dt: Fetch the CPU frequency as well

If the 'timebase-frequency' property is available under the 'cpus' node
from the DTB blob, it makes sense to try to fetch this value from there
instead of hardcoding it. For other use-cases, where this information is
not available through DT (e.g. ACPI on the VisionFive2 board), we will
have to hardcode it with a default value even if it's not the proper
one.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>

2 files changed, 21 insertions, 6 deletions

diff --git a/include/fbos/dt.h b/include/fbos/dt.h
index fd77c35..bbeb7cd 100644
--- a/include/fbos/dt.h
+++ b/include/fbos/dt.h
@@ -3,13 +3,21 @@
 
 #include <fbos/compiler.h>
 
-// Pair of addresses where the initrd is located in memory.
-struct initrd_addr {
-	uintptr_t start;
-	uintptr_t end;
+// Default value for the 'dt_info.cpu_freq' property if none could be retrieved.
+#define DEFAULT_CPU_FREQ 10000000
+
+// Holds all the information that we gather from the initial DeviceTree blob.
+struct dt_info {
+	// Ticks per second. If `get_dt_info` fails at setting this value, then
+	// `DEFAULT_CPU_FREQ` is used.
+	uint64_t cpu_freq;
+
+	// Start and end addresses of the initramfs blob as stored in memory.
+	uintptr_t initrd_start;
+	uintptr_t initrd_end;
 };
 
-// Returns the `initrd` addresses as parsed from the given DTB blob.
-struct initrd_addr find_dt_initrd_addr(uint32_t *dtb);
+// Set 'info' by parsing the given 'dtb' blob.
+void get_dt_info(uint32_t *dtb, struct dt_info *info);
 
 #endif // __FBOS_DT_H_
diff --git a/include/fbos/init.h b/include/fbos/init.h
index f0f1dce..9e0049e 100644
--- a/include/fbos/init.h
+++ b/include/fbos/init.h
@@ -2,6 +2,7 @@
 #define __FBOS_INIT_H
 
 #include <fbos/compiler.h>
+#include <fbos/dt.h>
 #include <fbos/sched.h>
 
 // Tracks the amount of seconds that have elapsed since activating timer
@@ -10,6 +11,12 @@
 // Instantiated in kernel/trap.c, initialized in main.c.
 extern uint64_t seconds_elapsed;
 
+// General information from the DTB blob. This will be properly initialized at
+// the very beginning of kernel initialization.
+//
+// Instantiated and initialized in kernel/main.c.
+extern struct dt_info info;
+
 // Extract the executables from the initrd that is located at `base_addr` and
 // has the given `size`.
 void extract_initrd(const unsigned char *const base_addr, uint64_t size,