On Thu, Sep 26, 2024 at 06:07:47PM -0400, Frank Li wrote:
> Some PCIe bridges require special handling when enabling or disabling
> PCIe devices. For example, on the i.MX95 platform, a lookup table must be
> configured to inform the hardware how to convert pci_device_id to stream
> (bus master) ID, which is used by the IOMMU and MSI controller to identify
> bus master device.
I don't think you're talking about PCI-to-PCI bridges (including PCIe
Root Ports and Switch Ports). Those are all standardized and don't do
anything with Requester IDs or Stream IDs.
A PCI host bridge, e.g., a PCIe Root Complex, might have to deal with
Stream IDs, and I think that's what you're enabling here. If so, I
think the hooks should be in struct pci_host_bridge instead of
pci_ops.
> Enablement will be failure when there is not enough lookup table resource.
> Avoid DMA write to wrong position. That is the reason why pci_fixup_enable
> can't work since not return value for fixup function.
>
> Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> ---
> drivers/pci/pci.c | 19 +++++++++++++++++++
> include/linux/pci.h | 2 ++
> 2 files changed, 21 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7d85c04fbba2a..e0f83ed53d964 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2057,6 +2057,7 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
> {
> int err;
> struct pci_dev *bridge;
> + struct pci_bus *bus;
> u16 cmd;
> u8 pin;
>
> @@ -2068,6 +2069,15 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
> if (bridge)
> pcie_aspm_powersave_config_link(bridge);
>
> + bus = dev->bus;
> + while (bus) {
> + if (bus->ops->enable_device)
> + err = bus->ops->enable_device(bus, dev);
> + if (err)
> + return err;
> + bus = bus->parent;
> + }
> +
> err = pcibios_enable_device(dev, bars);
> if (err < 0)
> return err;
> @@ -2262,12 +2272,21 @@ void pci_disable_enabled_device(struct pci_dev *dev)
> */
> void pci_disable_device(struct pci_dev *dev)
> {
> + struct pci_bus *bus;
> +
> dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0,
> "disabling already-disabled device");
>
> if (atomic_dec_return(&dev->enable_cnt) != 0)
> return;
>
> + bus = dev->bus;
> + while (bus) {
> + if (bus->ops->disable_device)
> + bus->ops->disable_device(bus, dev);
> + bus = bus->parent;
> + }
> +
> do_pci_disable_device(dev);
>
> dev->is_busmaster = 0;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 573b4c4c2be61..42c25b8efd538 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -803,6 +803,8 @@ static inline int pcibios_err_to_errno(int err)
> struct pci_ops {
> int (*add_bus)(struct pci_bus *bus);
> void (*remove_bus)(struct pci_bus *bus);
> + int (*enable_device)(struct pci_bus *bus, struct pci_dev *dev);
> + void (*disable_device)(struct pci_bus *bus, struct pci_dev *dev);
> void __iomem *(*map_bus)(struct pci_bus *bus, unsigned int devfn, int where);
> int (*read)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 *val);
> int (*write)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 val);
>
> --
> 2.34.1
>
