Re: Patch "syscon: Decrease driver registration priority" breaks clps711x target

[Andrey Smirnov <andrew.smirnov@gmail.com>]

On Wed, Jul 13, 2016 at 10:57 AM, Trent Piepho <tpiepho@kymetacorp.com> wrote:
> On Wed, 2016-07-13 at 08:52 -0700, Andrey Smirnov wrote:
>> On Wed, Jul 13, 2016 at 6:04 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
>> > On Wed, Jul 13, 2016 at 10:37:11AM +0300, Alexander Shiyan wrote:
>> >> Hello All.
>> >>
>> >> Patch "syscon: Decrease driver registration priority" breaks clps711x target.
>> >> Previously, the syscon device initialized at "core_initcall", that did not cause problems.
>> >> Now the device is initialized at "device_initcall" level, but clps711x uses syscon for
>> >> the serial, so serial device initialized at "console_initcall" level.
>> >> Any ideas?
>> >
>> > We could move syscon back to core_initcall level and in the syscon
>> > driver use dev_get_resource() instead of request_iomem_region().
>>
>> Right now the driver uses both, so if we just drop the call to
>> request_iomem_region that was problematic for me on i.MX6, that should
>> resolve the issue. I think this would also bring the behavior of
>> syscon driver closer to what it does in Linux kernel land. The only
>> negative effect of that change I think would be that on the platforms
>> where syscon driver controls that region of memory, it no longer would
>> be reported as such by "iomem".
>>
>
> Syscon driver is a little strange in Linux since commit bdb0066.  The
> driver no longer as an OF match and doesn't bind to syscon devices
> listed in the device tree.  When something wants to use a syscon it
> calls syscon_regmap_lookup_by_compatible(), which finds the OF node,
> maps the registers, and puts it in a driver global list.  Anything that
> maps the same syscon will get the same regmap that via the list.  But
> the regmap is never associated with the syscon device!
>
> So syscon doesn't use the driver/device model anymore.  It's more like a
> global table of regmaps that are indexed using a OF node.

Good to know, thanks for the info. When I was looking at that code
earlier I was looking at the stable 4.4 kernel, so my knowledge of it
is probably outdated. I'll take a look again when I get to work on the
patch.

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