[U-Boot] [PATCH 00/25] sunxi: Enable DM_MMC for U-Boot proper

[Andre Przywara]

Hi,

On 16/07/18 10:52, Maxime Ripard wrote:
> On Mon, Jul 16, 2018 at 04:35:09PM +0800, Chen-Yu Tsai wrote:
>> On Mon, Jul 16, 2018 at 4:19 PM, Jagan Teki <jagan at amarulasolutions.com> wrote:
>>> Enabling DM_MMC is not straight forward for Allwinner SoC's to
>>> make proper compatibility in mmc driver vs DT nodes.
>>>
>>> Existing dm code for ahb gate clock will be suitable to handle
>>> sun4i,5i,6i and 7i U-Boot specific mmc dt nodes, which are different
>>> from Linux in terms of clocks phandle notation.
>>>
>>> U-Boot DT clocks phandle follow direct ahb and clock address on
>>> node definition with specific bit position, but Linux clocks phandle
>>> follow macros to define AHB and MMC clocks so-that the ccu driver
>>> will set the bits accordingly.
>>
>> And that has been deprecated upstream.
>>
>>> Clocks phandle notations in U-Boot for higher Allwinner SoC start
>>> from sun8i, sun50i are following Linux notation so-that both Linux
>>> and U-Boot can have common node definition.
>>
>> So basically you're saying the additional code for clock/reset
>> handling through the device tree only works for half of the SoCs,
>> based on a deprecated device tree binding. Which means we're
>> going to throw it out some time in the future. Is it worth the
>> churn of driver and device tree changes?
>>
>> IMHO the new clock handling code is no better than the old. The only
>> thing that has changed is how the clock register address is derived.
>> Not even the index numbers, which BTW are actual bit offsets, for
>> the AHB gates from the device tree are used. Neither is the device
>> tree used for the AHB resets.
> 
> I'd say that it's even worse. We want an actual, common, clock
> driver. Not a quick hack that doesn't solve any of the issues we're
> facing.

So is the purpose of this whole series to just comply with the
deprecation of non-DM_MMC configurations?
As mentioned before I am wondering how useful this is, and if we could
ever get rid of those hardcoded hacks for the SPL anyway (so the driver
would technically be DM_MMC compliant, but still had non-DM_MMC code in).
So I would suggest we push the clock DM driver forward first [1],
implementing the new CCU binding, then possibly convert over the pre-H3
boards.
And meanwhile we try to appease the maintainers to not remove any boards
which don't support DM_MMC, because the purpose of U-Boot should be to
get boards booting and not to have some fancy driver model just for the
sake of it.

Cheers,
Andre.

[1] https://github.com/apritzel/u-boot/commits/sunxi-dm-WIP