[U-Boot] [PATCH v2 2/2] Tegra: MMC: Add DT support to MMC driver for all T20 boards

[Tom Warren]

Lucas,

On Tue, Feb 12, 2013 at 12:41 PM, Lucas Stach <dev at lynxeye.de> wrote:
> Hello Tom,
>
> Am Dienstag, den 12.02.2013, 12:24 -0700 schrieb Tom Warren:
>> Lucas,
>
>> >>>
>> >> tegra_mmc_init should not be called from every individual board file,
>> >> but from the common nvidia tegra board file. Only the pinmux should stay
>> >> in the individual board code, same thing as was done to all the other
>> >> functions like NAND and USB.
>> >
>> > True. I was originally just adapting the current config-file driven
>> > MMC to DT step-by-step, but you're right - it should be called just
>> > once for all boards in the common board file. I'll change it in V3.
>>
>> I've looked into this some more, and it appears that I can't just add
>> a call to tegra_mmc_init() from board_init() in
>> boards/nvidia/common/board.c.
>>
>> board_init() is where the other periphs do their pin_mux and
>> xxx_init() calls (USB, SPI, etc.).  board_init() is called early in
>> board_init_r(), before mmc_initialize() is called. mmc_initialize() is
>> needed before tegra_mmc_init() can use the mmc_device struct, etc. So
>> tegra_mmc_init() needs to be called after mmc_initialize(), and right
>> now that's in each board's board_mmc_init().  In board_mmc_init(),
>> each board sets up any power rails needed for SD-card or eMMC access,
>> sets up it's pin muxes for MMC, and then calls tegra_mmc_init() to
>> parse the DT file and populate the mmc structs.
>>
>> I could move the pin_mux_mmc() function calls from each board file
>> into nvidia/common/board.c's board_init(), but it wouldn't really
>> change much. So I'll leave it as it is for now, with pin_mux_mmc() and
>> tegra_mmc_init() being called from each board's 'board' file
>> (seaboard.c, colibri_t20_iris.c, etc).
>>
>> Let me know if you see another way to move Tegra MMC init to a common
>> board file that doesn't break the MMC driver flow.
>>
>
> I didn't look up the flow myself, as I don't have time for that right
> now, but I think I've got a pretty good picture from your description.
Thanks for the quick response.

>
> I think we should really try to make the Tegra MMC init flow as similar
> as possible to the other peripherals, so I suggest doing the following:
> 1. Provide a pin_mux_mmc() (possibly with a weak define as done with
> other peripherals). Boards should do pinmux and rail enabling within
> this function.
(Almost) every Tegra board already has a pin_mux_mmc(). Few boards do
any power-rail enabling, but I can move those that do into
pin_mux_mmc().

> 2. Move board_mmc_init() into nvidia/common/board.c, this function
> should call into the board specific pinmux function and then call
> tegra_mmc_init().
Current board_mmc_init() does call pin_mux_mmc() and then
tegra_mmc_init(). Moving it from each board file into common/board.c
is a good idea. I'll try that.

Thanks
>
> So even while we don't get the complete same flow as for other
> peripherals as the board_mmc_init() still has to be a freestanding
> function, instead of those things being folded into board_init(), we at
> least gain a clear distinction between the board specific parts and
> Tegra common code.
>
> Regards,
> Lucas
>