linux-kernel - RE: [patch v1] x86/platform/mellanox: introduce support for Mellanox systems platform

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Date:   Mon, 12 Sep 2016 08:44:57 +0000
From:   Vadim Pasternak <vadimp@...lanox.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "geert@...ux-m68k.org" <geert@...ux-m68k.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "linux@...ck-us.net" <linux@...ck-us.net>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "jiri@...nulli.us" <jiri@...nulli.us>
Subject: RE: [patch v1] x86/platform/mellanox: introduce support for Mellanox
 systems platform



> -----Original Message-----
> From: Greg KH [mailto:gregkh@...uxfoundation.org]
> Sent: Monday, September 12, 2016 11:35 AM
> To: Vadim Pasternak <vadimp@...lanox.com>
> Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> davem@...emloft.net; geert@...ux-m68k.org; akpm@...ux-foundation.org;
> kvalo@...eaurora.org; mchehab@...nel.org; linux@...ck-us.net;
> x86@...nel.org; linux-kernel@...r.kernel.org; platform-driver-
> x86@...r.kernel.org; jiri@...nulli.us
> Subject: Re: [patch v1] x86/platform/mellanox: introduce support for Mellanox
> systems platform
> 
> On Mon, Sep 12, 2016 at 08:21:28AM +0000, Vadim Pasternak wrote:
> >
> >
> > > -----Original Message-----
> > > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > > Sent: Monday, September 12, 2016 11:17 AM
> > > To: Vadim Pasternak <vadimp@...lanox.com>
> > > Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> > > davem@...emloft.net; geert@...ux-m68k.org;
> > > akpm@...ux-foundation.org; kvalo@...eaurora.org; mchehab@...nel.org;
> > > linux@...ck-us.net; x86@...nel.org; linux-kernel@...r.kernel.org;
> > > platform-driver- x86@...r.kernel.org; jiri@...nulli.us
> > > Subject: Re: [patch v1] x86/platform/mellanox: introduce support for
> > > Mellanox systems platform
> > >
> > > On Mon, Sep 12, 2016 at 07:48:24AM +0000, Vadim Pasternak wrote:
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > > > > Sent: Monday, September 12, 2016 10:41 AM
> > > > > To: Vadim Pasternak <vadimp@...lanox.com>
> > > > > Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> > > > > davem@...emloft.net; geert@...ux-m68k.org;
> > > > > akpm@...ux-foundation.org; kvalo@...eaurora.org;
> > > > > mchehab@...nel.org; linux@...ck-us.net; x86@...nel.org;
> > > > > linux-kernel@...r.kernel.org;
> > > > > platform-driver- x86@...r.kernel.org; jiri@...nulli.us
> > > > > Subject: Re: [patch v1] x86/platform/mellanox: introduce support
> > > > > for Mellanox systems platform
> > > > >
> > > > > On Mon, Sep 12, 2016 at 07:23:59AM +0000, Vadim Pasternak wrote:
> > > > > >
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > > > > > > Sent: Monday, September 12, 2016 10:05 AM
> > > > > > > To: Vadim Pasternak <vadimp@...lanox.com>
> > > > > > > Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> > > > > > > davem@...emloft.net; geert@...ux-m68k.org;
> > > > > > > akpm@...ux-foundation.org; kvalo@...eaurora.org;
> > > > > > > mchehab@...nel.org; linux@...ck-us.net; x86@...nel.org;
> > > > > > > linux-kernel@...r.kernel.org;
> > > > > > > platform-driver- x86@...r.kernel.org; jiri@...nulli.us
> > > > > > > Subject: Re: [patch v1] x86/platform/mellanox: introduce
> > > > > > > support for Mellanox systems platform
> > > > > > >
> > > > > > > On Mon, Sep 12, 2016 at 06:44:03AM +0000, Vadim Pasternak wrote:
> > > > > > > >
> > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: Greg KH [mailto:gregkh@...uxfoundation.org]
> > > > > > > > > Sent: Monday, September 12, 2016 9:13 AM
> > > > > > > > > To: Vadim Pasternak <vadimp@...lanox.com>
> > > > > > > > > Cc: tglx@...utronix.de; mingo@...hat.com; hpa@...or.com;
