Messages in this thread | | | Date | Tue, 09 Jun 2020 16:38:31 +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 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.
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..).
-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. > >> > The issues I wish to resolve using 'simple-mfd' are when sub-devices >> > register maps overlap and intertwine. > > [...] > >> > > > > What do these bits configure? >> > > >> > > - hardware strappings which have to be there before the board powers >> > > up, >> > > like clocking mode for different SerDes settings >> > > - "keep-in-reset" bits for onboard peripherals if you want to save >> > > power >> > > - disable watchdog bits (there is a watchdog which is active right >> > > from >> > > the start and supervises the bootloader start and switches to >> > > failsafe >> > > mode if it wasn't successfully started) >> > > - special boot modes, like eMMC, etc. >> > > >> > > Think of it as a 16bit configuration word. >> > >> > And you wish for users to be able to view these at run-time? >> >> And esp. change them. >> >> > Can they adapt any of them on-the-fly or will the be RO? >> >> They are R/W but only will only affect the board behavior after a >> reset. > > I see. Makes sense. This is board controller territory. Perhaps > suitable for inclusion into drivers/soc or drivers/platform.
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