On Tuesday 20 July 2021 13:50:08 Nirmal Patel wrote:
> During VT-d passthrough repetitive reboot tests, it was determined that the VMD
> domain needed to be reset in order to allow downstream devices to reinitialize
> properly. This is done using a secondary bus reset at each of the VMD root
> ports and any bridges in the domain.
>
> Signed-off-by: Nirmal Patel <nirmal.patel@xxxxxxxxxxxxxxx>
> Reviewed-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> ---
> drivers/pci/controller/vmd.c | 46 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 46 insertions(+)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index e3fcdfec58b3..6e1c60048774 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -15,6 +15,7 @@
> #include <linux/srcu.h>
> #include <linux/rculist.h>
> #include <linux/rcupdate.h>
> +#include <linux/delay.h>
>
> #include <asm/irqdomain.h>
> #include <asm/device.h>
> @@ -447,6 +448,49 @@ static struct pci_ops vmd_ops = {
> .write = vmd_pci_write,
> };
>
> +#define PCI_HEADER_TYPE_MASK 0x7f
> +#define PCI_CLASS_BRIDGE_PCI 0x0604
> +#define DEVICE_SPACE (8 * 4096)
> +#define VMD_DEVICE_BASE(vmd, device) ((vmd)->cfgbar + (device) * DEVICE_SPACE)
> +#define VMD_FUNCTION_BASE(vmd, device, fn) ((vmd)->cfgbar + (device) * (DEVICE_SPACE + (fn*4096)))
> +static void vmd_domain_sbr(struct vmd_dev *vmd)
> +{
> + char __iomem *base;
> + u16 ctl;
> + int dev_seq;
> + int max_devs = resource_size(&vmd->resources[0]) * 32;
> +
> + /*
> + * Subdevice config space may or many not be mapped linearly using 4k config
> + * space.
> + */
> + for (dev_seq = 0; dev_seq < max_devs; dev_seq++) {
> + base = VMD_DEVICE_BASE(vmd, dev_seq);
> + if (readw(base + PCI_VENDOR_ID) != PCI_VENDOR_ID_INTEL)
> + continue;
> +
> + if ((readb(base + PCI_HEADER_TYPE) & PCI_HEADER_TYPE_MASK) !=
> + PCI_HEADER_TYPE_BRIDGE)
> + continue;
> +
> + if (readw(base + PCI_CLASS_DEVICE) != PCI_CLASS_BRIDGE_PCI)
> + continue;
> +
> + /* pci_reset_secondary_bus() */
> + ctl = readw(base + PCI_BRIDGE_CONTROL);
> + ctl |= PCI_BRIDGE_CTL_BUS_RESET;
> + writew(ctl, base + PCI_BRIDGE_CONTROL);
> + readw(base + PCI_BRIDGE_CONTROL);
> + msleep(2);
> +
> + ctl &= ~PCI_BRIDGE_CTL_BUS_RESET;
> + writew(ctl, base + PCI_BRIDGE_CONTROL);
> + readw(base + PCI_BRIDGE_CONTROL);
Hello!
You cannot unconditionally call secondary bus reset for arbitrary PCIe
Bridge. Calling it breaks more PCIe devices behind bridge and
pci_reset_secondary_bus() already handles it and skip reset if reset is
causing issues.
I would suggest to use pci_reset_secondary_bus() and extend it
so you can call it also from your driver.
> + }
> + ssleep(1);
> +}
> +
> static void vmd_attach_resources(struct vmd_dev *vmd)
> {
> vmd->dev->resource[VMD_MEMBAR1].child = &vmd->resources[1];
> @@ -747,6 +791,8 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
> if (vmd->irq_domain)
> dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
>
> + vmd_domain_sbr(vmd);
> +
> pci_scan_child_bus(vmd->bus);
> pci_assign_unassigned_bus_resources(vmd->bus);
>
> --
> 2.27.0
>
