Re: [PATCH v7 1/2] PCI: Add enable_device() and disable_device() callbacks for bridges

Lorenzo Pieralisi
2024-12-05T10:32:03Z

On Tue, Dec 03, 2024 at 06:27:15PM -0500, 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.
>
> Reviewed-by: Marc Zyngier <maz@kernel.org>
> Tested-by: Marc Zyngier <maz@kernel.org>
> Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> Change from v5 to v6
> - Add Marc testedby and Reviewed-by tag
> - Add Mani's acked tag
>
> Change from v4 to v5
> - Add two static help functions
> int pci_host_bridge_enable_device(dev);
> void pci_host_bridge_disable_device(dev);
> - remove tags because big change
> Acked-by: Bjorn Helgaas <bhelgaas@google.com>

I can pick it up when Bjorn acks it.

> Reviewed-by: Marc Zyngier <maz@kernel.org>
> Tested-by: Marc Zyngier <maz@kernel.org>
>
> Change from v3 to v4
> - Add Bjorn's ack tag
>
> 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 | 36 +++++++++++++++++++++++++++++++++++-
> include/linux/pci.h | 2 ++
> 2 files changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 0b29ec6e8e5e2..773ca3cbd3221 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2059,6 +2059,28 @@ int __weak pcibios_enable_device(struct pci_dev *dev, int bars)
> return pci_enable_resources(dev, bars);
> }
>
> +static int pci_host_bridge_enable_device(struct pci_dev *dev)
> +{
> + struct pci_host_bridge *host_bridge = pci_find_host_bridge(dev->bus);
> + int err;
> +
> + if (host_bridge && host_bridge->enable_device) {
> + err = host_bridge->enable_device(host_bridge, dev);
> + if (err)
> + return err;
> + }
> +
> + return 0;
> +}
> +
> +static void pci_host_bridge_disable_device(struct pci_dev *dev)
> +{
> + struct pci_host_bridge *host_bridge = pci_find_host_bridge(dev->bus);
> +
> + if (host_bridge && host_bridge->disable_device)
> + host_bridge->disable_device(host_bridge, dev);
> +}
> +
> static int do_pci_enable_device(struct pci_dev *dev, int bars)
> {
> int err;
> @@ -2074,9 +2096,13 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
> if (bridge)
> pcie_aspm_powersave_config_link(bridge);
>
> + err = pci_host_bridge_enable_device(dev);
> + if (err)
> + return err;
> +
> err = pcibios_enable_device(dev, bars);

Next in line is removing pcibios_enable_device() arch callbacks and move
that code into bridge callbacks to do the same, we can do it later.

Lorenzo

> if (err < 0)
> - return err;
> + goto err_enable;
> pci_fixup_device(pci_fixup_enable, dev);
>
> if (dev->msi_enabled || dev->msix_enabled)
> @@ -2091,6 +2117,12 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
> }
>
> return 0;
> +
> +err_enable:
> + pci_host_bridge_disable_device(dev);
> +
> + return err;
> +
> }
>
> /**
> @@ -2274,6 +2306,8 @@ void pci_disable_device(struct pci_dev *dev)
> if (atomic_dec_return(&dev->enable_cnt) != 0)
> return;
>
> + pci_host_bridge_disable_device(dev);
> +
> do_pci_disable_device(dev);
>
> dev->is_busmaster = 0;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index db9b47ce3eefd..bcbef004dd561 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -595,6 +595,8 @@ 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
>