Re: [PATCH v3] PCI: Only enable IO window if supported

[Guenter Roeck]

On 08/06/2015 04:32 PM, Yinghai Lu wrote:
> On Thu, Aug 6, 2015 at 9:18 AM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> > On 08/06/2015 08:58 AM, Yinghai Lu wrote:
>
> > Ok, I admit that I am lost. Earlier it seemed that you were concerned about
> > this case, where no io window is available or a bus doesn't support io,
> > but a non-transparent child does. Now you seem to say that the
> > non-transparent
> > child would not be able to support IO either.
> >
> > For my education, can you list the possible options, and how you suggest
> > to solve them ? I can see the following situations.
> >
> > - root supports IO, but has no io window assigned
> > - root does not support IO and has or has not an IO window assigned
> > - a bridge does not support IO
>
> should have two cases:
> 1. root bus does not have io window exposed.
> 2. pci bridge io bar is not writable.
>
> > For the transparent case, each of those should result in all children
> > not even trying to assign an IO window, which is what we want,
> > and what my patc set tries to do.
> >
> > How should those cases be handled for non-transparent bridges ?
>
> for case 2: current upstream code, no warning for the bridge itself,
> but have warning for devices under the bridge.

That warning is what I am trying to get rid of, because it is repeated
dozens of times with zero value.

> We only need to handle case 1, aka root bus does not have io port window.
>
> What about your setup, is it case 1 or case 2?

Assuming case 1) includes case 3), root bridge does not support IO,
I have both case 1 and 2.

Anyway, I think I am giving up. Sorry, I just fail to understand the
use case(s) you are trying to cover.

Why don't you submit a patch, I'll test it if it works for my use
case, and if it works we ask Bjorn to apply it. My problem is quite
simple: I don't want to get flooded with useless "no IO window" messages.
How it is solved doesn't matter to me, as long as it is solved.
Since you have a strong opinion on how it should be solved, we should
go with your solution and not keep turning in circles forever.

Thanks
Guenter

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