Re: [PATCH] PCI: Only enable IO window if supported

From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
	Will Deacon <Will.Deacon@arm.com>
Subject: Re: [PATCH] PCI: Only enable IO window if supported
Date: Tue, 7 Jul 2015 18:28:19 +0100	[thread overview]
Message-ID: <20150707172818.GA930@red-moon> (raw)
In-Reply-To: <559BE9D9.4050407@roeck-us.net>

On Tue, Jul 07, 2015 at 04:01:45PM +0100, Guenter Roeck wrote:
> Hi Lorenzo,
> 
> On 07/07/2015 07:40 AM, Lorenzo Pieralisi wrote:
> > On Fri, Jun 19, 2015 at 05:24:13PM +0100, Lorenzo Pieralisi wrote:
> >> Hi Guenter,
> >>
> >> On Thu, Jun 18, 2015 at 07:01:03PM +0100, Guenter Roeck wrote:
> >>> On Thu, May 28, 2015 at 07:41:12AM -0500, Bjorn Helgaas wrote:
> >>>>
> >>>>>> I'd like res->flags to reflect the capabilities of the hardware, not
> >>>>>> whether the window is currently enabled.
> >>>>>>
> >>>>> Flag bits seem to be all taken. Could we use IORESOURCE_DISABLED for that
> >>>>> purpose, or could that cause conflicts elsewhere ?
> >>>>
> >>>> Yes, I think IORESOURCE_DISABLED would be appropriate for any I/O windows
> >>>> below a host bridge that doesn't support I/O space.
> >>>>
> >>> I integrated Lorenzo's patch and tried to get this working.
> >>
> >> Thanks. How do you want to proceed with this ? Are you taking my patch
> >> and post it along with your updated series ? We need to extend test
> >> coverage to platforms we could not test on, as you know my series
> >> affects all archs but SPARC (I mean it should *not* affect them, this
> >> has to be tested though, I do not have the HW needed, your coverage
> >> for x86 and PowerPC is great but I do not think it can be deemed
> >> sufficient).
> >>
> >> Please let me know, thanks !
> >
> > Any comment on this ? I will have to remove the bridge resource claiming
> > from my patch according to Ben's concerns for PowerPC, which requires
> > a v3.
> >
> > How do you want me to go on with this ?
> >
> 
> Can you send your v3 ?

Yes, I have to figure out though where I can claim bridge resources
on PROBE_ONLY arm/arm64 systems, which is proving interesting, anyway
I will send it out asap.

> I didn't submit my latest version because I recalled Ben's objections,
> and I never got around asking you if you plan to send a new version
> of your patch.

No worries, let's get this sorted.

> I had to drop the idea of using IORESOURCE_DISABLED; pretty much all
> kernel code uses the "!flags" test to identify unused resources.
> I tried to change that, but just could not get it to work.
> I ended up introducing a new bus flag instead, PCI_BUS_FLAGS_NO_IO,
> which works quite nicely since it propagates to child buses.

Ok, great, I can test it too.

Thanks,
Lorenzo