linux-kernel - Re: [PATCH] pci: don't enable too much HT MSI mapping -v5 -resend

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Message-Id: <200903281431.36572.prakash@punnoor.de>
Date:	Sat, 28 Mar 2009 14:31:30 +0100
From:	Prakash Punnoor <prakash@...noor.de>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Yinghai Lu <yinghai@...nel.org>, Matthew Wilcox <matthew@....cx>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Robert Hancock <hancockrwd@...il.com>, david@...g.hm,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: don't enable too much HT MSI mapping -v5 -resend

On Samstag 28 März 2009 13:34:44 Prakash Punnoor wrote:
> On Freitag 27 März 2009 00:10:01 Jesse Barnes wrote:
> > On Fri, 20 Mar 2009 19:29:41 -0700
> >
> > Yinghai Lu <yinghai@...nel.org> wrote:
> > > Impact: fix bug
> > >
> > > Prakash reported that his c51-mcp51 system ondie sound card doesn't
> > > work MSI but if he hack out the HT-MSI on mcp51, the MSI will work
> > > well with sound card.
> > >
> > > this patch rework the nv_msi_ht_cap_quirk()
> > > and will only try to avoid to enable ht_msi on device following that
> > > root dev, and don't touch that root dev
> > >
> > > v3: will enable c51...
> > > v4: will enable c51 kind of without leaf too.
> > > v5: update to mainline
> > >
> > > Reported-by: Prakash Punnoor <prakash@...noor.de>
> > > Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> >
> > Applied, thanks.  Prakash if you get a chance can you try testing my
> > linux-next branch (or just linux-next in general tomorrow) to make sure
> > this is still ok for you?
> >
> > Thanks,
>
> Finally I am able to test the linux-next branch of pci tree after Jesse
> gave some help with git.(Is it correct that the kernel calls itself
> 2.6.28-rc8? I looked into quirks.c and it seems to be correctly patched.)
> Unfortunately it doesn't seem to work for me (and I am wondering why as the
> old v4 version seemed to work ontop of one of the 2.6.29-rc versions):
>
> dmesg|grep HT
> pci 0000:00:00.0: Found disabled HT MSI Mapping
> pci 0000:00:03.0: Enabling HT MSI Mapping
> pci 0000:00:09.0: Found disabled HT MSI Mapping
> pci 0000:00:0e.0: Enabling HT MSI Mapping
> pci 0000:00:09.0: Found disabled HT MSI Mapping
> pci 0000:00:0f.0: Enabling HT MSI Mapping
> pci 0000:00:09.0: Found disabled HT MSI Mapping
> pci 0000:00:10.0: Enabling HT MSI Mapping
> pci 0000:00:09.0: Found disabled HT MSI Mapping
> pci 0000:00:10.1: Enabling HT MSI Mapping
>
> Device 09.0 doesn't get enabled (good) but 00.0 also not (bad). Then my
> Intel HDA cannot use MSI.

I sprinkeld a few debugging messages around in the code and looking at that
I don't see how the code can enable NMSI for device 00.0, but not for 09.0:

Both will exit here:

if (host_bridge == dev && host_bridge_with_leaf(host_bridge))

in nv_ht_enable_msi_mapping, so it seems host_bridge_with_leaf returns true 
for both. I think because my hw configuration changed a bit (inserted one
PCIe card) comparing to last time I tested old v4 version, this doesn't work
anymore - so the leaf check alone is not realiable, I guess. For me adding
something like this, makes it work: (I hope the description makes sense, as
I am just refering to the function names and trying to guess its meanings.)

Patch is against linux-next branch of pci tree.

[patch] pci: enable MSI on host bridge without checking for leaves

On C51 the host bridge needs to be enabled, but the MCP51 host bridge not.
So don't check for leaves on the main host bridge.

Signed-off-by: Prakash Punnoor <prakash@...noor.de>

--- drivers/pci/quirks.c.old    2009-03-28 14:06:07.249250095 +0100
+++ drivers/pci/quirks.c        2009-03-28 14:22:35.027510230 +0100
@@ -2292,8 +2292,10 @@ static void __devinit __nv_msi_ht_cap_qu
        if (pos != 0) {
                /* Host bridge is to HT */
                if (found == 1) {
-                       /* it is not enabled, try to enable it */
-                       if (all)
+                       /* it is not enabled, try to enable it;
+                        * don't check for leaves on host bridge
+                        */
+                       if (all || host_bridge->devfn == dev->devfn)
                                ht_enable_msi_mapping(dev);
                        else
                                nv_ht_enable_msi_mapping(dev);


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