[U-Boot] SPL Platdata howto?

[Simon Glass]

Hi Simon,

On Fri, 4 Jan 2019 at 00:15, Simon Goldschmidt
<simon.k.r.goldschmidt at gmail.com> wrote:
>
> On Fri, Dec 21, 2018 at 10:20 PM Simon Goldschmidt
> <simon.k.r.goldschmidt at gmail.com> wrote:
> >
> >
> >
> > Am Fr., 21. Dez. 2018, 22:16 hat Simon Glass <sjg at chromium.org> geschrieben:
> >>
> >> Hi Simon,
> >>
> >> On Thu, 20 Dec 2018 at 14:32, Simon Goldschmidt
> >> <simon.k.r.goldschmidt at gmail.com> wrote:
> >> >
> >> > Am 20.12.2018 um 21:53 schrieb Simon Goldschmidt:
> >> > > Am 20.12.2018 um 18:37 schrieb Simon Glass:
> >> > >> Hi Simon,
> >> > >>
> >> > >> On Thu, 20 Dec 2018 at 08:03, Simon Goldschmidt
> >> > >> <simon.k.r.goldschmidt at gmail.com> wrote:
> >> > >>>
> >> > >>> Am 20.12.2018 um 15:49 schrieb Simon Glass:
> >> > >>>> Hi Simon,
> >> > >>>>
> >> > >>>> On Wed, 19 Dec 2018 at 14:06, Simon Goldschmidt
> >> > >>>> <simon.k.r.goldschmidt at gmail.com> wrote:
> >> > >>>>>
> >> > >>>>> Hi,
> >> > >>>>>
> >> > >>>>> while searching for bytes to save in SPL in order to add FIT signature
> >> > >>>>> handling, I am currently trying to get socfpga-gen5 to use OF_PLATDATA.
> >> > >>>>>
> >> > >>>>> To begin, I stripped down socfpga_socrates_defconfig to absolutely
> >> > >>>>> nothing but serial drivers in SPL (with some modifications to the
> >> > >>>>> Kconfig) and enabled DEBUG_UART to see what's going on.
> >> > >>>>>
> >> > >>>>> Now while this config runs OK with a dtb (it just won't boot as drivers
> >> > >>>>> are missing -> "failed to boot from all boot devices"), it does not find
> >> > >>>>> the serial driver after enabling OF_PLATDATA.
> >> > >>>>>
> >> > >>>>> So since serial_rockchip.c already uses OF_PLATDATA and is based on
> >> > >>>>> ns16550 that my socfpga-gen5 platform is using: what do I have to do
> >> > >>>>> besides enabling OF_PLATDATA to get this working?
> >> > >>>>>
> >> > >>>>> I just seems like uclass_first_device does not find any UCLASS_SERIAL
> >> > >>>>> deivce when OF_PLATDATA is enabled.
> >> > >>>>
> >> > >>>> There is the of-plat.txt README.
> >> > >>>
> >> > >>> Yes, I should have mentioned I already read that and still had those
> >> > >>> questions. Kconfig help says README.platdata though. We probably should
> >> > >>> update that link.
> >> > >>>
> >> > >>>> Basically the dtoc tool creates U_BOOT_DEVICE() declarations and links
> >> > >>>> them with SPL. These should show up in your image and therefore be
> >> > >>>> bound. You can call dm_dump_all() in SPL to see what what devices are
> >> > >>>> bound. I presume you are calling spl_init()?
> >> > >>>>
> >> > >>>> You can look at what dtoc produces. The example serial driver for
> >> > >>>> Rockchip is serial_rockchip.c
> >> > >>>
> >> > >>> I saw that as an example (because I also have an ns16550 compatible on
> >> > >>> my board) but couldn't figure out why it is not bound. By debugging
> >> > >>> 'dm_scan_platdata', 'lists_bind_drivers' and 'device_bind_by_name', by
> >> > >>> now I know the driver names don't match. That is something I did not get
> >> > >>> just by reading of-plat.txt. I'll work on a patch to clarify that document.
> >> > >>
> >> > >> Yes I'd really appreciate some patches here. It is hard to know what
> >> > >> people won't understand and this feature could really do with a more
> >> > >> details docs or a walk-through.
> >> > >>
> >> > >>>
> >> > >>> Right now, serial works. I had to add a new platform specific driver
> >> > >>> just like serial_rockchip though. For DTS, we can pass multiple
> >> > >>> 'compatible' strings, but for platdata, we have to create multiple
> >> > >>> drivers. That's a bit strange when porting boards...
> >> > >>
> >> > >> Yes it is. I'm not sure how to solve that though. Probably dtoc can be
> >> > >> made smarter. Ideally you only need one device of each uclass in SPL.
> >> > >
> >> > > Would it work to use the unchanged 'compatible' string for the '.name'
> >> > > of U_BOOT_DEVICE generated by dtoc? Then the binding of such drivers
> >> > > could change from comparing names to comparing to compatibles. That
> >> > > would make it more DTS-like.
> >> > >
> >> > > Then, I think we could need some kind of fallback code for properties
> >> > > that are optional in the DTS. Maybe we can create defines for each dtd
> >> > > struct so that drivers can test the existence of dtd sturct fields using
> >> > > #ifdef. [Given the special usage, I guess it's OK to assume that theses
> >> > > structs are only used once per DTS so that we don't have to worry about
> >> > > how to solve this for multiple occurrences with different optional
> >> > > parameters?]
> >> > >
> >> > > Oh, and then I think dtb_platdata.py should create the dtd instances as
> >> > > const. I'll prepare a patch for that.
> >> > >
> >> > >>
> >> > >>>
> >> > >>>>
> >> > >>>>>
> >> > >>>>> (And when answering this, keep in mind I need to get MMC and QSPI
> >> > >>>>> drivers working with OF_PLATDATA - I already fixed compiler errors in
> >> > >>>>> those, nothing more.)
> >> > >>>>
> >> > >>>> Yes MMC should be OK, but QSPI might be blazing a bit of a trail.
> >> >
> >> > Hmm, QSPI works as well when hacking the things that the driver wants to
> >> > parse from subnode properties. However, I haven't found a way to access
> >> > the platform data of the spi-flash from the driver.
> >> >
> >> > Maybe we need to somehow make subnodes available in the dt-platdata
> >> > structs to make that work?
> >>
> >> There is support for phandles but not for parent relationships. I
> >> suppose it would not be impossible to add that in dtoc with a 'parent'
> >> pointer.
> >
> >
> > SPI flash actually needs it the other way round. At least the cadence qspi driver I'm using checks for a subnode that describes the flash chip.
> >
> > I'll see if I can add that to dtoc.
>
> By now I have SPI successfully running with platdata by adding child
> arrays to the platdata struct via dtoc.
>
> However, probing the flash chip is not found in 'spi_get_bus_and_cs'
> and so the transfer falls back to 100 kHz, which is of course bad.
> That code expects a udevice child under the spi udevice. Looks like
> that needs more changes than just in dtoc?
>
> Did you have SPI running with platdata on any board, yet?

No. The implementation does not deal well with parent/child
relationships, as with buses, and in every case we need to make
changes.

That said, spi_get_bus_and_cs() is only used if you don't have the SPI
device in the DT.

Regards,
Simon