[linux-sunxi] Re: [PATCH 2/5] ARM: dts: sun4i: Add support for mmc

[Hans de Goede]

Hi,

On 12/16/2013 11:02 AM, Maxime Ripard wrote:
> Hi Hans,
>
> Damn google-groups removed me from Cc :)
>
> On Sun, Dec 15, 2013 at 03:31:29PM +0100, Hans de Goede wrote:
>>>> @@ -376,6 +385,13 @@
>>>>   				allwinner,drive = <0>;
>>>>   				allwinner,pull = <0>;
>>>>   			};
>>>> +
>>>> +			sdc0_pins_a: sdc0 at 0 {
>>>> +				allwinner,pins = "PF0","PF1","PF2","PF3","PF4","PF5";
>>>> +				allwinner,function = "mmc0";
>>>> +				allwinner,drive = <3>;
>>>> +				allwinner,pull = <1>;
>>>
>>> Wow, you need both the pullups and a 40mA output?
>>
>> Yes and no. The pullups are enabled by uboot and the allwinner
>> sources, most of my testing has been done without them, which
>> seems to work fine. I've enabled them to be consisten with the
>> allwinner sources and u-boot.
>
> Henrik was suggesting that in most boards it's not required to set up
> the internal pullups. Maybe we can just disable them by default, and
> we will always be able to enable them at the board level if needed.

Ok, I'm fine with disabling the pull-ups by default.

>> As for drive = <3>, we need drive = <2> for normal modes,
>> and drive = <3> for ddr mode. I simply picked <3> to keep
>> things KISS. It should not matter much in power usage, as
>> it will only make the flanks of the signal more steep. Once the
>> desired output level is reached the current will drop off. It will
>> use more current when changing the level, but for half the time,
>> so the effective power usage (current * time) is the same.
>
> Ok, let's keep it to 40mA then. It will indeed be simpler :)

Ack.

>
>>> Ideally, I'd like this patch to be splitted into three:
>>>    - One that adds the MMC controller nodes to the DTSI
>>>    - One that adds the muxing options you need to the pinctrl node
>>>    - One that enables the controller on the boards
>>
>> Sounds like a good job for David. Note I've a lot more boards for
>> which I would like to add mmc support or dts files in general
>> (will do so as time permits).
>>
>> For those boards which already have a dts I'll send mmc adding dts
>> patches to David for now so he can add the changes to the patch-set.
>>
>> How do you want to deal with new boards ? Send the addition of the
>> base board to you (and CC David as he will need them in his tree too),
>> and then send a patch to add mmc to the dts to David ?
>
> I don't really like having a variable-sweep patch serie. Just send
> your DT additions to me, saying that you depend on the MMC serie from
> David.

Ok will do if / when I've dts files for new boards.

Regards,

Hans