Message-ID: <44033A2D.9000902@pobox.com>
Date: Mon, 27 Feb 2006 12:43:09 -0500
From: Jeff Garzik <jgarzik@pobox.com>
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To: Kenji Kaneshige <kaneshige.kenji@soft.fujitsu.com>,
       Andrew Morton <akpm@osdl.org>, Greg KH <greg@kroah.com>
CC: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-pci@atrey.karlin.mff.cuni.cz, Andi Kleen <ak@suse.de>,
       benh@kernel.crashing.org,
       Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Subject: Re: [PATCH 0/4] PCI legacy I/O port free driver (take 3)
References: <44028502.4000108@soft.fujitsu.com>
In-Reply-To: <44028502.4000108@soft.fujitsu.com>
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Kenji Kaneshige wrote:
> Hi,
> 
> Here is an updated set of patches for PCI legacy I/O port free drivers
> which incorporates feedbacks. Summary of changes from the previous
> version are:
> 
>     - Removed the device_flags field from struct pci_device_id, which
>       was introduced in the previous version of patch
> 
>     - Changed e1000 driver to use the driver_data field in struct
>       pci_device_id to see if the device needs I/O port regions.
> 
>     - Added proper messages instead of WARN_ON() at the error.
> 
>     - Updated the Documentation/pci.txt
> 
> I'm attaching the following four patches:
> 
>     [patch 1/4] Add no_ioport flag into pci_dev
>     [patch 2/4] Update Documentation/pci.txt
>     [patch 3/4] Make Intel e1000 driver legacy I/O port free
>     [patch 4/4] Make Emulex lpfc driver legacy I/O port free
> 
> I'm attaching the brief description below about what the problem I'm
> trying to solve is.
> 
> Thanks,
> Kenji Kaneshige
> 
> 
> Brief Description
> ~~~~~~~~~~~~~~~~~
> I encountered a problem that some PCI devices don't work on my system
> which have huge number of PCI devices.
> 
> It is mandatory for all PCI device drivers to enable the device by
> calling pci_enable_device() which enables all regions probed from the
> device's BARs. If pci_enable_device() failes to enable any regions
> probed from BARs, it returns as error. On the large servers, I/O port
> resource could not be assigned to all PCI devices because it is
> limited (64KB on Intel Architecture[1]) and it would be fragmented
> (I/O base register of PCI-to-PCI bridge will usually be aligned to a
> 4KB boundary[2]). In this case, the devices which have no I/O port
> resource assigned don't work because pci_enable_device() for those
> devices failes. This is what happened on my machine.

This series still leaves a lot to be desired, and creates unnecessary
driver churn.  The better solution is:

1) pci_enable_device() enables what it can

2) Drivers, as they already do, will fail if they cannot map the desired
memory or IO resources that are needed.

Thus, the PCI layer needs only to do #1, and existing driver code
handles the rest of the situation as one currently expects.

	Jeff


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