linux-kernel - Re: [PATCH v2 0/2] PCI: Add support for PCI Enhanced Allocation "BARs"

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Message-ID: <56034505.1080301@gmail.com>
Date:	Wed, 23 Sep 2015 17:34:13 -0700
From:	David Daney <ddaney.cavm@...il.com>
To:	"Sean O. Stalley" <sean.stalley@...el.com>
CC:	bhelgaas@...gle.com, yinghai@...nel.org, rajatxjain@...il.com,
	mst@...hat.com, zajec5@...il.com, gong.chen@...ux.intel.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v2 0/2] PCI: Add support for PCI Enhanced Allocation "BARs"

Hi Sean,

Thanks for doing this, I think we will use it for Cavium ThunderX.  A 
couple of questions...


On 09/23/2015 03:27 PM, Sean O. Stalley wrote:
> PCI Enhanced Allocation is a new method of allocating MMIO & IO
> resources for PCI devices & bridges. It can be used instead
> of the traditional PCI method of using BARs.
>
> EA entries are hardware-initialized to a fixed address.
> Unlike BARs, regions described by EA are cannot be moved.
> Because of this, only devices which are permanently connected to
> the PCI bus can use EA. A removable PCI card must not use EA.
>
> This patchset adds support for using EA entries instead of BARs
> on Root Complex Integrated Endpoints.
>
> The Enhanced Allocation ECN is publicly available here:
> https://www.pcisig.com/specifications/conventional/ECN_Enhanced_Allocation_23_Oct_2014_Final.pdf
>
>
> Changes from V1:
> 	- Use generic PCI resource claim functions (instead of EA-specific functions)
> 	- Only add support for RCiEPs (instead of all devices).

Why not all devices?  The spec. allows for EA on devices behind bridges.


> 	- Removed some debugging messages leftover from early testing.
>
>
> Sean O. Stalley (2):
>    PCI: Add Enhanced Allocation register entries
>    PCI: Add support for Enhanced Allocation devices
>
>   drivers/pci/pci.c             | 174 ++++++++++++++++++++++++++++++++++++++++++
>   drivers/pci/pci.h             |   1 +
>   drivers/pci/probe.c           |   3 +
>   include/uapi/linux/pci_regs.h |  40 +++++++++-
>   4 files changed, 217 insertions(+), 1 deletion(-)
>

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