From mboxrd@z Thu Jan 1 00:00:00 1970 From: hdegoede@redhat.com (Hans de Goede) Date: Mon, 21 Dec 2015 20:36:53 +0100 Subject: [linux-sunxi] Re: [PATCH 4/5] ARM: dts: sun5i: Add dts file for the Empire Electronix D709 tablet In-Reply-To: <20151221161132.GA30359@lukather> References: <1450611782-9494-1-git-send-email-hdegoede@redhat.com> <1450611782-9494-4-git-send-email-hdegoede@redhat.com> <5677D87A.90805@redhat.com> <20151221161132.GA30359@lukather> Message-ID: <567854D5.7030601@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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