lkml.org 
[lkml]   [2020]   [Jun]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller
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 = <&regmap>;
>> };
>> };
>>
>> 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

\
 
 \ /
  Last update: 2020-06-09 17:31    [W:1.437 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site