linux-kernel - Re: [PATCH] HISI LPC: Add Kconfig MFD

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Message-ID: <CAK8P3a2rfFvQdSaGjqtk=kz75tW9JNFdqeUiX6JBWJdM658T2Q@mail.gmail.com>
Date:   Thu, 19 Apr 2018 15:29:13 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     John Garry <john.garry@...wei.com>
Cc:     "xuwei (O)" <xuwei5@...wei.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Simon Horman <horms+renesas@...ge.net.au>,
        gregkh <gregkh@...uxfoundation.org>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Robin Murphy <robin.murphy@....com>,
        Sebastien Bourdelin <sebastien.bourdelin@...oirfairelinux.com>,
        bogdan.purcareata@....com, Tony Lindgren <tony@...mide.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Olof Johansson <olof@...om.net>,
        Kevin Hilman <khilman@...nel.org>, tanxiaojun@...wei.com
Subject: Re: [PATCH] HISI LPC: Add Kconfig MFD_CORE dependency

On Thu, Apr 19, 2018 at 3:08 PM, John Garry <john.garry@...wei.com> wrote:
> On 19/04/2018 13:00, Arnd Bergmann wrote:
>>
>> On Thu, Apr 19, 2018 at 1:55 PM, John Garry <john.garry@...wei.com> wrote:
>>>
>>> For ACPI support of the HiSilicon LPC driver we depend
>>> on MFD_CORE config.
>>>
>>> Currently the HiSi LPC Kconfig entry does not define this
>>> dependency, so add it.
>>>
>>> Fixes: e0aa1563f894 ("HISI LPC: Add ACPI support")
>>> Reported-and-tested-by: Tan Xiaojun <tanxiaojun@...wei.com>
>>> Signed-off-by: John Garry <john.garry@...wei.com>
>>
>>
>> Can you explain the specific dependency? Normally MFD_CORE gets
>> selected by an MFD driver but not other drivers.
>>
>
> For each device on the LPC bus we create an MFD.
>
> The reason we do this is that we need to set the resources of the derived
> MFD, as we should not modify the original ACPI device created in ACPI scan.
> Details are in the log for e0aa1563f894.
>
> Shall I update commit message updated with this info? Or were you just
> interested in the motivation for using MFD?

I think it would be good to update the description. I had missed the part
where an LPC device becomes a platform_device through an mfd_cell
rather than becoming a device with bus_type=&isa_bus_type as I think
was the case in earlier versions of your patch series.

     Arnd