On Wed, 22 Sep 2021 20:24:18 +0200
Marek Vasut <ma...@denx.de> wrote:
On 9/22/21 7:29 PM, Marek Behún wrote:
(Adding also Tom.)
Hi Patrick, Marek,
I find this either not complete or not needed:
- either you need mtd names to be of this format so that old MTDPARTS
config definitions do not need to be changed, i.e. something like
CONFIG_MTDPARTS_DEFAULT="nor0:1M(u-boot),0x1000@0xfff000(env)"
does not work currently, and you want to make it work.
I find your solution here incomplete because MTDPARTS can also be
used to be passed to Linux as mtdparts parameter, but there is no
guarantee that the "norN" numbering you are creating in U-Boot will
be the same as the one in kernel.
- or it is not needed, because you can remove MTDPARTS definition from
the board config entirely and move the information into device tree.
In fact this was the main idea behind making the series
Support SPI NORs and OF partitions in `mtd list`
The SPI-NOR MTDs after this series can have conflicting names,
because you can still choose between them via OF path with the `mtd`
command.
Tom and I were of the opinion that MTDPARTS should be deprecated and
removed in favor of OF. Marek Vasut says that this is not possible
for every board, and so needs to stay.
BTW, I find it a little weird for Marek to defend old API which should
be converted to DT, when in discussion about DM USB / Nokia N900
USB TTY console [1] he was defending the opinion that we should be
heading to DT in U-Boot.
[1]
https://patchwork.ozlabs.org/project/uboot/patch/20210618145724.2558-1-p...@kernel.org/
That USB discussion is completely unrelated to the problem here, the USB
discussion is about internal (i.e. not user facing) conversion to DM/DT.
The user-facing ABI does not change there. Also, that discussion was
about patching USB stack to permit new non-DM/DT operation, not fixing
existing one.
This is not only about the user ABI (altough now I agree that you are
correct there, see below). What I meant is this:
Should we push for converting to device-tree even if for some boards
it is not possible, and would mean removing them?
Because you are saying that MTDPARTS cannot be converted to DT for
some boards.
But N900 also cannot be reasonably converted because of space
issues, as far as I understood. Yes, it has gigabytes of eMMC storage,
and it was proposed to put SPL in MTD and U-Boot proper into eMMC on
VFAT/ext4, but this simply cannot be done reasonably, because:
- it would break Linux userspace (existing OS upgrade system would
have to be rewritten and backwords compatibility would be broken)
- it would make bootstrapping (booting newer version of U-Boot) while
developing U-Boot a pain in the ass or maybe even impossible
- I beleive there was some other reason Pali mentioned, but I cannot
remember anymore
This problem here is user facing ABI, the mtdparts/mtdids. That user
facing ABI got broken. Boards which do depend on it, even those
currently in tree, are broken. Not all boards can update their
environment, so some backward compatibility of the user facing ABI
should be in place, even though it might not be to the degree Linux
kernel does so. So far, it seems most of the U-Boot command line
interface has managed to retain backward compatibility, I don't see why
this here should be handled any differently.
OK, I get that the if `mtd nor0` was working before, it should work also
now. But the conversion from MTDPARTS to device tree could be probably
done for lots of these, see below.
Note that there are not just a few boards that are broken, but hundreds.
I believe that itself justifies a fix, instead of just throwing all
those hundreds of boards overboard.
u-boot$ git grep -l CONFIG_MTDIDS configs | wc -l
203
Only 96 of those also grep the substring "nor". But okay, that is still
a lot. The question is how many of them could be rewritten to DT:
for cfg in $(git grep -l 'CONFIG_MTDIDS.*nor[0-9]' configs); do
fgrep CONFIG_DEFAULT_DEVICE_TREE "$cfg"
done | wc -l
92 of those 96 have CONFIG_DEFAULT_DEVICE_TREE defined.
Of these, 65 contain CONFIG_DM_SPI_FLASH=y, so at least these 65 could
be converted. Of the rest 27, how many could also be converted to DM?
How may use non-DM drivers?
