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From: Mark Brown <broonie@kernel.org>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	Takashi Iwai <tiwai@suse.de>,
	Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
	Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
	davem@davemloft.net, netdev@vger.kernel.org,
	linux-rdma@vger.kernel.org, nhorman@redhat.com,
	sassmann@redhat.com, Fred Oh <fred.oh@linux.intel.com>,
	lee.jones@linaro.org
Subject: Re: [net-next v4 10/12] ASoC: SOF: Introduce descriptors for SOF client
Date: Tue, 30 Jun 2020 15:16:04 +0100	[thread overview]
Message-ID: <20200630141604.GJ5272@sirena.org.uk> (raw)
In-Reply-To: <20200630113245.GG25301@ziepe.ca>

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On Tue, Jun 30, 2020 at 08:32:45AM -0300, Jason Gunthorpe wrote:
> On Tue, Jun 30, 2020 at 11:31:41AM +0100, Mark Brown wrote:
> > On Mon, Jun 29, 2020 at 07:59:59PM -0300, Jason Gunthorpe wrote:

> > > > What are we supposed to do with things like PCI attached FPGAs and ASICs
> > > > in that case?  They can have host visible devices with physical
> > > > resources like MMIO ranges and interrupts without those being split up
> > > > neatly as PCI subfunctions - the original use case for MFD was such
> > > > ASICs, there's a few PCI drivers in there now. 

> > > Greg has been pretty clear that MFD shouldn't have been used on top of
> > > PCI drivers.

> > The proposed bus lacks resource handling, an equivalent of
> > platform_get_resource() and friends for example, which would be needed
> > for use with physical devices.  Both that and the name suggest that it's
> > for virtual devices.

> Resource handling is only useful if the HW has a hard distinction
> between it's functional blocks. This scheme is intended for devices
> where that doesn't exist. The driver that attaches to the PCI device
> and creates the virtual devices is supposed to provide SW abstractions
> for the other drivers to sit on.

> I'm not sure why we are calling it virtual bus.

The abstraction that the PCI based MFDs (and FPGAs will be similar,
they're just dynamic MFDs to a good approximation) need is to pass
through MMIO regions, interrupts and so on which is exactly what the
platform bus offers.  The hardware is basically someone taking a bunch
of IPs and shoving them behind the MMIO/interrupt regions of a PCI
device.

> > The reason the MFDs use platform devices is that they end up having to
> > have all the features of platform devices - originally people were
> > making virtual buses for them but the code duplication is real so
> > everyone (including Greg) decided to just use what was there already.

> Maybe Greg will explain why he didn't like the earlier version of that
> stuff that used MFD

AFAICT Greg is mostly concerned about the MFDs that aren't memory
mapped, though some of them do use the resource API to pass interrupts
through.

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  reply	other threads:[~2020-06-30 14:16 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-20  7:02 [net-next v4 00/12][pull request] 100GbE Intel Wired LAN Driver Updates 2020-05-19 Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 01/12] Implementation of Virtual Bus Jeff Kirsher
2020-05-21 14:57   ` Parav Pandit
2020-05-21 17:43     ` gregkh
2020-05-21 20:10       ` Jason Gunthorpe
2020-05-20  7:02 ` [net-next v4 02/12] ice: Create and register virtual bus for RDMA Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 03/12] ice: Complete RDMA peer registration Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 04/12] ice: Support resource allocation requests Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 05/12] ice: Enable event notifications Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 06/12] ice: Allow reset operations Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 07/12] ice: Pass through communications to VF Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 08/12] i40e: Move client header location Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 09/12] i40e: Register a virtbus device to provide RDMA Jeff Kirsher
2020-05-20  7:02 ` [net-next v4 10/12] ASoC: SOF: Introduce descriptors for SOF client Jeff Kirsher
2020-05-20  7:20   ` Greg KH
2020-05-20 12:54   ` Jason Gunthorpe
2020-05-20 12:57     ` Jason Gunthorpe
2020-05-21 21:11     ` Ranjani Sridharan
2020-05-21 23:34       ` Jason Gunthorpe
2020-05-22 14:29         ` Pierre-Louis Bossart
2020-05-22 14:55           ` Jason Gunthorpe
2020-05-22 15:33             ` Pierre-Louis Bossart
2020-05-22 17:10               ` Jason Gunthorpe
2020-05-22 18:35                 ` Pierre-Louis Bossart
2020-05-22 18:40                   ` Jason Gunthorpe
2020-05-22 18:48                     ` Pierre-Louis Bossart
2020-05-22 19:44                       ` Jason Gunthorpe
2020-05-22 21:05                         ` Pierre-Louis Bossart
2020-06-29 20:59               ` Mark Brown
2020-05-23  6:23           ` Greg KH
2020-05-23 19:41             ` Pierre-Louis Bossart
2020-05-24  6:35               ` Greg KH
2020-05-26 13:15                 ` Pierre-Louis Bossart
2020-05-26 13:37                   ` Takashi Iwai
2020-05-27  7:17                     ` Greg KH
2020-05-27 14:05                       ` Pierre-Louis Bossart
2020-06-29 20:33                       ` Mark Brown
2020-06-29 22:59                         ` Jason Gunthorpe
2020-06-29 23:13                           ` Kirsher, Jeffrey T
2020-06-30 10:31                           ` Mark Brown
2020-06-30 11:32                             ` Jason Gunthorpe
2020-06-30 14:16                               ` Mark Brown [this message]
2020-06-30 17:24                               ` Ranjani Sridharan
2020-06-30 17:27                                 ` Jason Gunthorpe
2020-07-01  9:50                                   ` Mark Brown
2020-07-01 23:32                                     ` Jason Gunthorpe
2020-07-02 11:15                                       ` Mark Brown
2020-07-02 12:11                                         ` Jason Gunthorpe
2020-07-02 12:20                                           ` Mark Brown
2020-07-01  6:59                                 ` Greg KH
2020-07-02 13:43                                   ` Ranjani Sridharan
2020-07-06 23:02                                     ` Dan Williams
2020-07-07 14:16                                       ` Greg KH
2020-05-25 16:55               ` Jason Gunthorpe
2020-06-29 20:21             ` Mark Brown
2020-06-29 17:36   ` Mark Brown
2020-05-20  7:02 ` [net-next v4 11/12] ASoC: SOF: Create client driver for IPC test Jeff Kirsher
2020-05-20  7:22   ` Greg KH
2020-05-20 12:56   ` Jason Gunthorpe
2020-05-27 20:18     ` Ranjani Sridharan
2020-05-28  0:12       ` Jason Gunthorpe
2020-05-28  1:40         ` Ranjani Sridharan
2020-05-28 10:45           ` Greg KH
2020-06-29 20:37             ` Mark Brown
2020-05-20  7:02 ` [net-next v4 12/12] ASoC: SOF: ops: Add new op for client registration Jeff Kirsher
2020-05-20  7:23   ` Greg KH
2020-05-20  7:17 ` [net-next v4 00/12][pull request] 100GbE Intel Wired LAN Driver Updates 2020-05-19 Greg KH
2020-05-20  7:25   ` Kirsher, Jeffrey T
2020-05-20  9:08     ` Greg KH

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