improve port robustness, portability, and CSR handling

- removed tx_port.h dependency from .S files
- replaced tx_timer_interrupt.c with tx_timer_interrupt.S
-  made some cleanups, formatting to better readability
- removed macros (LOAD/STORE/REGBYTES)
  changed register nomenclature to use RISC-V ABI
  names (ra, sp, t0, etc.)
- added readme_threadx.txt

Signed-off-by: Akif Ejaz <akif.ejaz@10xengineers.ai>

Author: akifejaz

ports/risc-v64/gnu/CMakeLists.txt

@@ -9,7 +9,7 @@ target_sources(${PROJECT_NAME}
 	${CMAKE_CURRENT_LIST_DIR}/src/tx_thread_schedule.S
 	${CMAKE_CURRENT_LIST_DIR}/src/tx_thread_stack_build.S
 	${CMAKE_CURRENT_LIST_DIR}/src/tx_thread_system_return.S
-	${CMAKE_CURRENT_LIST_DIR}/src/tx_timer_interrupt.c
+	${CMAKE_CURRENT_LIST_DIR}/src/tx_timer_interrupt.S
     # {{END_TARGET_SOURCES}}
 )
 

ports/risc-v64/gnu/inc/tx_port.h

@@ -53,26 +53,6 @@
 #ifndef TX_PORT_H
 #define TX_PORT_H
 
-#ifdef __ASSEMBLER__
-
-
-#if __riscv_xlen == 64
-# define SLL32    sllw
-# define STORE    sd
-# define LOAD     ld
-# define LWU      lwu
-# define LOG_REGBYTES 3
-#else
-# define SLL32    sll
-# define STORE    sw
-# define LOAD     lw
-# define LWU      lw
-# define LOG_REGBYTES 2
-#endif
-#define REGBYTES (1 << LOG_REGBYTES)
-
-#else   /*not __ASSEMBLER__ */
-
 /* Include for memset.  */
 #include <string.h>
 
@@ -86,10 +66,7 @@
    alternately be defined on the command line.  */
 
 #include "tx_user.h"
-#endif
-
-
-/* Define compiler library include files.  */
+#endif /* TX_INCLUDE_USER_DEFINE_FILE */
 
 
 /* Define ThreadX basic types for this port.  */
@@ -105,8 +82,6 @@ typedef unsigned long long                      ULONG64;
 typedef short                                   SHORT;
 typedef unsigned short                          USHORT;
 #define ULONG64_DEFINED
-#define ALIGN_TYPE_DEFINED
-#define ALIGN_TYPE                              ULONG64
 
 
 
@@ -253,25 +228,25 @@ typedef unsigned short                          USHORT;
    is used to define a local function save area for the disable and restore
    macros.  */
 
-#ifdef TX_DISABLE_INLINE
+/* Expose helper used to perform an atomic read/modify/write of mstatus.
+   The helper composes and returns the posture per ThreadX contract. */
+UINT                                            _tx_thread_interrupt_control(UINT new_posture);
 
-ULONG64                                         _tx_thread_interrupt_control(unsigned int new_posture);
+#ifdef TX_DISABLE_INLINE
 
-#define TX_INTERRUPT_SAVE_AREA                  register ULONG64 interrupt_save;
+#define TX_INTERRUPT_SAVE_AREA                  register UINT interrupt_save;
 
 #define TX_DISABLE                              interrupt_save =  _tx_thread_interrupt_control(TX_INT_DISABLE);
 #define TX_RESTORE                              _tx_thread_interrupt_control(interrupt_save);
 
 #else
 
-#define TX_INTERRUPT_SAVE_AREA                  ULONG64 interrupt_save;
-/* Atomically read mstatus into interrupt_save and clear bit 3 of mstatus.  */
-#define TX_DISABLE                              {__asm__ ("csrrci %0, mstatus, 0x08" : "=r" (interrupt_save) : );};
-/* We only care about mstatus.mie (bit 3), so mask interrupt_save and write to mstatus.  */
-#define TX_RESTORE                              {register ULONG64 __tempmask = interrupt_save & 0x08; \
-                                                __asm__ ("csrrs x0, mstatus, %0 \n\t" : : "r" (__tempmask) : );};
+#define TX_INTERRUPT_SAVE_AREA                  register UINT interrupt_save;
 
-#endif
+#define TX_DISABLE                              interrupt_save =  _tx_thread_interrupt_control(TX_INT_DISABLE);
+#define TX_RESTORE                              _tx_thread_interrupt_control(interrupt_save);
+
+#endif /* TX_DISABLE_INLINE */
 
 
 /* Define the interrupt lockout macros for each ThreadX object.  */
@@ -291,7 +266,6 @@ CHAR                            _tx_version_id[] =
                                     "Copyright (c) 2024 Microsoft Corporation. * ThreadX RISC-V64/GNU Version 6.4.2 *";
 #else
 extern  CHAR                    _tx_version_id[];
-#endif
+#endif /* TX_THREAD_INIT */
 
-#endif   /*not __ASSEMBLER__ */
-#endif
+#endif /* TX_PORT_H */