boards: others: neorv32: default to reading clock frequency at boot

Default to reading the clock frequency from SYSINFO at boot time to make
the board compatible with a wider range of NEORV32 implementations.

Signed-off-by: Henrik Brix Andersen <[email protected]>

Author: henrikbrixandersen

boards/others/neorv32/doc/index.rst

@@ -27,9 +27,10 @@ using :ref:`devicetree overlays <use-dt-overlays>`.
 System Clock
 ============
 
-The default board configuration assumes a system clock of 18 MHz. The clock
-frequency can be overridden by changing the ``clock-frequency`` property of the
-``cpu0`` devicetree node.
+The default board configuration reads the system clock frequency from the NEORV32 SYSINFO module,
+which results in a small run-time overhead. If the clock frequency is known at build time, this
+behavior can be overridden by setting the ``clock-frequency`` property of the ``cpu0`` devicetree
+node.
 
 CPU
 ===

boards/others/neorv32/neorv32.dts

@@ -7,7 +7,6 @@
 /dts-v1/;
 
 #include <neorv32.dtsi>
-#include <freq.h>
 #include <mem.h>
 
 / {
@@ -56,7 +55,6 @@
 
 &cpu0 {
 	riscv,isa = "rv32im_zicsr_zifencei";
-	clock-frequency = <DT_FREQ_M(18)>;
 };
 
 &bootrom {