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

From: Guenter Roeck <linux@roeck-us.net>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
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, 07 Jul 2015 08:01:45 -0700	[thread overview]
Message-ID: <559BE9D9.4050407@roeck-us.net> (raw)
In-Reply-To: <20150707144019.GH4379@red-moon>

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 ?

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.

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.

Thanks,
Guenter