[linux-sunxi] Re: [PATCH 4/5] ARM: dts: sun5i: Add dts file for the Empire Electronix D709 tablet

Hans de Goede
2015-12-21T19:36:53Z

Hi,

On 21-12-15 17:11, Maxime Ripard wrote:
> Hi,x
>
> On Mon, Dec 21, 2015 at 11:46:18AM +0100, Hans de Goede wrote:
>>> On the side, any thoughts on how to handle the differences between various "Q8"
>>> tablets, like different I2C-based sensors and WiFi chips?
>>
>> For i2c based sensors the plan is to use devicetree overlays + an in kernel
>> overlay manager which probes the i2c bus (checking known touchscreen / accelerometer
>> addresses) and then picks the right touchscreen + accelerometer overlays.
>>
>> Wifi is somewhat more tricky I must admit, esp. since there seem to be q8 a23 based
>> tablet variants with usb wifi and others with sdio wifi. Since both busses are
>> discoverable I'm tempted to just enable both in devicetree, and let the kernel probe
>> and see what is actually there. This assume that the way the wifichip is powered
>> is the same on all boards, or at least that it is safe to enable the necessary
>> regulators on all boards ...
>>
>>> I'm asking because with Maxime's couple-regulator we should be able to get the
>>> RTL8723BS on the Q8 A23/33 v1.5 working.
>>
>> So this means enabled the sdio controller (should be safe on all boards?) and
>> enabling 2 regulators to power the wifi-chip. I think it will be safe to do this
>> even on boards where those regulators are not used, what do you think ?
>
> Wouldn't that introduce some useless power drain on those boards?

If nothing is attached to those regulators (which I expect to be the case when
they are not used to power wifi) then I would expect the drain to be minimal,
my biggest worry is some board having tied these to ground, but I don't think
that is very likely.

Regards,

Hans