linux-kernel - Re: [PATCH -v2 01/16] PCI: add declaration for pcibios_set

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Message-ID: <1323117157.660.22.camel@pasglop>
Date:	Tue, 06 Dec 2011 07:32:37 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Myron Stowe <myron.stowe@...hat.com>, linux-pci@...r.kernel.org,
	linux@....linux.org.uk, vapier@...too.org, dhowells@...hat.com,
	ysato@...rs.sourceforge.jp, tony.luck@...el.com,
	fenghua.yu@...el.com, monstr@...str.eu, ralf@...ux-mips.org,
	paulus@...ba.org, lethal@...ux-sh.org, davem@...emloft.net,
	cmetcalf@...era.com, gxt@...c.pku.edu.cn, tglx@...utronix.de,
	mingo@...hat.com, chris@...kel.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -v2 01/16] PCI: add declaration for pcibios_set_master()
 to pci core

On Mon, 2011-12-05 at 11:06 -0800, Jesse Barnes wrote:
> On Fri, 28 Oct 2011 15:47:35 -0600
> Myron Stowe <myron.stowe@...hat.com> wrote:
> 
> > From: Myron Stowe <mstowe@...hat.com>
> > 
> > Currently, pcibios_set_master() is implemented in architecture-
> > specific code.  There is nothing architecture-specific about PCI's
> > 'latency timer'.
> > 
> > This patch adds a declaration for pcibios_set_master() to PCI's core
> > in preperation for pulling the function itself up into the core.
> > Without the addition of this declaration, subsequent patches that
> > remove inline definitions of pcibios_set_master() would be removing
> > the only declaration of such.
> > 
> > No functional change.
> > 
> > Signed-off-by: Myron Stowe <myron.stowe@...hat.com>
> > ---
> 
> Ok this series is in -next.  Let's see what breaks this time. :)

On the other hand...

One thing that annoys the sh*it out of me is that I cannot use
pcibios_set_master() to establish the DMA/iommu resources for a device,
because set_dma_mask() will be called -after- set_master(), thus I need
to provision every device with 32-bit DMA resources (which can be quite
scarse) just in case the driver doesn't later call set_dma_mask(64-bit).

If only we could reverse the call order... lots of drivers to fix
unfortunately.

In which case I -would- hook into pcibios_set_master()...

Cheers,
Ben.


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