bsp/tms570: use POM only when application image does not start at address 0.

Parameters overlay module is initialized and cleared first.
It is used later to replace exception target vectors
only if that is required.

The application loader code with CPU and SDRAM setup
code has to provide well defined pattern of instructions
at addresses 0x00000000 and 0x0000001f, because only data
read accesses can be processed reliably by POM. The expected
instruction pattern can be seen in the next example

  https://github.com/hornmich/tms570ls3137-hdk-sdram/blob/master/SDRAM_SCI_configuration/source/sys_intvecs.asm

Comments with detailed description of code, background
and reasons for selected approach have been included
in TMS570 bsp startup code.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Signed-off-by: Premysl Houdek <kom541000@gmail.com>

1 files changed, 90 insertions, 9 deletions

diff --git a/c/src/lib/libbsp/arm/tms570/pom/tms570-pom.c b/c/src/lib/libbsp/arm/tms570/pom/tms570-pom.c
index 749dd9d76f..6de64fe0f5 100644
--- a/c/src/lib/libbsp/arm/tms570/pom/tms570-pom.c
+++ b/c/src/lib/libbsp/arm/tms570/pom/tms570-pom.c
@@ -22,8 +22,61 @@
 #include <stdint.h>
 #include <bsp/tms570-pom.h>
 #include <bsp/linker-symbols.h>
+#include <rtems/score/armv4.h>
 #include <bsp.h>
 
+/*
+ * Placement of exceptions target addresses in memory
+ * when insructions with opcode 0xe59ff018
+ *      ldr pc, [pc, #0x18]
+ * are used to fill ARM exception vectors area
+ */
+typedef struct{
+  uint32_t reserved1;
+  uint32_t except_addr_undef;
+  uint32_t except_addr_swi;
+  uint32_t except_addr_prefetch;
+  uint32_t except_addr_abort;
+  uint32_t reserved2;
+  uint32_t except_addr_irq;
+  uint32_t except_addr_fiq;
+}vec_remap_table;
+
+void bsp_block_on_exception(void);
+
+void bsp_block_on_exception(void){
+  while(1);
+}
+
+extern char bsp_int_vec_overlay_start[];
+
+/*
+ * Global overlay target address holds shared MSB bits for all regions
+ * It is set to linker RAM_INT_VEC region - i.e. area reserved
+ * at internal SRAM memory start, address 0x08000000
+ */
+uint32_t pom_global_overlay_target_address_start =
+                                 (uintptr_t)bsp_int_vec_overlay_start;
+
+/**
+ * @brief initialize and clear parameters overlay module (POM)
+ *
+ * clears all remap regions. The actual POM enable is left to the first user.
+ *
+ * @retval Void
+ */
+void tms570_initialize_and_clear(void)
+{
+  int i;
+
+  TMS570_POM.GLBCTRL = 0 | (TMS570_POM_GLBCTRL_OTADDR(~0) &
+                            pom_global_overlay_target_address_start);
+
+  for ( i = 0; i < TMS570_POM_REGIONS; ++i ) {
+    TMS570_POM.REG[i].REGSIZE = TMS570_POM_REGSIZE_SIZE(TMS570_POM_REGSIZE_DISABLED);
+  }
+}
+
 /**
  * @brief remaps vector table
  *
@@ -33,22 +86,50 @@
  */
 void tms570_pom_remap(void)
 {
-  int i;
-  uint32_t vec_overlay_start = 0x08000000;
-  uint32_t temp = 0;
+  uint32_t vec_overlay_start = pom_global_overlay_target_address_start;
 
+  /*
+   * Copy RTEMS the first level exception processing code
+   * to RAM area which can be used for later as POM overlay
+   * of Flash vectors. The code is expected to have for of eight
+   *   ldr pc, [pc,#0x18]
+   * instructions followed by eight words with actual exception
+   * service routines target addresses. This is case of RTEMS default
+   * table found in
+   *   c/src/lib/libbsp/arm/shared/start/start.S
+   */
   memcpy((void*)vec_overlay_start, bsp_start_vector_table_begin, 64);
 
-  TMS570_POM.GLBCTRL = 0;
-
-  for ( i = 0; i < TMS570_POM_REGIONS; ++i ) {
-    TMS570_POM.REG[i].REGSIZE = TMS570_POM_REGSIZE_SIZE(TMS570_POM_REGSIZE_DISABLED);
+  #if 0
+  {
+    /* Fill exception table by catch error infinite loop for debugging */
+    vec_remap_table* vec_table = (vec_remap_table*)(vec_overlay_start+32);
+    vec_table->except_addr_undef = (uint32_t)bsp_block_on_exception;
+    vec_table->except_addr_swi = (uint32_t)bsp_block_on_exception;
+    vec_table->except_addr_prefetch = (uint32_t)bsp_block_on_exception;//_ARMV4_Exception_prefetch_abort;
+    vec_table->except_addr_abort = (uint32_t)bsp_block_on_exception;//_ARMV4_Exception_data_abort;
+    vec_table->except_addr_irq = (uint32_t)_ARMV4_Exception_interrupt;
+    vec_table->except_addr_fiq = (uint32_t)bsp_block_on_exception;//_ARMV4_Exception_interrupt;
   }
+  #endif
 
-  TMS570_POM.REG[0].PROGSTART = TMS570_POM_PROGSTART_STARTADDRESS(0);
+  /*
+   * The overlay vectors replacement area cannot be used directly
+   * to replace jump instructions on start of Flash because instruction
+   * fetch through POM is not reliable supported (works in most times
+   * but sometimes fails).
+   * Area of 64 bytes starting at address 0x00000040 is replaced.
+   * This way target addresses are placed between 0x00000060
+   * and 0x0000007F. If boot loader startup code contains instructions
+   *   ldr pc,[pc,#0x58]
+   * (opcode 0xe59ff058) then the jump target addresses are replaced
+   * by pointers to actual RTEMS exceptions service functions.
+   */
+  TMS570_POM.REG[0].PROGSTART = TMS570_POM_PROGSTART_STARTADDRESS(64);
   TMS570_POM.REG[0].OVLSTART = TMS570_POM_OVLSTART_STARTADDRESS(vec_overlay_start);
   TMS570_POM.REG[0].REGSIZE = TMS570_POM_REGSIZE_SIZE(TMS570_POM_REGSIZE_64B);
   TMS570_POM.GLBCTRL = TMS570_POM_GLBCTRL_ON_OFF(0xa) |
                        TMS570_POM_GLBCTRL_ETO(0xa) |
-                       (TMS570_POM_GLBCTRL_OTADDR(~0) & vec_overlay_start);
+                       (TMS570_POM_GLBCTRL_OTADDR(~0) &
+                        pom_global_overlay_target_address_start);
 }