[RFC] Vocore2 MMC needs clock patches

[Weijie Gao]

On Tue, 2020-01-21 at 00:55 +0100, Mauro Condarelli wrote:
> Hi Weijie,
> I attach my, apparently working, port to VoCore2 SoM.
> 
> These patchsets are on top of Your 21 patch rewrite of MT7628 board,
> 
> While the first patchset is relatively straightforward, but does not include
> MMC handling, to enable it I had to backport from Linux Kernel several
> pieces, essentially clock and interrupt handling.

You are using a superseded patch series (v1) I submitted several months
ago. These patches have already been replaced by v3 and merged into the
mainline.

* "mtmips-clk-gate" from v1 is replaced by "mediatek,mt7628-clk" and the
  function of "mediatek,mt7628-clk" is a superset of "mtmips-clk-gate".
* The node "intc" has no use at all. U-Boot for mips use no interrupts.
* mmc property "hclk" is the gating clock of the SD controller module.
  Using <&clk48m> in the v1 patches was a bad idea. I changed it to
  <&clkctrl CLK_SDXC> in v3 to make sure its clock will be always
  enabled.
* Please move pinctrl properties to your board's dts file.
* pinctrl name "state_uhs" is not used by mtk-sd in U-Boot. MT7628 does
  not support UHS. You should remove it.
* vmmc-supply and vqmmc-supply are not used by mtk-sd in U-Boot because
  UHS support is not added to the driver. Besides you have assigned
  wrong values to them. You should remove it.

> 
> Those drivers appear written by You.
> I am unsure if this is really needed or if there is some other (perhaps
> cleaner)
> way to enable MMC.
> 
> As said this seems to work for me, but I would like to contribute this
> board upstream, in the best possible way.
> 
> Please let me know how I should proceed.

I don't have a board with the "sd_iot_mode" pinmux for SDXC, so I can't
tell you why you can't use it with my v3 patches. But I have tested v3
patches on boards using "sd_router_mode" pinmux and they do work well.

> 
> Best Regards and Thanks in Advance
> 
>