From mboxrd@z Thu Jan 1 00:00:00 1970 From: icenowy@aosc.io (Icenowy Zheng) Date: Tue, 07 Nov 2017 16:20:43 +0800 Subject: AXP803 I2C support / AXP devicetree-bindings In-Reply-To: References: Message-ID: <2bcdd4c97a13b1c24eccdf6f7d73e00b@aosc.io> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org ? 2017?11?7? GMT+08:00 ??11:13:23, Chen-Yu Tsai ??: > On Tue, Nov 7, 2017 at 6:39 AM, Martin Blumenstingl > wrote: >> Hello, >> >> recently I discovered that there are some X-Powers AXP chips that >> support both, Allwinner's own "RSB" as well as the I2C ("TWSI" in the >> datasheet) busses. >> >> one chip that supports both interfaces is the AXP803 >> the datasheet is linked in the public PINE64 wiki: [1] (direct link: > [0]) > > All the RSB based PMICs support both modes. They start in I2C mode > when cold booted. I think it starts at a vendor-customized mode. In all PMICs sold with Allwinner SoCs the mode is predefined to RSB. In fact many registers in AXPs are vendor-customizable, see the datasheets. > >> >> currently the "x-powers,axp803" binding is "RSB" bus specific as it's >> currently only listed in drivers/mfd/axp20x-rsb.c >> >> was there a discussion about supporting both, the "RSB" and I2C bus >> for one chip (for example the AXP803) in the past (I couldn't find >> anything online)? > > No. None of the boards actually use I2C instead of RSB. RSB mode is > initialized by the boot loader. There is no easy way for the kernel to > switch it back. > >> what about the device-tree bindings in this case? > > We can deal with it if someone actually comes up with a practical > case needing it. Otherwise things go untested, which is not what > we want. > > ChenYu > >> >> >> Regards >> Martin >> >> >> [0] > http://files.pine64.org/doc/datasheet/pine64/AXP803_Datasheet_V1.0.pdf >> [1] > http://wiki.pine64.org/index.php/PINE_A64_Main_Page#Datasheets_for_Components_and_Peripherals