SAMA5: Change mapping of vector tables to work around that fact that I don't understand how the AXI MATRIX remap works

arch/arm/src/sama5/sam_boot.c

@@ -117,8 +117,37 @@ static const struct section_mapping_s section_mapping[] =
 {
   /* SAMA5 Internal Memories */
 
+  /* If CONFIG_ARCH_LOWVECTORS is defined, then the vectors located at the
+   * beginning of the .text region must appear at address zero.  There are
+   * two ways to accomplish this:
+   *
+   *   1. By explicitly mapping the beginning of .text region with a page
+   *      table entry so that the virtual address zero maps to the beginning
+   *      of the .text region.
+   *   2. A second way is to map the use the AXI MATRIX remap register to
+   *      map physical address zero to the beginning of the text region,
+   *      either internal SRAM or EBI CS 0.  Then we can set an identity
+   *      mapping to map the boot region at 0x0000:0000 to virtual address
+   *      0x0000:00000
+   *
+   * The first level bootloader is supposed to provide the AXI MATRIX
+   * mapping for us at boot time base on the state of the BMS pin.  However,
+   * I have found that in the test environments that I use, I cannot always
+   * be assured of that physical address mapping.
+   *
+   * So we do both here.  If we are exectuing from FLASH, then we provide
+   * the MMU to map the physical address of FLASH to address 0x0000:0000;
+   * if we are executing from the internal SRAM, then we trust the bootload
+   * to setup the AXI MATRIX mapping.
+   */
+
+#if defined(CONFIG_ARCH_LOWVECTORS) && !defined(CONFIG_SAMA5_BOOT_ISRAM)
+  { CONFIG_FLASH_VSTART, 0x00000000, MMU_ROMFLAGS, 1},
+#else
   { SAM_BOOTMEM_PSECTION, SAM_BOOTMEM_VSECTION,
     SAM_BOOTMEM_MMUFLAGS, SAM_BOOTMEM_NSECTIONS},
+#endif
+
   { SAM_ROM_PSECTION, SAM_ROM_VSECTION,
     SAM_ROM_MMUFLAGS, SAM_ROM_NSECTIONS},
   { SAM_NFCSRAM_PSECTION, SAM_NFCSRAM_VSECTION,

arch/arm/src/sama5/sam_irq.c

@@ -284,6 +284,12 @@ void up_irqinitialize(void)
   putreg32(AIC_WPMR_WPKEY | AIC_WPMR_WPEN, SAM_AIC_WPMR);
 
 #if defined(CONFIG_ARCH_LOWVECTORS) && defined(CONFIG_SAMA5_BOOT_ISRAM)
+  /* Disable MATRIX write protection */
+
+#if 0 /* Disabled on reset */
+  putreg32(MATRIX_WPMR_WPKEY, SAM_MATRIX_WPMR);
+#endif
+
   /* Set remap state 0 if we are running from internal SRAM.  If we booted
    * into NOR FLASH, then the first level bootloader should have already
    * provided this mapping for us.
@@ -306,6 +312,12 @@ void up_irqinitialize(void)
   putreg32(MATRIX_MRCR_RCB0, SAM_MATRIX_MRCR);   /* Enable remap */
   putreg32(AXIMX_REMAP_REMAP0, SAM_AXIMX_REMAP); /* Remap SRAM */
 
+  /* Restore MATRIX write protection */
+
+#if 0 /* Disabled on reset */
+  putreg32(MATRIX_WPMR_WPKEY | MATRIX_WPMR_WPEN, SAM_MATRIX_WPMR);
+#endif
+
   /* It might be wise to flush the instruction cache here */
 #endif
 

configs/sama5d3x-ek/README.txt

@@ -755,3 +755,7 @@ Configurations
        BMS jumper.
 
     STATUS:
+      2013-7-30:  I have been unable to execute this configuration from NOR
+        FLASH by closing the BMS jumper (J9).  As far as I can tell, this
+        jumper does nothing on my board???  I have been using the norboot
+        configuration to start the program in NOR FLASH (see just above).

configs/sama5d3x-ek/src/nor_main.c

@@ -129,6 +129,12 @@ int nor_main(int argc, char *argv)
 
   (void)irqdisable();
 
+  /* Disable MATRIX write protection */
+
+#if 0 /* Disabled on reset */
+  putreg32(MATRIX_WPMR_WPKEY, SAM_MATRIX_WPMR);
+#endif
+
   /* Set remap state 1.
    *
    *   Boot state:    ROM is seen at address 0x00000000
@@ -136,11 +142,20 @@ int nor_main(int argc, char *argv)
    *                  interface) instead of ROM.
    *   Remap State 1: HEBI is seen at address 0x00000000 (through AHB slave
    *                  interface) instead of ROM for external boot.
+   *
+   * REVISIT:  This does not work.  No matter what I do, the internal
+   * SRAM is always visible at address zero.  I am missing something.
    */
 
   putreg32(MATRIX_MRCR_RCB0, SAM_MATRIX_MRCR);   /* Enable remap */
   putreg32(AXIMX_REMAP_REMAP1, SAM_AXIMX_REMAP); /* Remap HEBI */
 
+  /* Restore MATRIX write protection */
+
+#if 0 /* Disabled on reset */
+  putreg32(MATRIX_WPMR_WPKEY | MATRIX_WPMR_WPEN, SAM_MATRIX_WPMR);
+#endif
+
   /* Disable the caches and the MMU.  Disabling the MMU should be safe here
    * because there is a 1-to-1 identity mapping between the physical and
    * virtual addressing.
@@ -163,16 +178,21 @@ int nor_main(int argc, char *argv)
 #ifdef SAMA5_NOR_START
   /* Then jump into NOR flash */
 
-//  printf("Jumping to NOR flash on CS0\n");
-//  fflush(stdout);
-//  usleep(500*1000);
+#if 0 /* Trying to printf() in this state is fatal */
+  printf("Jumping to NOR flash on CS0\n");
+  fflush(stdout);
+  usleep(500*1000);
+#endif
 
   NOR_ENTRY();
 #else
   /* Or just wait patiently for the user to break in with GDB. */
 
-//  printf("Waiting for GDB halt\n");
-//  fflush(stdout);
+#if 0 /* Trying to printf() in this state is fatal */
+  printf("Waiting for GDB halt\n");
+  fflush(stdout);
+#endif
+
   for (;;);
 #endif