[U-Boot] [PATCH] ARM: keystone: Pass SPI MTD partition table via kernel command line

[Tom Rini]

On Tue, Mar 14, 2017 at 05:11:06PM +0530, Vignesh R wrote:
> [...]
> 
> On Friday 10 March 2017 11:32 PM, Tom Rini wrote:
> >> Yes, I agree that initial DT layout of 512K may not have been good
> >> design, but it would be good to have an agreeable way of fixing up MTD
> >> partitions when there is overflow. So, is fdt_fixup_mtdparts() preferred
> >> approach?
> > You make a good point about fdt_fixup_mtdparts() being non-trivial to
> > have happen correctly in all cases above, so OK, lets put that aside.
> > I'll also accept that previous best wisdom of not shoving tons of stuff
> > into the cmdline, rather than passing it in the device tree, isn't
> > correct anymore.
> > 
> > But the big, un-tackled problem is that the old DT layout is failing
> > because we're constantly increasing the number of full linux DTB files
> > we're including in an image and thus increasing the size of our blob
> > every time.  We need to stop and think and maybe design things
> > differently.  Perhaps it's time for more platforms to have a spot on
> > their storage where the DT is supposed to be, and we only use a fall
> > back one that's included in U-Boot if it's not found?  Franklin already
> > posted a patch to have something kind-of similar be able to happen
> > (which is to say, go from a generic DTB to the correct-for-the-HW one).
> 
> I agree that DTB files are making u-boot image bulky. But it does not
> seem to be problem due to addition of DT alone. For example SPI boot
> image on K2 platform is two stage SPL+U-Boot combined into one single
> image u-boot-spi.gph which is about 555K. General boot image u-boot.bin
> is about 491K and u-boot-nodtb.bin is 432K. So even w/o dtbs SPI image
> may overflow and its because of new code/framework changes.

Which platform exactly?  I don't see anything today that's quite that
large.  And can we not move towards the "normal" method of SPL loading
the u-boot.img (or FIT) from?  I guess the current architecture here is
confusing me.

Regardless, I still see the DT problem as the bigger one long term, and
dra7xx shows that.  And I agree we need to re-size how the flash is
partitioned.

> There is similar issue with dra7xx where flash partition for SPL is
> running out due to addition of new code.

The DRA flash partition is, and should be fine because we have the
ROM-mandated limits and don't need to include U-Boot with the SPL image.
The main U-Boot image however is growing and that is a DTB problem.  The
difference here between -nodtb and the .img (FIT) with all of the DTBs
is over 300KiB.  And that's mostly linear growth when compared with the
single-DTB case.

-- 
Tom
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