[U-Boot] [PATCH 1/3] powerpc/p1010rdb: SECURE BOOT- define CONFIG_SYS_RAMBOOT for NAND boot

[York Sun <yorksun@freescale.com>]

On 03/07/2014 10:57 AM, Scott Wood wrote:
> On Thu, 2014-03-06 at 03:24 -0600, Bansal Aneesh-B39320 wrote:
>>> -----Original Message-----
>>> From: Wood Scott-B07421
>>> Sent: Wednesday, March 05, 2014 11:30 PM
>>> To: Bansal Aneesh-B39320
>>> Cc: Sun York-R58495; Wolfgang Denk; u-boot at lists.denx.de; Gupta
>>> Ruchika-R66431
>>> Subject: Re: [U-Boot] [PATCH 1/3] powerpc/p1010rdb: SECURE BOOT-
>>> define CONFIG_SYS_RAMBOOT for NAND boot
>>>
>>> On Tue, 2014-03-04 at 23:30 -0600, Bansal Aneesh-B39320 wrote:
>>>> Yes, in case of secure boot from NAND, the DRAM is initialized by
>>> the
>>>> BootROM and complete u-boot image is copied from NAND to DRAM by the
>>> BootROM.
>>>> So, it should be called RAMBOOT.
>>>
>>> DRAM or SRAM?  Having ROM initialize DDR is a bit scary.
>>>
>>> -Scott
>>>
>> It can be either DDR or SRAM. It is not hardcoded in BootROM to initialize DDR.
>> This depends on the config words (CF_WORDS) in the CF_HEADER.
>> The Boot ROM code parses the config words and programs the addresses with data values
>> accordingly. The user may opt to initialize DDR and get the image copied onto DDR or 
>> configure CPC as SRAM and get the Image copied onto SRAM.
>> On 1010,
> 
> P1010?  LS1010?  Something else?
> 
>> the CPC size is not big enough to accommodate the U-boot image.
>> So, currently the CF_WORDS are for DDR to be initialized and copy the image on DDR.
> 
> Generally if SPD is present, it should be used to init DDR rather than
> using hardcoded values.  If U-Boot doesn't fit in SRAM, you can use SPL
> instead of hardcoded init.

I agree with Scott on this point. Using hardcoded values totally skip DDR
driver. You don't only lose the flexibility of various speeds, you also skip all
workarounds implemented in DDR driver.

York