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.
>
> Here is an example for this case.
>
> Assume:
> 1. pcibios_window_alignment() return 1.
> 2. window_alignment() return PCI_P2P_DEFAULT_IO_ALIGN_1K.
> 3. one of the child device has an IO resource with size of 2K.
>
> Result comparison:
>
> Before 462d9303 After 462d9303
> min_align 1k 1k
> |
> after loop |
> V
> min_align 2k 2k
> |
> check boundary |
> V
> min_align 2k 1k
>
> After applying the change:
>
> Result comparison:
>
> with 462d9303 with this patch
> min_align 1k 1k
> io_align 1k 4k
> |
> after loop |
> V
> min_align 2k 2k
> io_align 1k 4k
> |
> check boundary |
> V
> min_align 1k 2k
> io_align 1k 1k
>
> Signed-off-by: Wei Yang <weiyang@xxxxxxxxxxxxxxxxxx>
Gavin, can you ack this, since you wrote the original commit involved?
> ---
> drivers/pci/setup-bus.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index d4f1ad9..6c111e9 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -755,6 +755,10 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size,
> return;
>
> io_align = min_align = window_alignment(bus, IORESOURCE_IO);
> + /* Don't exceed 4KiB for windows requesting 1KiB alignment */
> + if (bus->self->io_window_1k && io_align == PCI_P2P_DEFAULT_IO_ALIGN_1K)
> + io_align = PCI_P2P_DEFAULT_IO_ALIGN;
> +
> list_for_each_entry(dev, &bus->devices, bus_list) {
> int i;
>
> --
> 1.7.5.4
>
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