init() platform callback

[Anup Patel <apatel@ventanamicro.com>]

We introduce nascent_init() platform callback which will allow
platforms to do very early initialization of platform specific
per-HART CSRs and per-HART devices.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
---
 include/sbi/sbi_platform.h | 20 ++++++++++++++++++++
 lib/sbi/sbi_init.c         |  8 ++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h
index 4d192f2..0b5ae4b 100644
--- a/include/sbi/sbi_platform.h
+++ b/include/sbi/sbi_platform.h
@@ -64,6 +64,9 @@ enum sbi_platform_features {
 
 /** Platform functions */
 struct sbi_platform_operations {
+	/* Platform nascent initialization */
+	int (*nascent_init)(void);
+
 	/** Platform early initialization */
 	int (*early_init)(bool cold_boot);
 	/** Platform final initialization */
@@ -299,6 +302,23 @@ static inline bool sbi_platform_hart_invalid(const struct sbi_platform *plat,
 	return FALSE;
 }
 
+/**
+ * Nascent (very early) initialization for current HART
+ *
+ * NOTE: This function can be used to do very early initialization of
+ * platform specific per-HART CSRs and devices.
+ *
+ * @param plat pointer to struct sbi_platform
+ *
+ * @return 0 on success and negative error code on failure
+ */
+static inline int sbi_platform_nascent_init(const struct sbi_platform *plat)
+{
+	if (plat && sbi_platform_ops(plat)->nascent_init)
+		return sbi_platform_ops(plat)->nascent_init();
+	return 0;
+}
+
 /**
  * Early initialization for current HART
  *
diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
index 83043c5..27d03a7 100644
--- a/lib/sbi/sbi_init.c
+++ b/lib/sbi/sbi_init.c
@@ -494,6 +494,14 @@ void __noreturn sbi_init(struct sbi_scratch *scratch)
 	if (next_mode_supported && atomic_xchg(&coldboot_lottery, 1) == 0)
 		coldboot = TRUE;
 
+	/*
+	 * Do platform specific nascent (very early) initialization so
+	 * that platform can initialize platform specific per-HART CSRs
+	 * or per-HART devices.
+	 */
+	if (sbi_platform_nascent_init(plat))
+		sbi_hart_hang();
+
 	if (coldboot)
 		init_coldboot(scratch, hartid);
 	else
-- 
2.25.1