On Monday, February 18, 2013 7:02:49 PM, Scott Wood wrote:
On 02/18/2013 12:00:52 PM, Benoît Thébaudeau wrote:
On Monday, February 18, 2013 6:27:50 PM, Tom Rini wrote:
Commit 74752ba performs a '--pad-to=$(or $(CONFIG_SPL_PAD_TO),0)' on u-boot-spl. I could use this CONFIG_SPL_PAD_TO for this series too, but is it really necessary to have both CONFIG_SPL_PAD_TO and CONFIG_SPL_MAX_SIZE? In other words, is there any case for which CONFIG_SPL_PAD_TO could be different from CONFIG_SPL_TEXT_BASE + CONFIG_SPL_MAX_SIZE for a valid reason?
They're logically different things.
I was wondering along those lines. I don't _think_ we need both CONFIG_SPL_PAD_TO and CONFIG_SPL_MAX_SIZE, but we can't combine CONFIG_SPL_MAX_SIZE and CONFIG_SPL_TEXT_BASE as on TI platforms we start quite well above zero (0x402F0400 on am33xx, etc). That
said, I
guess we do need CONFIG_SPL_PAD_TO so that some platforms can do: #define CONFIG_SPL_PAD_TO (CONFIG_SPL_TEXT_BASE +
CONFIG_SPL_MAX_SIZE)
and others just #define CONFIG_SPL_PAD_TO CONFIG_SPL_MAX_SIZE
If we did like my patch here, i.e. use objcopy with u-boot-spl.bin instead of u-boot-spl, objcopy would always get a fake 0x0 address at the beginning of the .bin, so CONFIG_SPL_MAX_SIZE could be used with --pad-to, and CONFIG_SPL_PAD_TO would be useless.
The only question is if we may need to have an empty gap between the SPL and U-Boot within the resulting image. I don't think so since that would mean that the target memory device has an area that is not really available at the location of this gap.
Why not allow that possibility?
To save a config setting (there are already many for SPL) if this is not strictly required, but also for the reason below.
Maybe it's easier for the SPL to load from a particular offset (e.g. NAND starting at the beginning of a block)?
CONFIG_SPL_MAX_SIZE would be closer to a NAND mapping in that case (e.g. size of 1 NAND Flash block) than CONFIG_SPL_PAD_TO (address within RAM that should be considered relatively to CONFIG_SPL_TEXT_BASE to get the NAND offset).
Also, CONFIG_SPL_PAD_TO and CONFIG_SPL_MAX_SIZE depend on each other: If both can be defined, you may change one forgetting the other one, which could e.g. result in an overlapping of SPL and U-Boot that won't show up at build time (with CONFIG_SPL_MAX_SIZE = 0x1000 and CONFIG_SPL_PAD_TO = CONFIG_SPL_TEXT_BASE + 0x800, the SPL would build fine, and objcopy wouldn't complain).
Best regards, Benoît