linux-kernel - Re: [PATCH 4/4] PCI: make cardbus-bridge resources nice-to-have

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Date:	Wed, 22 Jun 2011 00:13:01 +0200
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Ram Pai <linuxram@...ibm.com>, linux-kernel@...r.kernel.org,
	linux-mmc@...r.kernel.org, svenkatr@...com, yinghai@...nel.org,
	cjb@...top.org, linux-pci@...r.kernel.org,
	linux-net-drivers@...arflare.com, bhutchings@...arflare.com
Subject: Re: [PATCH 4/4] PCI: make cardbus-bridge resources nice-to-have

Hey,

On Tue, Jun 21, 2011 at 02:36:22PM -0700, Jesse Barnes wrote:
> On Tue, 21 Jun 2011 09:23:21 -0700
> Ram Pai <linuxram@...ibm.com> wrote:
> 
> > On Tue, Jun 21, 2011 at 09:57:00AM +0200, Dominik Brodowski wrote:
> > > On Mon, Jun 20, 2011 at 03:47:17PM -0700, Ram Pai wrote:
> > > > Allocate resources to cardbus bridge only after all other genuine
> > > > resources requests are satisfied. Dont retry if resource allocation
> > > > for cardbus-bridge fails.
> > > 
> > > Well, for those who use cardbus cards, cardbus resources aren't "nice to
> > > have", they are absolutely required. Of course, not all cardbus cards need
> > > as many resources as are currently assigned, so I wouldn't oppose a patch
> > > which marks _some_ of the currently assigned resources as "nice to have".
> > > But this approach -- 0 required, all "nice to have" -- seems wrong to me.
> > 
> > Do you know how much minimal resource is good enough?  The value, before
> > this patch, was 256 for IO ports and  64M for memory.
> > 
> > BTW: If the BIOS has already assigned enough resources for all the devices on
> > the system, no devices will be starved including the cardbus. The OS intervenes
> > and is forced to make this hard choice only when it sees unassigned resources to
> > some devices along with resource contention.
> 
> Dominik, presumably you have a few good cardbus test machines; can you
> give Ram's patches a try?  If we know they break existing
> configurations, I'm afraid we'll just have to revert the whole
> re-allocation patch yet again.  If your stuff survives, I'll ping Linus
> to see what he thinks, though he'll probably want to revert in any
> case...

Actually, I only have one cardbus-capable test machine, which does work in
very most cases, and also I do care much more about the PCMCIA side of
things than the PCI/CardBus side... Therefore, all I could do is some more
or less informed guessing about how much minimal resource we should try to
allocate...

Best,
	Dominik
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