Hi,

I've been implementing pre-relocation malloc for MPC58xx to enable CONFIG_DM on our P1022 board (controlcenterd). The patch so far looks like this:

"

diff --git a/arch/powerpc/cpu/mpc85xx/cpu_init_early.c b/arch/powerpc/cpu/mpc85xx/cpu_init_early.c index 235a635..e6e1688 100644 --- a/arch/powerpc/cpu/mpc85xx/cpu_init_early.c +++ b/arch/powerpc/cpu/mpc85xx/cpu_init_early.c @@ -82,7 +82,6 @@ void setup_ifc(void) void cpu_init_early_f(void *fdt) { u32 mas0, mas1, mas2, mas3, mas7; - int i; #ifdef CONFIG_SYS_FSL_ERRATUM_P1010_A003549 ccsr_gur_t *gur = (void *)(CONFIG_SYS_MPC85xx_GUTS_ADDR); #endif @@ -95,13 +94,6 @@ void cpu_init_early_f(void *fdt) /* Pointer is writable since we allocated a register for it */ gd = (gd_t *) (CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_GBL_DATA_OFFSET);

- /* - * Clear initial global data - * we don't use memset so we can share this code with NAND_SPL - */ - for (i = 0; i < sizeof(gd_t); i++) - ((char *)gd)[i] = 0; - #ifdef CONFIG_QEMU_E500 /* * CONFIG_SYS_CCSRBAR_PHYS below may use gd->fdt_blob on ePAPR systems, diff --git a/arch/powerpc/cpu/mpc85xx/start.S b/arch/powerpc/cpu/mpc85xx/start.S index d867e2a..faf2804 100644 --- a/arch/powerpc/cpu/mpc85xx/start.S +++ b/arch/powerpc/cpu/mpc85xx/start.S @@ -1152,6 +1152,29 @@ _start_cont: /* Setup the stack in initial RAM,could be L2-as-SRAM or L1 dcache*/ lis r3,(CONFIG_SYS_INIT_RAM_ADDR)@h ori r3,r3,((CONFIG_SYS_INIT_SP_OFFSET-16)&~0xf)@l /* Align to 16 */ + +#ifdef CONFIG_SYS_MALLOC_F_LEN + /* Leave 16+ byte for back chain termination and NULL return address */ + subi r3,r3,((CONFIG_SYS_MALLOC_F_LEN+16+15)&~0xf) + + /* End of RAM */ + lis r4,(CONFIG_SYS_INIT_RAM_ADDR)@h + ori r4,r4,(CONFIG_SYS_INIT_RAM_SIZE)@l + + li r0,0 + +1: subi r4,r4,4 + stw r0,0(r4) + cmplw r4,r3 + bne 1b + + lis r4,(CONFIG_SYS_INIT_RAM_ADDR)@h + ori r4,r4,(CONFIG_SYS_GBL_DATA_OFFSET)@l + + addi r3,r3,16 /* Pre-relocation malloc area */ + stw r3,GD_MALLOC_BASE(r4) + subi r3,r3,16 +#endif li r0,0 stw r0,0(r3) /* Terminate Back Chain */ stw r0,+4(r3) /* NULL return address. */ -- 1.8.3

"

While tweaking the code, I found out that the board sometimes crashed and sometimes did not crash. As it turns out, the code I added had to have a specific length to work (the version above does not work, for example; but some additional nops are enough to make it work). I suspected an alignment issue somewhere below the function and traced it to the exception handlers that are defined there. Specifically, the timer_interrupt exception, since the following patch fixes the issue:

" diff --git a/arch/powerpc/cpu/mpc85xx/start.S b/arch/powerpc/cpu/mpc85xx/start.S index faf2804..d87c034 100644 --- a/arch/powerpc/cpu/mpc85xx/start.S +++ b/arch/powerpc/cpu/mpc85xx/start.S @@ -1240,6 +1240,7 @@ ProgramCheck: */ STD_EXCEPTION(0x0800, FPUnavailable, UnknownException) STD_EXCEPTION(0x0900, SystemCall, UnknownException) + . = 0x0a00 STD_EXCEPTION(0x0a00, Decrementer, timer_interrupt) STD_EXCEPTION(0x0b00, IntervalTimer, UnknownException) STD_EXCEPTION(0x0c00, WatchdogTimer, UnknownException) -- 1.8.3

"

Next, I ran a bisect (since the patch worked on v2015.01 without problems) and identified the commit 96d2bb952bbf2e5a14f6ad668312cbce3cc4485a (powerpc/mpc85xx: Don't relocate exception vectors) as the cause. Indeed, this commit removes the explicit alignment of the exceptions.

Possibly, some explicit alignment is needed after all?

Best regards,

Mario