Re: [PATCH] PCI: Enable io space 1k granularity for intel cpu root port

Bjorn Helgaas
2024-06-21T21:02:10Z

On Fri, Jun 21, 2024 at 02:06:08AM +0000, Zhou Shengqing wrote:
> This patch add 1k granularity for intel root port bridge.Intel latest
> server CPU support 1K granularity,And there is an BIOS setup item named
> "EN1K",but linux doesn't support it. if an IIO has 5 IOU (SPR has 5 IOUs)
> all are bifurcated 2x8.In a 2P server system,There are 20 P2P bridges
> present.if keep 4K granularity allocation,it need 20*4=80k io space,
> exceeding 64k.I test it in a 16*nvidia 4090s system under intel eaglestrem
> platform.There are six 4090s that cannot be allocated I/O resources.
> So I applied this patch.And I found a similar implementation in quirks.c,
> but it only targets the Intel P64H2 platform.
>
> Signed-off-by: Zhou Shengqing <zhoushengqing@ttyinfo.com>
> ---
> drivers/pci/probe.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 5fbabb4e3425..3f0c901c6653 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -461,6 +461,8 @@ static void pci_read_bridge_windows(struct pci_dev *bridge)
> u32 buses;
> u16 io;
> u32 pmem, tmp;
> + u16 ven_id, dev_id;
> + u16 en1k = 0;
> struct resource res;
>
> pci_read_config_dword(bridge, PCI_PRIMARY_BUS, &buses);
> @@ -478,6 +480,26 @@ static void pci_read_bridge_windows(struct pci_dev *bridge)
> }
> if (io) {
> bridge->io_window = 1;
> + if (pci_is_root_bus(bridge->bus)) {
> + list_for_each_entry(dev, &bridge->bus->devices, bus_list) {
> + pci_read_config_word(dev, PCI_VENDOR_ID, &ven_id);
> + pci_read_config_word(dev, PCI_DEVICE_ID, &dev_id);
> + if (ven_id == PCI_VENDOR_ID_INTEL && dev_id == 0x09a2) {
> + /*IIO MISC Control offset 0x1c0*/
> + pci_read_config_word(dev, 0x1c0, &en1k);
> + }
> + }
> + /*
> + *Intel ICX SPR EMR GNR
> + *IIO MISC Control (IIOMISCCTRL_1_5_0_CFG) — Offset 1C0h
> + *bit 2:Enable 1K (EN1K)
> + *This bit when set, enables 1K granularity for I/O space decode
> + *in each of the virtual P2P bridges
> + *corresponding to root ports, and DMI ports.
> + */
> + if (en1k & 0x4)
> + bridge->io_window_1k = 1;
> + }

Can you implement this as a quirk similar to quirk_p64h2_1k_io()?

I don't want to clutter the generic code with device-specific things
like this.

> pci_read_bridge_io(bridge, &res, true);
> }
>
> --
> 2.39.2
>