From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH 1/1] pci: xgene: Enable huge outbound bar support
Date: Fri, 26 Jun 2015 22:43:32 +0200
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To: Duc Dang <dhdang@apm.com>
Cc: linux-arm <linux-arm-kernel@lists.infradead.org>, Bjorn Helgaas <bhelgaas@google.com>, Catalin Marinas <catalin.marinas@arm.com>, Ian Campbell <ijc+devicetree@hellion.org.uk>, Pawel Moll <pawel.moll@arm.com>, Rob Herring <robh+dt@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Kumar Gala <galak@codeaurora.org>, Will Deacon <will.deacon@arm.com>, "David S. Miller" <davem@davemloft.net>, devicetree@vger.kernel.org, linux-pci@vger.kernel.org, patches <patches@apm.com>, linux-kernel@vger.kernel.org, Tanmay Inamdar <tinamdar@apm.com>
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On Friday 26 June 2015 22:35:08 Arnd Bergmann wrote:
> > >
> > > Can you configure one of the two windows as prefetchable for improved performance?
> > >
> > The new huge window will be prefetchable.
> 
> The DT marks it as non-prefetchable, so the kernel will now try to allocate
> space for non-prefetchable BARs from this area, which is a bug. If the second
> memory window is always prefetchable, you have to mark it accordingly in DT,
> to prevent it from being used for normal 64 bit BARs.

Forget what I wrote here, I just remembered that 64-bit BARs are by definition
prefetchable. You should still mark the range accordingly in DT for correct
operation, but it won't be used for non-prefetchable 64-bit BARs if you don't
because they do not exist.

	Arnd