[U-Boot] [PATCH 66/93] arm: Remove ot1200 board

Wed Dec 5 13:21:07 UTC 2018

Hi Simon,

On Sun, 25 Nov 2018 at 23:05, Simon Goldschmidt
<simon.k.r.goldschmidt at gmail.com> wrote:
>
> [I've cut down the CC list a bit due to some gmail warnings]
> On Mon, Nov 26, 2018 at 4:00 AM Simon Glass <sjg at chromium.org> wrote:
> >
> > Hi Simon,
> >
> > On Sun, 25 Nov 2018 at 14:09, Simon Goldschmidt
> > <simon.k.r.goldschmidt at gmail.com> wrote:
> > >
> > > On Thu, Nov 22, 2018 at 9:50 PM Simon Glass <sjg at chromium.org> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On Thu, 22 Nov 2018 at 10:02, Tom Rini <trini at konsulko.com> wrote:
> > > > >
> > > > > On Thu, Nov 22, 2018 at 03:44:28PM +0100, Simon Goldschmidt wrote:
> > > > > > Am Do., 22. Nov. 2018, 14:44 hat Tom Rini <trini at konsulko.com> geschrieben:
> > > > > >
> > > > > > > On Thu, Nov 22, 2018 at 02:24:49PM +0100, Marek Vasut wrote:
> > > > > > > > On 11/22/2018 01:52 PM, Tom Rini wrote:
> > > > > > > > > On Thu, Nov 22, 2018 at 10:25:14AM +0100, Christian Gmeiner wrote:
> > > > > > > > >
> > > > > > > > >> Am Mo., 19. Nov. 2018 um 16:56 Uhr schrieb Simon Glass <
> > > > > > > sjg at chromium.org>:
> > > > > > > > >>>
> > > > > > > > >>> This board has not been converted to CONFIG_DM_BLK by the deadline.
> > > > > > > > >>> Remove it.
> > > > > > > > >>>
> > > > > > > > >>
> > > > > > > > >> As the board is still mainted I will NAK it for the moment. Are there
> > > > > > > > >> any hints want needs to be done
> > > > > > > > >> to port thie board over to new DM stuff?
> > > > > > > > >
> > > > > > > > > Yes, as a start you need to switch over to using CONFIG_OF_CONTROL and
> > > > > > > > > selecting/providing a dtb file.  I see ot1200 is using DWC_AHSATA which
> > > > > > > > > needs more work, but this is the board-level work that needs doing.
> > > > > > > >
> > > > > > > > Wasn't there a possibility to use platform data in board file instead of
> > > > > > > > DT ? Or is DT mandatory now , including the libfdt overhead ?
> > > > > > >
> > > > > > > In short, DT for U-Boot and platform data for SPL is what's recommended,
> > > > > > > yes.
> > > > > > >
> > > > > >
> > > > > > This is a little confusing for me. Socfpga gen5 SPL doesn't do that. And it
> > > > > > seems a little strange or outdated overall.
> > > > > >
> > > > > > Would there be some kind of reference architecture or mach to look at
> > > > > > what's the suggested/up-to-date way to implement SPL? Also regarding code
> > > > > > flow?
> > > > >
> > > > > So, SPL is where things get, ahem, fuzzy.  While I don't want to
> > > > > encourage boundless growth in U-Boot proper, we aren't exactly size
> > > > > constrained (but rather, functional/logical constrained).  But in SPL,
> > > > > yes, we have many platforms with 32/64/128 kilobyte hard limits (and
> > > > > some smaller) and we can't always shove in a "TPL" before SPL either.
> > > > > So in SPL we do make use of platform data instead.  While not the
> > > > > smallest size constraint, am335x_hs_evm is a reasonable thing to look at
> > > > > in this case.
> > > >
> > > > Also 'rock' uses CONFIG_OF_PLATDATA which provides a halfway house -
> > > > still uses DT, but it gets converted into C structs so saves code
> > > > space.
> > > >
> > > > firefly-rk3288 is a pretty good DM/DT example, including SPL.
> > >
> > > I've currently got an issue on socfpga gen5 that could be solved best
> > > by enabling CONFIG_OF_EMBED (mixing const and non-const sections is a
> > > problem for CRC calculation). However, it could probably also solve by
> > > using platform data (but that doesn't work out of the box, yet). The
> > > problem with CONFIG_OF_EMBED is that I think it's OK to enable this
> > > for SPL but I don't like enabling it for U-Boot, so:
> > >
> > > Would it make sense to duplicate the whole "Provider of DTB for OF
> > > control" choice so that it can be OF_EMBED for SPL but different for
> > > U-Boot? Or does it make more sense to convert socfpga gen5 to use
> > > OF_PLATDATA?
> >
> > We should not be using OF_EMBED in in-tree boards or production code.
>
> What's the reason for this? I can understand this for U-Boot, and I
> can understand that it's at least theoretically a bit cleaner for SPL,
> too. But there are some drawbacks when doing this in SPL where code is
> not relocated:
> - you lose the ability to check total size in linker file (which is
> bad for size-constrained platforms: sometimes you notice failure only
> when booting)

You can add an SPL size check in Makefile.spl if you like.

> - you get an inconsistent memory layout regarding read/write: the
> linker places bss at the end but then, DTB follows as const data

This should be handled by the $(SPL-BIN)-pad.bin file (or by binman if
you are using that).

> - binary size "on disk" grows due to this inconsistent memory layout
> (since the flat binary includes the DTB, it needs to include the
> zeroed-out bss, too)

Right, but this is a few bytes. Why does it matter?

> - "spl/u-boot-spl.hex" created by the default Makefiles does not seem
> to include the DTB

That might just be a bug.

>
> > Can you please explain the issue a bit more?
>
> Of course: socfpga gen5 has a feature where the boot rom can jump to
> SPL in SRAM on warm boot. To ensure SPL is still valid after a reboot,
> the boot rom can check its consistency by calculating a CRC over one
> specified range in SRAM. On first boot, SPL stores its start, length
> and CRC value to special registers for the boot rom. Since the
> contents of bss changes while SPL is running, bss cannot be included
> in this CRC range. (Same goes for the '.data' region, but it's
> possible to build SPL without actually using it.)

How about calculating that checksum at build time instead? You could
use binman to do that.

>
> So to ensure the DTB is untouched, I have to make sure it has a lower
> address than the bss section. Using OF_EMBED does this for me. And I
> expect using platform data would work too. Do you have another idea
> how to achieve my goal of combining all write-only sections in SPL
> into one block?

Yes, do it at build time. Or calculate your CRC before you write any
BSS variables.

>
> Oh, and I currently count 109 defconfig files containing "OF_EMBED",
> so I wasn't aware that this should not be used. Maybe these platforms
> have similar reasons like I have and would enable OF_EMBED only for
> SPL if they could. At least for socfpga_stratix10 that should work.

That is very bad news. I'll see about adding a Makefile warning.

Regards,
Simon