U-Boot sunxi DM_I2C migration?

[Tom Rini]

On Wed, Aug 18, 2021 at 12:20:10AM -0500, Samuel Holland wrote:
> Hi all,
> 
> On 8/17/21 2:23 PM, Tom Rini wrote:
> > On Thu, Aug 12, 2021 at 05:40:34PM -0400, Tom Rini wrote:
> >> On Thu, Aug 12, 2021 at 10:22:07PM +0100, Andre Przywara wrote:
> >>> On Thu, 12 Aug 2021 13:49:30 -0400
> >>> Tom Rini <trini at konsulko.com> wrote:
> >>>
> >>> Hi Tom,
> >>>
> >>>> As I try and migrate more CONFIG symbols to be Kconfig only, I see that
> >>>> sunxi is still using the legacy I2C drivers.  Is there something
> >>>> specific holding up migration?  Thanks!
> >>>
> >>> Do you mean a DM_I2C conversion, or just moving those base address
> >>> symbols to Kconfig? The latter is rather easy, let me know if I should
> >>> give it a shot.
> >>>
> >>> For DM_I2C, it's the usual sunxi issue: we are using both: DM_I2C and
> >>> DT based probing for U-Boot proper, and hardcoded CONFIG_ symbols for
> >>> the SPL. *Some* boards need the set up the PMIC early (for increasing
> >>> the CPU frequency or setting the proper DRAM voltage), so this needs to
> >>> be done in the SPL. I don't know how to fix this "properly",
> >>> but introducing DM (and DT) into the SPL is surely not worth the
> >>> trouble. Alternatively we could have a separate, cut-down SPL-only
> >>> driver, like we have for SPI (arch/arm/mach-sunxi/spl_spi_sunxi.c),
> >>> but not sure that's really better.
> >>>
> >>> If there is something in particular that annoys you about the
> >>> situation, we could try to improve this particular issue instead?
> >>> Moving the non-DM code into a separate file, maybe?
> >>
> >> I'm working on the symbols now (since it gets tricky).  The first
> >> example I pulled out was Hummingbird_A31 which does have legacy I2C and
> >> does not set DM_I2C, which is what set me down the more worrying path.
> >> If you can confirm that no, really, it's just SPL that's not using
> >> DM_I2C that's OK enough for now, we can sort out what the best but
> >> probably still unideal solution is long term for SPL.
> > 
> > As I'm converting the symbols to Kconfig now (and adding
> > SPL_SYS_I2C_LEGACY), what I'm seeing on sunxi is a whole lot of platform
> > enabling the legacy driver in full U-Boot and not DM_I2C.  Now it's
> > entirely possible the follow up solution really is just to switch to
> > DM_I2C (and continue SPL_SYS_I2C_LEGACY) and it would be a fairly
> > trivial switch.  But I'm not in a good position to make that change and
> > test it, so I'm asking you to please, once I've posted this series to
> > add SPL_SYS_I2C_LEGACY
> 
> I am aware of three places where sunxi boards use legacy I2C in U-Boot proper:
>  - The i2c_soft usage enabled by CONFIG_VIDEO_LCD_PANEL_I2C
>  - The axp_gpio driver (through pmic_bus_*)
>  - do_poweroff() in drivers/power/axp*.c (through pmic_bus_write)
> 
> I have a patch series for converting all of these that I will be sending within
> the next few days. The two tricky parts are:
>  - I have no way to test either board that uses VIDEO_LCD_PANEL_I2C,
>    so I do not want to rely on bus number ordering.
>  - I am trying to arrange changes in an order that never breaks any
>    functionality, so some driver must be temporarily compatible with
>    both legacy and DM I2C.
> 
> I will rebase this on top of the Kconfig series before sending it.

Great, thanks!

-- 
Tom
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