On Tue, Aug 06, 2013 at 11:47:42PM +0800, Wei Yang wrote:
> On Tue, Aug 06, 2013 at 07:44:21AM -0600, Bjorn Helgaas wrote:
> >On Tue, Aug 06, 2013 at 02:19:24PM +0800, Wei Yang wrote:
> >> On Mon, Aug 05, 2013 at 11:58:50AM -0600, Bjorn Helgaas wrote:
> >> >[+cc Yinghai]
> >> >
> >> >On Fri, Aug 2, 2013 at 3:31 AM, Wei Yang <weiyang@xxxxxxxxxxxxxxxxxx> wrote:
> >> >> In commit 462d9303 ("PCI: Align P2P windows using pcibios_window_alignment()"),
> >> >> it introduce a new method to calculate the window alignment of P2P bridge.
> >> >>
> >> >> When the io_window_1k is set, the calculation for the io resource alignment
> >> >> is different from the original one. In the original logic before 462d9303,
> >> >> the alignment is no bigger than 4K even the io_window_1k is set. The logic
> >> >> introduced in 462d9303 will limit the alignment to 1k in this case.
> >> >>
> >> >> This patch fix this issue.
> >> >
> >> >Presumably this fixes a bug, but you don't say what it is. "different
> >> >from the original" is not a description of a problem. You need
> >> >something like "with the current code, we allocate the wrong window
> >> >size in situation X, or we allocate a window with incorrect alignment
> >> >in situation Y, etc."
> >> >
> >>
> >> With current code, we allocate the wrong window size when upstream bridge
> >> could be 1k aligned and one of the downstream port is 4k aligned.
> >>
> >> In this case, the "min_align" should be 4k. But the current code set
> >> "min_align" to 1k.
> >
>
> Hmm... sorry I should say.
>
> With current code, we allocate the wrong window size and alignment when upstream
> bridge could be 1k aligned and one of the downstream port is 4k aligned.
>
> In this case, the "min_align" should be 4k. But the current code set
> "min_align" to 1k.
Actually, I think only the alignment is wrong (not the size). But I do
agree that this looks like a problem in the current code. I'll write
this up and post the patch soon.
Bjorn
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