> > > > > > > > > davem@...emloft.net; geert@...ux-m68k.org;
> > > > > > > > > akpm@...ux-foundation.org; kvalo@...eaurora.org;
> > > > > > > > > mchehab@...nel.org; linux@...ck-us.net; x86@...nel.org;
> > > > > > > > > linux-kernel@...r.kernel.org;
> > > > > > > > > platform-driver- x86@...r.kernel.org; jiri@...nulli.us
> > > > > > > > > Subject: Re: [patch v1] x86/platform/mellanox: introduce
> > > > > > > > > support for Mellanox systems platform
> > > > > > > > >
> > > > > > > > > On Mon, Sep 12, 2016 at 06:29:58AM +0000,
> > > > > > > > > vadimp@...lanox.com
> > > > > wrote:
> > > > > > > > > > From: Vadim Pasternak <vadimp@...lanox.com>
> > > > > > > > > >
> > > > > > > > > > Enable system support for the Mellanox Technologies
> > > > > > > > > > platform, which provides support for the next Mellanox
> > > > > > > > > > basic
> > > systems:
> > > > > > > > > > "msx6710", "msx6720", "msb7700", "msn2700", "msx1410",
> > > > > > > > > > "msn2410", "msb7800", "msn2740", "msn2100" and also
> > > > > > > > > > various number of derivative systems from the above basic
> types.
> > > > > > > > >
> > > > > > > > > What does "system support" mean?
> > > > > > > > >
> > > > > > > > > Why can't this just be a "normal" PCI driver, as you are
> > > > > > > > > just accessing a PCI device and doing something with it,
> > > > > > > > > seems odd to claim it is a
> > > > > > > "platform" driver.
> > > > > > > > >
> > > > > > > >
> > > > > > > > This driver also activates probes to create i2c platform
> > > > > > > > driver and
> > > muxes.
> > > > > > >
> > > > > > > And how does it do that?  Through the PCI device?
> > > > > > >
> > > > > > > > For ARM and PPC based systems I can activate such stuff through
> dts.
> > > > > > > > To be honest I don't know what is the right way to do such
> > > > > > > > things for
> > > > > > > > x86 systems.
> > > > > > >
> > > > > > > How is it found in a x86 system, in ACPI?
> > > > > > >
> > > > > >
> > > > > > We have no support in ACPI.
> > > > > > Currently it could be found through DMI.
> > > > > >
> > > > > > > > If I will move PCI related stuff to separate driver, could
> > > > > > > > you suggest some right location for that?
> > > > > > >
> > > > > > > Depends on what it does.
> > > > > >
> > > > > > It creates platform i2c driver (Mellanox controller), like:
> > > > > > platform_device_register_simple("i2c_mlxcpld", -1,
> > > > > >                                                          NULL,
> > > > > > 0); And two mux platform device instances, like:
> > > > > > platform_device_register_resndata(dev,
> > > > > >                                                 " i2c-mux-reg", i, NULL,
> > > > > >                                                 0,
> > > > > > &mlxplat_mux_data[i],
> > > > > >
> > > > > > sizeof(mlxplat_mux_data[i]));
> > > > >
> > > > > Ugh.  Really?  These aren't on a real bus?  What is this, the 1990's?
> > > >
> > > > Actually this is 2015-2016.
> > > > Many switches use i2c virtual buses infrastructure for placing
> > > > slow devices for system monitoring and control.
> > >
> > > Yes, but that i2c controller is on what type of bus?  A non-discoverable one?
> > > That's what I'm complaining about...
> >
> > This is LPC to I2C bridge.
> 
> "LPC"?
> 
> > Controller logic is implemented in Lattice CPLD. CPLD itself is attached to LPC.
> 
> And how is the CPLD attached to the CPU?

This is how it connected on Celeron, I7, ATOM based systems:

*--------*
| I2CLPC | i2c physical
| bridge | bus                          *---------*
| logic  |---------------------> * mux reg *
| in CPLD|                                *---------*
*--------*
    |
    |
<-------->
i2c cntrl
reg space
    | 
    |
    *------------- LPC bus ----------------- CPU