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From: "Marek Behún" <kabel@kernel.org>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "Pali Rohár" <pali@kernel.org>,
	"Stefan Chulski" <stefanc@marvell.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	"Stefan Roese" <sr@denx.de>, "Phil Sutter" <phil@nwl.cc>,
	"Mario Six" <mario.six@gdsys.cc>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
Subject: Re: [EXT] Re: pci mvebu issue (memory controller)
Date: Wed, 2 Jun 2021 23:59:36 +0200	[thread overview]
Message-ID: <20210602235936.4dac5537@thinkpad> (raw)
In-Reply-To: <20210602211335.oe6r35ctkdtc52ic@pali>

On Wed, 2 Jun 2021 23:13:35 +0200
Pali Rohár <pali@kernel.org> wrote:

> > If the NICs are ordinary PCIe endpoints there must be *something* to
> > terminate the other end of the link.  Maybe it has some sort of
> > non-standard programming interface, but from a PCIe topology point of
> > view, it's a root port.
> > 
> > I don't think I can contribute anything to the stuff below.  It sounds
> > like there's some confusion about how to handle these root ports that
> > aren't exactly root ports.  That's really up to uboot and the mvebu
> > driver to figure out.  
> 
> Yes, I understand, it is non-standard and since beginning I'm also
> confused how this stuff work at all... And this is also reason why
> kernel emulates those root ports (via virtual PCIe bridge devices) to
> present "standard" topology.
> 
> Remaining question is: should really kernel filter that "memory
> controller" device and do not show it in linux PCIe device hierarchy?
> 

Bjorn,

this discussion has gone a little too complex.

The basic issue which Pali tries to solve can be recapitulated:
- there is a "memory controller" device on the "virtual" bus
- Linux' pci-mvebu driver hides this device
- we don't know what is the purpose of this device; it is visible even
  if there is no PCIe device connected
- Pali wants to know what is the purpose of this "memory controller"
  and whether this device should be hidden by Linux and U-Boot, as it
  currently is, or if the controller driver should expose this device

Marek

  reply	other threads:[~2021-06-02 21:59 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210602110703.ymdt6nxsjl7e6glk@pali>
2021-06-02 19:14 ` Bjorn Helgaas
2021-06-02 20:39   ` Pali Rohár
2021-06-02 21:01     ` Bjorn Helgaas
2021-06-02 21:13       ` Pali Rohár
2021-06-02 21:59         ` Marek Behún [this message]
2021-02-09 13:17 Marek Behún
2021-02-10  8:54 ` Thomas Petazzoni
2021-02-10 13:59   ` [EXT] " Stefan Chulski
2021-02-19 17:44     ` Pali Rohár
2021-03-04 18:29       ` Bjorn Helgaas
2021-11-01 18:07         ` Jason Gunthorpe

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