linux-kernel - Re: [PATCH v9 5/7] ACPI: Translate the I/O range of non-MMIO devices before scanning

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Message-ID: <b2bc9134-9944-bd6a-2daf-8f1a1ff49a62@huawei.com>
Date:   Fri, 30 Jun 2017 10:28:36 +0100
From:   John Garry <john.garry@...wei.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Gabriele Paoloni <gabriele.paoloni@...wei.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "frowand.list@...il.com" <frowand.list@...il.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "brian.starkey@....com" <brian.starkey@....com>,
        "olof@...om.net" <olof@...om.net>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "minyard@....org" <minyard@....org>,
        "xuwei (O)" <xuwei5@...ilicon.com>
Subject: Re: [PATCH v9 5/7] ACPI: Translate the I/O range of non-MMIO devices
 before scanning

On 30/06/2017 10:05, Mika Westerberg wrote:
> On Thu, Jun 29, 2017 at 05:16:15PM +0100, John Garry wrote:
>> On 16/06/2017 12:24, Rafael J. Wysocki wrote:
>>>>>>>>>
>>>>>>>>> It causes acpi_default_enumeration() to be called but it should be fine
>>>>>>>>> as we are dealing with platform device anyway.
>>>>>>>
>>>>>>> I do not quite understand how declaring such MFD cell above would make sure
>>>>>>> that the LPC probe is called before the IPMI device is enumerated...
>>>>>
>>>>> In fact it may be that it is not sufficient in this case because the
>>>>> ACPI core might enumerate child devices before the LPC driver even gets
>>>>> a chance to probe so you would need to add also scan handler to the
>>>>> child devices and mark them already enumerated or something like that.
>>> Or extend the special I2C/SPI handling to them.
>>>
>>
>> For this, is it possible to just configure the ACPI table so we spoof that
>> the LPC slave (IPI0001), is an i2c/spi slave? Could we just add a resource
>> of type ACPI_RESOURCE_TYPE_SERIAL_BUS, and common serial bus type i2c/spi to
>> solve this?
>
> But is the device connected to a I2C or SPI bus? If not, then it does
> not make much sense to declare it as I2C or SPI slave. Instead it should
> be platform device which is the type we use when there is no explicit
> bus specified in ACPI.
>

No, it's not a SPI nor an I2C bus. I actually would say that my idea is 
generally wrong, as the ACPI definition is not a real reflection of the 
bus/slave.

However, Rafael did suggest extending special I2C/SPI handling to them. 
In this case, I don't see how the LPC slave can be identified like an 
I2C or SPI slave is.

Thanks,
John

> .
>