Re: [PATCH v3 1/2] PCI: Add enable_device() and disable_device() callbacks for bridges

Bjorn Helgaas
2024-10-30T21:02:50Z

On Thu, Oct 24, 2024 at 06:34:44PM -0400, Frank Li wrote:
> Some PCIe host bridges require special handling when enabling or disabling
> PCIe Endpoints. For example, the i.MX95 platform has a lookup table to map
> Requester IDs to StreamIDs, which are used by the SMMU and MSI controller
> to identify the source of DMA accesses.
>
> Without this mapping, DMA accesses may target unintended memory, which
> would corrupt memory or read the wrong data.
>
> Add a host bridge .enable_device() hook the imx6 driver can use to
> configure the Requester ID to StreamID mapping. The hardware table isn't
> big enough to map all possible Requester IDs, so this hook may fail if no
> table space is available. In that case, return failure from
> pci_enable_device().
>
> It might make more sense to make pci_set_master() decline to enable bus
> mastering and return failure, but it currently doesn't have a way to return
> failure.
>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

Merge along with the imx6 change.

> ---
> Change from v2 to v3
> - use Bjorn suggest's commit message.
> - call disable_device() when error happen.
>
> Change from v1 to v2
> - move enable(disable)device ops to pci_host_bridge
> ---
> drivers/pci/pci.c | 23 ++++++++++++++++++++++-
> include/linux/pci.h | 2 ++
> 2 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7d85c04fbba2a..5e0cb9b6f4d4f 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2056,6 +2056,7 @@ int __weak pcibios_enable_device(struct pci_dev *dev, int bars)
> static int do_pci_enable_device(struct pci_dev *dev, int bars)
> {
> int err;
> + struct pci_host_bridge *host_bridge;
> struct pci_dev *bridge;
> u16 cmd;
> u8 pin;
> @@ -2068,9 +2069,16 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
> if (bridge)
> pcie_aspm_powersave_config_link(bridge);
>
> + host_bridge = pci_find_host_bridge(dev->bus);
> + if (host_bridge && host_bridge->enable_device) {
> + err = host_bridge->enable_device(host_bridge, dev);
> + if (err)
> + return err;
> + }
> +
> err = pcibios_enable_device(dev, bars);
> if (err < 0)
> - return err;
> + goto err_enable;
> pci_fixup_device(pci_fixup_enable, dev);
>
> if (dev->msi_enabled || dev->msix_enabled)
> @@ -2085,6 +2093,13 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
> }
>
> return 0;
> +
> +err_enable:
> + if (host_bridge && host_bridge->disable_device)
> + host_bridge->disable_device(host_bridge, dev);
> +
> + return err;
> +
> }
>
> /**
> @@ -2262,12 +2277,18 @@ void pci_disable_enabled_device(struct pci_dev *dev)
> */
> void pci_disable_device(struct pci_dev *dev)
> {
> + struct pci_host_bridge *host_bridge;
> +
> dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0,
> "disabling already-disabled device");
>
> if (atomic_dec_return(&dev->enable_cnt) != 0)
> return;
>
> + host_bridge = pci_find_host_bridge(dev->bus);
> + if (host_bridge && host_bridge->disable_device)
> + host_bridge->disable_device(host_bridge, dev);
> +
> do_pci_disable_device(dev);
>
> dev->is_busmaster = 0;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 573b4c4c2be61..ac15b02e14ddd 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -578,6 +578,8 @@ struct pci_host_bridge {
> u8 (*swizzle_irq)(struct pci_dev *, u8 *); /* Platform IRQ swizzler */
> int (*map_irq)(const struct pci_dev *, u8, u8);
> void (*release_fn)(struct pci_host_bridge *);
> + int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
> + void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
> void *release_data;
> unsigned int ignore_reset_delay:1; /* For entire hierarchy */
> unsigned int no_ext_tags:1; /* No Extended Tags */
>
> --
> 2.34.1
>