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    SubjectRe: [PATCH v3 7/7] ARM: brcmstb: dts: add a reference DTS for Broadcom 7445
    On 01/16/2014 12:19 PM, Arnd Bergmann wrote:
    > On Thursday 16 January 2014, Marc C wrote:
    >>> And then you can add a regular device driver to drivers/reset that provides a
    >>> device_reset() API to other drivers, or a system-reset function to be registered as
    >>> arm_pm_restart. This driver would use syscon_regmap_lookup_by_phandle() to get access
    >>> to a regmap pointer, and then use either hardcoded offsets into the regmap, or get
    >>> those offsets from numbers in the devicetree, as provided in the example above.
    >>
    >> I was able to port a standalone "reboot" driver using syscon + regmap. However, for the
    >> SMP initialization case, it turns out that syscon is configured after SMP init. Do you
    >> have any advice for this type of situation?
    >>
    >> I'd hate to go around in circles, but without resorting to hard-coded offsets, perhaps I
    >> can just add the remaining "non-regmap" register offsets in the DT?
    >
    > You are not the first one to stumble over this problem. There are
    > two ways to get out of it, and we should probably implement both in
    > the long run:
    >
    > 1. Other platforms also require the syscon driver to be active before
    > the regular device driver probing starts. Michal Simek has the same
    > issue in the zynq clock driver that you have for SMP initialization.
    > We have talked about this with Mark Brown already, and I think we will
    > find a solution for this in the end, but it's not as straightforward
    > as I first hoped. We can probably use help in this area.

    I wouldn't say issue because we have created workaround which should be acceptable.
    For more info.
    https://lkml.org/lkml/2014/1/6/349 patch 2/7 is that what we have done
    to get it work.
    Also I hope that this can go to mainline before any nice solution will be find
    not to stop work on others drivers which use regmap.

    But there is definitely a space for doing this better.


    > 2. There is actually no reason for the SMP code to be called this early,
    > and multiple platforms would like to move SMP init to a later stage.
    > Stephen Boyd has recently started reworking the way we do SMP init,
    > and he may have some more insight.
    >
    > In the meantime, I'd suggest you do the binding under the assumption
    > that it will work eventually, and then work around the current limitations
    > in the SMP code by looking for the device nodes you need and map them
    > manually, as you did in the previous versions of your patch set.

    Yep, that's exactly what we have done just because of other driver developing
    till this is resolved.

    Thanks,
    Michal




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