linux-kernel - Re: [PATCH v1 3/7] PCI: New Primary to Sideband (P2SB) bridge support library

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Message-ID: <20210401183236.GN2542@lahna.fi.intel.com>
Date:   Thu, 1 Apr 2021 21:32:36 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Henning Schild <henning.schild@...mens.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Jean Delvare <jdelvare@...e.de>,
        Lee Jones <lee.jones@...aro.org>,
        Tan Jui Nee <jui.nee.tan@...el.com>,
        Jim Quinlan <james.quinlan@...adcom.com>,
        Jonathan Yong <jonathan.yong@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-pci@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        Peter Tyser <ptyser@...-inc.com>, hdegoede@...hat.com
Subject: Re: [PATCH v1 3/7] PCI: New Primary to Sideband (P2SB) bridge
 support library

On Thu, Apr 01, 2021 at 09:22:02PM +0300, Andy Shevchenko wrote:
> On Thu, Apr 01, 2021 at 09:06:17PM +0300, Mika Westerberg wrote:
> > On Thu, Apr 01, 2021 at 06:43:11PM +0300, Andy Shevchenko wrote:
> > > On Sat, Mar 13, 2021 at 10:45:57AM +0100, Henning Schild wrote:
> > > > Am Mon, 8 Mar 2021 14:20:16 +0200
> > > > schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:
> > > 
> > > ...
> > > 
> > > > > + * pci_p2sb_bar - Get Primary to Sideband bridge (P2SB) device BAR
> > > > > + * @pdev:	PCI device to get a PCI bus to communicate with
> > > > > + * @devfn:	PCI slot and function to communicate with
> > > > > + * @mem:	memory resource to be filled in
> > > > 
> > > > Do we really need that many arguments to it?
> > > > 
> > > > Before i had, in a platform driver that never had its own pci_dev or bus
> > > > 
> > > >   res->start = simatic_ipc_get_membase0(PCI_DEVFN(13, 0));
> > > >   if (res-start == 0)
> > > >     return -ENODEV;
> > > > 
> > > > So helper only asked for the devfn, returned base and no dedicated
> > > > error code.
> > > > 
> > > > With this i need
> > > > 
> > > >   struct pci_bus *bus = pci_find_bus(0, 0);
> > > >   struct pci_dev *pci_dev = bus->self;
> > > >   unsigned int magic_i_do_not_want =  PCI_DEVFN(13, 0);
> > > 
> > > What confuses me is the use for SPI NOR controller on Broxton. And I think
> > > we actually can indeed hide all this under the hood by exposing P2SB to the OS.
> > > 
> > > Mika, what do you think?
> > 
> > Not sure I follow. Do you mean we force unhide P2SB and then bind (MFD)
> > driver to that?
> 
> Not MFD, SPI NOR (if I understood correctly the code in MFD driver for SPI NOR
> in regards to P2SB case).

I mean a new MFD driver that binds to the P2SB and that one then exposes
the stuff needed by the SPI-NOR driver.