On Tue, Aug 06, 2013 at 12:01:55PM -0600, Bjorn Helgaas wrote:
> 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.
Here's the patch I propose. The code change is the same as I posted
yesterday; only the changelog is new. I'll put these in next pending
comments.
Bjorn
commit 2d1d66780ecd12c9518835303f5302fc5262d49b
Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Date: Mon Aug 5 16:15:10 2013 -0600
PCI: Align bridge I/O windows as required by downstream devices & bridges
An upstream bridge's I/O window must be at least as aligned as any
downstream device or bridge requires. In particular, if the upstream
bridge supports 1K alignment but a downstream bridge requires 4K alignment,
the upstream window must also be 4K aligned.
Therefore, do not reduce the required alignment ("min_align") based on
the upstream bridge's capabilities.
Reported-by: Wei Yang <weiyang@xxxxxxxxxxxxxxxxxx>
Suggested-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index d4f1ad9..8333c92 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -749,12 +749,12 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO);
resource_size_t size = 0, size0 = 0, size1 = 0;
resource_size_t children_add_size = 0;
- resource_size_t min_align, io_align, align;
+ resource_size_t min_align, align;
if (!b_res)
return;
- io_align = min_align = window_alignment(bus, IORESOURCE_IO);
+ min_align = window_alignment(bus, IORESOURCE_IO);
list_for_each_entry(dev, &bus->devices, bus_list) {
int i;
@@ -781,9 +781,6 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
}
}
- if (min_align > io_align)
- min_align = io_align;
-
size0 = calculate_iosize(size, min_size, size1,
resource_size(b_res), min_align);
if (children_add_size > add_size)
--
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