Messages in this thread | | | Date | Tue, 09 Jun 2020 17:30:06 +0200 | From | Michael Walle <> | Subject | Re: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller |
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Am 2020-06-09 17:19, schrieb Lee Jones: > On Tue, 09 Jun 2020, Michael Walle wrote: > >> Am 2020-06-09 08:47, schrieb Lee Jones: >> > On Mon, 08 Jun 2020, Michael Walle wrote: >> > >> > > Am 2020-06-08 20:56, schrieb Lee Jones: >> > > > On Mon, 08 Jun 2020, Michael Walle wrote: >> > > > >> > > > > Am 2020-06-08 12:02, schrieb Andy Shevchenko: >> > > > > > +Cc: some Intel people WRT our internal discussion about similar >> > > > > > problem and solutions. >> > > > > > >> > > > > > On Mon, Jun 8, 2020 at 11:30 AM Lee Jones <lee.jones@linaro.org> wrote: >> > > > > > > On Sat, 06 Jun 2020, Michael Walle wrote: >> > > > > > > > Am 2020-06-06 13:46, schrieb Mark Brown: >> > > > > > > > > On Fri, Jun 05, 2020 at 10:07:36PM +0200, Michael Walle wrote: >> > > > > > > > > > Am 2020-06-05 12:50, schrieb Mark Brown: >> > > > > > >> > > > > > ... >> > > > > > >> > > > > > > Right. I'm suggesting a means to extrapolate complex shared and >> > > > > > > sometimes intertwined batches of register sets to be consumed by >> > > > > > > multiple (sub-)devices spanning different subsystems. >> > > > > > > >> > > > > > > Actually scrap that. The most common case I see is a single Regmap >> > > > > > > covering all child-devices. >> > > > > > >> > > > > > Yes, because often we need a synchronization across the entire address >> > > > > > space of the (parent) device in question. >> > > > > > >> > > > > > > It would be great if there was a way in >> > > > > > > which we could make an assumption that the entire register address >> > > > > > > space for a 'tagged' (MFD) device is to be shared (via Regmap) between >> > > > > > > each of the devices described by its child-nodes. Probably by picking >> > > > > > > up on the 'simple-mfd' compatible string in the first instance. >> > > > > > > >> > > > > > > Rob, is the above something you would contemplate? >> > > > > > > >> > > > > > > Michael, do your register addresses overlap i.e. are they intermingled >> > > > > > > with one another? Do multiple child devices need access to the same >> > > > > > > registers i.e. are they shared? >> > > > > >> > > > > No they don't overlap, expect for maybe the version register, which is >> > > > > just there once and not per function block. >> > > > >> > > > Then what's stopping you having each device Regmap their own space? >> > > >> > > Because its just one I2C device, AFAIK thats not possible, right? >> > >> > Not sure what (if any) the restrictions are. >> >> You can only have one device per I2C address. Therefore, I need one >> device >> which is enumerated by the I2C bus, which then enumerates its >> sub-devices. >> I thought this was one of the use cases for MFD. (Regardless of how a >> sub-device access its registers). So even in the "simple-regmap" case >> this >> would need to be an i2c device.
Here (see below)
>> >> E.g. >> >> &i2cbus { >> mfd-device@10 { >> compatible = "simple-regmap", "simple-mfd"; >> reg = <10>; >> regmap,reg-bits = <8>; >> regmap,val-bits = <8>; >> sub-device@0 { >> compatible = "vendor,sub-device0"; >> reg = <0>; >> }; >> ... >> }; >> >> Or if you just want the regmap: >> >> &soc { >> regmap: regmap@fff0000 { >> compatible = "simple-regmap"; >> reg = <0xfff0000>; >> regmap,reg-bits = <16>; >> regmap,val-bits = <32>; >> }; >> >> enet-which-needs-syscon-too@1000000 { >> vendor,ctrl-regmap = <®map>; >> }; >> }; >> >> Similar to the current syscon (which is MMIO only..). > > We do not need a 'simple-regmap' solution for your use-case. > > Since your device's registers are segregated, just split up the > register map and allocate each sub-device with it's own slice.
I don't get it, could you make a device tree example for my use-case? (see also above)
-michael
> >> > I can't think of any reasons why not, off the top of my head. >> > >> > Does Regmap only deal with shared accesses from multiple devices >> > accessing a single register map, or can it also handle multiple >> > devices communicating over a single I2C channel? >> > >> > One for Mark perhaps.
-- -michael
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