linux-kernel - Re: [PATCH v3 35/36] platform/x86: intel_pmc

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Message-ID: <20200120130719.GO2665@lahna.fi.intel.com>
Date:   Mon, 20 Jan 2020 15:07:19 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Zha Qipeng <qipeng.zha@...el.com>,
        "David E . Box" <david.e.box@...ux.intel.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 35/36] platform/x86: intel_pmc_ipc: Convert to MFD

On Mon, Jan 20, 2020 at 12:50:59PM +0000, Lee Jones wrote:
> On Mon, 20 Jan 2020, Mika Westerberg wrote:
> > On Mon, Jan 20, 2020 at 11:14:50AM +0000, Lee Jones wrote:
> > > On Mon, 20 Jan 2020, Mika Westerberg wrote:
> > > 
> > > > On Mon, Jan 20, 2020 at 08:12:46AM +0000, Lee Jones wrote:
> > > > > > Well, by "library" I mean that the SCU IPC itself does not bind to
> > > > > > anything but instead it gets called by different drivers such as this
> > > > > > one passing the device pointer that is the SCU IPC device. Here for
> > > > > > example it is the platfrom device created from an ACPI description.
> > > > > 
> > > > > Not keen on that at all.  Why can it not be a platform device?
> > > > 
> > > > We also call the same library from a PCI driver (intel_scu_pcidrv.c in
> > > > this series) where the device is of type struct pci_dev.
> > > 
> > > Not sure I understand the issue.
> > 
> > You are asking why it cannot be a platform device. It cannot be because
> > we are calling the same library from a PCI driver where there is no
> > platform device available (only struct pci_dev).
> 
> I'm asking why it needs to be called at all.  Why can't it be probed
> using the Device Driver API, like most other drivers?

The PMC is a single device (either ACPI or PCI) that includes SCU IPC
and zero or more child devices sharing the resources (hence I'm
converting it to MFD in the first place).

I want to use the same SCU IPC implementation from both the PCI driver
(intel_scu_pcidrv.c) and the MFD driver (intel_pmc_bxt.c).