[U-Boot] [RFC v1 PATCH 1/1] mpc85xx: Enable pre-relocation malloc for MPC85xx

[York Sun <york.sun@nxp.com>]

On 03/30/2016 11:29 PM, Mario Six wrote:
> 
> Quoting York Sun <york.sun@nxp.com>:
> 
>> On 03/29/2016 11:53 PM, Mario Six wrote:
>>> To enable DM on MPC85xx, we need pre-relocation malloc, which is
>>> implemented in this patch.
>>>
>>> Signed-off-by: Mario Six <mario.six@gdsys.cc>
>>> Cc: York Sun <york.sun@nxp.com>
>>> Cc: Simon Glass <sjg@chromium.org>
>>> ---
>>>  arch/powerpc/cpu/mpc85xx/cpu_init_early.c |  8 --------
>>>  arch/powerpc/cpu/mpc85xx/start.S          | 28 ++++++++++++++++++++++++++++
>>>  2 files changed, 28 insertions(+), 8 deletions(-)
>>>
>>> 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..e6b5203 100644
>>> --- a/arch/powerpc/cpu/mpc85xx/start.S
>>> +++ b/arch/powerpc/cpu/mpc85xx/start.S
>>> @@ -1152,6 +1152,34 @@ _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
>>> +
>>> +	/* Fix issue with exception handler alignment */
>>> +	nop
>>> +	nop
>>> +	nop
>>
>> Why do you need this? Does the code get too long and enters  
>> exception handler space?
>>
> 
> Those are the reason I sent the patch as RFC: There seems to be some kind of
> alignment issue with the exception vectors. If the nops are not there, the
> board crashes as soon as the timer_interrupt is raised for the first  
> time.  The
> commit 96d2bb952bbf2e5a14f6ad668312cbce3cc4485a (powerpc/mpc85xx: Don't
> relocate exception vectors), among other things, removed the explicit  
> alignment
> of the vectors for E500. If you add those back in (and remove the nops), the
> code works too. So maybe some kind of alignment for the vectors is  
> needed after
> all?

There is requirement for alignment. For e500 core, the interrupt vector offset
registers (IVORs) have lowest 4 bit cleared. So the vectors must be aligned to
16 bytes. For legacy cores, the exception vectors are fixed. You have to make
sure the vectors are exactly where they should be.

I think you can use .align 4. Try it.

> 
>>> +#endif
>>>  	li	r0,0
>>>  	stw	r0,0(r3)	/* Terminate Back Chain */
>>>  	stw	r0,+4(r3)	/* NULL return address. */
>>> --
>>
>> This patch presumes stack is right under GD, which is OK. But
>> CONFIG_SYS_MALLOC_F_LEN has not been used by powerpc. Presumption of
>> (CONFIG_SYS_MALLOC_F_LEN + GENERATED_GBL_DATA_SIZE) <  
>> CONFIG_SYS_INIT_RAM_SIZE
>> may not be true. Would it be better to check at compiling time to  
>> make sure we
>> have enough init ram for the malloc len?
>>
> 
> Yes, good idea; I'll add an appropriate check in v2 of the patch. Maybe
> something like
> 
> #if CONFIG_SYS_MALLOC_F_LEN + GENERATED_GBL_DATA_SIZE + 0x80 >  
> CONFIG_SYS_INIT_RAM_SIZE
> #error "CONFIG_SYS_MALLOC_F_LEN too large to fit into initial RAM."
> #endif
> 
> to ensure we leave at least a minimum of ~128 byte stack space, too?
> 

I don't think so. We know the size of GD, and we know the size of MALLOC_LEN.
But we don't know the depth of stack until we compile it. I would put GD on top,
followed by MALLOC, and leave the rest to stack. I know the DDR driver we use
needs way more than 128 bytes for stack.

York