Cold power on working!!!

Author: dgarske

hal/nxp_ppc.h

@@ -118,7 +118,16 @@
     #define ENABLE_L1_CACHE
     #define ENABLE_L2_CACHE
 
-    /* T2080 CPC SRAM config - 1MB for ECC P384 stack requirements */
+    /* L1 locked dcache as initial stack (16KB).
+     * CPC SRAM (via CoreNet) is unreliable on cold power cycle —
+     * store buffer drains cause bus errors. L1 locked cache is
+     * core-local and works reliably from first instruction.
+     * Address chosen below CPC SRAM range, no backing memory needed. */
+    #define L1_CACHE_ADDR (0xF8E00000UL)
+
+    /* T2080 CPC SRAM config - 1MB for ECC P384 stack requirements.
+     * CPC hardware is configured in early ASM but NOT used for stack.
+     * CPC SRAM becomes usable after cache hierarchy is initialized in C. */
     #define L2SRAM_ADDR   (0xF8F00000UL) /* CPC as SRAM (1MB) */
     #define L2SRAM_SIZE   (1024UL * 1024UL)
 

src/boot_ppc_start.S

@@ -934,7 +934,14 @@ cache_sram_init:
 setup_stack:
         /* Build top of stack address */
         /* Reserve 64 bytes of initial data (must be 16 byte aligned) */
+#ifdef L1_CACHE_ADDR
+        /* Use L1 locked dcache as initial stack (16KB).
+         * L1_CACHE_ADDR + 4*4KB = top of locked region.
+         * CPC SRAM is unreliable on cold power cycle (bus errors via CoreNet). */
+        LOAD_ADDR32(r1, L1_CACHE_ADDR + 0x4000 - 64)
+#else
         LOAD_ADDR32(r1, _end_stack-64)
+#endif
 
         /* PowerPC e500 Application Binary Interface User's Guide
          * 2.3.5.1.1 Minimal Stack Frame: No Local Variables or Saved Parameters
@@ -948,12 +955,12 @@ setup_stack:
         stwu    r1, -8(r1)   /* Save back chain and move SP */
         stw     r0, +12(r1)  /* Save return addr (underflow vect) */
 
+        uart_putc_debug 'D'             /* checkpoint D: stack ready */
         /* switch back to AS/TS=0, enable recoverable interrupts */
         lis     r3,     (MSR_CE | MSR_ME | MSR_DE | MSR_RI)@h
         ori     r3, r3, (MSR_CE | MSR_ME | MSR_DE | MSR_RI)@l
         mtmsr   r3
         isync
-        uart_putc_debug 'D'             /* checkpoint D: stack ready, entering C */
 
 #ifdef USE_GOT
         GET_GOT