riscv: doc: Add relative doc to describe RISC-V
Add documents to describe NX25 and AE250.
Also update other documents for RISC-V.
Signed-off-by: Rick Chen <rick@andestech.com>
Signed-off-by: Rick Chen <rickchen36@gmail.com>
Signed-off-by: Greentime Hu <green.hu@gmail.com>
diff --git a/README b/README
index 06f3ed0..b53ea7d 100644
--- a/README
+++ b/README
@@ -143,6 +143,7 @@
/nios2 Files generic to Altera NIOS2 architecture
/openrisc Files generic to OpenRISC architecture
/powerpc Files generic to PowerPC architecture
+ /riscv Files generic to RISC-V architecture
/sandbox Files generic to HW-independent "sandbox"
/sh Files generic to SH architecture
/x86 Files generic to x86 architecture
@@ -3510,7 +3511,7 @@
globally (CONFIG_CMD_MEMORY).
- CONFIG_SKIP_LOWLEVEL_INIT
- [ARM, NDS32, MIPS only] If this variable is defined, then certain
+ [ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
low level initializations (like setting up the memory
controller) are omitted and/or U-Boot does not
relocate itself into RAM.
@@ -4964,6 +4965,22 @@
NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
or current versions of GCC may "optimize" the code too much.
+On RISC-V, the following registers are used:
+
+ x0: hard-wired zero (zero)
+ x1: return address (ra)
+ x2: stack pointer (sp)
+ x3: global pointer (gp)
+ x4: thread pointer (tp)
+ x5: link register (t0)
+ x8: frame pointer (fp)
+ x10-x11: arguments/return values (a0-1)
+ x12-x17: arguments (a2-7)
+ x28-31: temporaries (t3-6)
+ pc: program counter (pc)
+
+ ==> U-Boot will use gp to hold a pointer to the global data
+
Memory Management:
------------------