Hi Mika

-----Original Message-----
From: linux-pci-owner at vger.kernel.org [mailto:linux-pci-
owner at vger.kernel.org] On Behalf Of Mika Westerberg
Sent: 13 June 2017 21:04
To: Gabriele Paoloni
Cc: Lorenzo Pieralisi; rafael at kernel.org; Rafael J. Wysocki;
catalin.marinas at arm.com; will.deacon at arm.com; robh+dt at kernel.org;
frowand.list at gmail.com; bhelgaas at google.com; arnd at arndb.de; linux-arm-
kernel at lists.infradead.org; mark.rutland at arm.com;
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kernel at vger.kernel.org; linux-acpi at vger.kernel.org; Linuxarm; linux-
pci at vger.kernel.org; minyard at acm.org; John Garry; xuwei (O)
Subject: Re: [PATCH v9 5/7] ACPI: Translate the I/O range of non-MMIO
devices before scanning

On Tue, Jun 13, 2017 at 07:01:38PM +0000, Gabriele Paoloni wrote:

quoted

I am not very familiar with Linux MFD however the main issue here is

that

quoted

1) for IPMI we want to re-use the standard IPMI driver without

touching it:

quoted

   see

   static const struct acpi_device_id acpi_ipmi_match[] = {
         { "IPI0001", 0 },
         { },
   };

   in "drivers/char/ipmi/ipmi_si_intf.c" (and in general any standard

driver

quoted

   of an LPC child)

2) We need a way to guarantee that all LPC children are not

enumerated

quoted

   by acpi_default_enumeration() (so for example if an ipmi node is

an LPC#

quoted

   child it should not be enumerated, otherwise it should be)
   Currently acpi_default_enumeration() skips spi/i2c slaves by

checking:

quoted

   1) if the acpi resource type is a serial bus
   2) if the type of serial bus descriptor is I2C or SPI

   For LPC we cannot leverage on any ACPI property to "recognize"

that our

quoted

   devices are LPC children; hence before I proposed for

acpi_default_enumeration()

quoted

   to skip devices that have already been enumerated (by calling
   acpi_device_enumerated() ).

So in the current scenario, how do you think that MFD can help?

If you look at Documentation/acpi/enumeration.txt there is a chapter
"MFD devices". I think it pretty much maches what you have here. An LPC
device (MFD device) and bunch of child devices. The driver for your LPC
device can specify _HID for each child device. Those are then mached by
the MFD ACPI code to the corresponding ACPI nodes from which platform
devices are created including "IPI0001".

So I guess here in the LPC driver I would have an MFD cell for IPMI. I.e.:

	static struct mfd_cell_acpi_match hisi_lpc_ipmi_acpi_match = {
		.pnpid = "IPI0001",
	};

correct?

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...

Could you point me to the code that does this?

Many Thanks
Gab

Once the platform device is created your ipmi driver will be probed by
the driver core.

Does that make sense?