On 29/11/18 4:48 PM, Simon Goldschmidt wrote:
On Thu, Nov 29, 2018 at 11:56 AM Miquel Raynal miquel.raynal@bootlin.com wrote:
Hi Vignesh,
While I think porting this from Linux is the right thing to do, I can't say I'm happy with losing yet another 2.5 kB for SPL when it is already too stuffed to add secure boot via FIT signatures.
Indeed. Can we somehow trim things down a bit for SPL ?
I am able to trim overall size delta to within 1KB for porter_defconfig. Pushed new set of patches to github[1]
With new this new SF framework and porter_defconfig: size spl/u-boot-spl text data bss dec hex filename 15749 184 1100 17033 4289 spl/u-boot-spl
Current mainline: size spl/u-boot-spl text data bss dec hex filename 14881 184 1100 16165 3f25 spl/u-boot-spl
Typical increase in code delta is ~1K to ~1.2KB wrt SPL on different platforms depending on flash devices supports enabled.
I am not sure if its possible to trim this down further, as there is addition of new code to handle 4 Byte addressing feature and moving to spi-mem framework to support direct mapping capable SPI controllers. These features will add to code size and I hope that's an acceptable tradeoff.
I believe, once SPI NOR is completely integrated with MTD framework, there will be some size reduction(such as due to getting rid of sf_mtd.c and spi_flash_* APIs completely. Also, loading of U-Boot images across NAND/SPI NOR can be consolidated).
There are already multiple SPL-specific drivers out there. While I don't see a problem building MTD in U-Boot, I wonder if building MTD in the SPL is a good idea. Instead, Why not just build a tiny "SPL MTD stack", a lightweight MTD stack just with minimal features?
I think that would be a good idea. Simple read access should probably be enough for SPL to load U-Boot. That would free some space I need to verify FIT signatures...
Okay, I plan to implement spi-nor-tiny.c as part of next version that would support just discovering connected flash via JEDEC ID and reading images from flash at best possible IO mode with 4-byte addressing. This can serve as lightweight SPL stack for SPI NOR to overcome size limitations. Let me know if there are any concerns.
Thanks for the suggestions!