Re: [PATCH v7 0/4] PCI: Add support for resetting the Root Ports in a platform specific way

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

On 3/10/2026 7:31 PM, Manivannan Sadhasivam via B4 Relay wrote:
> Hi,
>
> Currently, in the event of AER/DPC, PCI core will try to reset the slot (Root
> Port) and its subordinate devices by invoking bridge control reset and FLR. But
> in some cases like AER Fatal error, it might be necessary to reset the Root
> Ports using the PCI host bridge drivers in a platform specific way (as indicated
> by the TODO in the pcie_do_recovery() function in drivers/pci/pcie/err.c).
> Otherwise, the PCI link won't be recovered successfully.
>
> So this series adds a new callback 'pci_host_bridge::reset_root_port' for the
> host bridge drivers to reset the Root Port when a fatal error happens.
>
> Also, this series allows the host bridge drivers to handle PCI link down event
> by resetting the Root Ports and recovering the bus. This is accomplished by the
> help of the new 'pci_host_handle_link_down()' API. Host bridge drivers are
> expected to call this API (preferrably from a threaded IRQ handler) with
> relevant Root Port 'pci_dev' when a link down event is detected for the port.
> The API will reuse the pcie_do_recovery() function to recover the link if AER
> support is enabled, otherwise it will directly call the reset_root_port()
> callback of the host bridge driver (if exists).
>
> For reference, I've modified the pcie-qcom driver to call
> pci_host_handle_link_down() API with Root Port 'pci_dev' after receiving the
> LDn global_irq event and populated 'pci_host_bridge::reset_root_port()'
> callback to reset the Root Ports.
>   
> Testing
> -------
>
> Tested on Qcom Lemans AU Ride platform with Host and EP SoCs connected over PCIe
> link. Simulated the LDn by disabling LTSSM_EN on the EP and I could verify that
> the link was getting recovered successfully.
>
> Changes in v7:
> - Dropped Rockchip Root port reset patch due to reported issues. But the series
>    works on other platforms as tested by others.
> - Added pci_{lock/unlock}_rescan_remove() to guard pci_bus_error_reset() as the
>    device could be removed in-between due to Native hotplug interrupt.
> - Rebased on top of v7.0-rc1
> - Link to v6: https://lore.kernel.org/r/20250715-pci-port-reset-v6-0-6f9cce94e7bb@oss.qualcomm.com
>
> Changes in v6:
> - Incorporated the patch: https://lore.kernel.org/all/20250524185304.26698-2-manivannan.sadhasivam@linaro.org/
> - Link to v5: https://lore.kernel.org/r/20250715-pci-port-reset-v5-0-26a5d278db40@oss.qualcomm.com
>
> Changes in v5:
> * Reworked the pci_host_handle_link_down() to accept Root Port instead of
>    resetting all Root Ports in the event of link down.
> * Renamed 'reset_slot' to 'reset_root_port' to avoid confusion as both terms
>    were used interchangibly and the series is intended to reset Root Port only.
> * Added the Rockchip driver change to this series.
> * Dropped the applied patches and review/tested tags due to rework.
> * Rebased on top of v6.16-rc1.
>
> Changes in v4:
> - Handled link down first in the irq handler
> - Updated ICC & OPP bandwidth after link up in reset_slot() callback
> - Link to v3: https://lore.kernel.org/r/20250417-pcie-reset-slot-v3-0-59a10811c962@linaro.org
>
> Changes in v3:
> - Made the pci-host-common driver as a common library for host controller
>    drivers
> - Moved the reset slot code to pci-host-common library
> - Link to v2: https://lore.kernel.org/r/20250416-pcie-reset-slot-v2-0-efe76b278c10@linaro.org
>
> Changes in v2:
> - Moved calling reset_slot() callback from pcie_do_recovery() to pcibios_reset_secondary_bus()
> - Link to v1: https://lore.kernel.org/r/20250404-pcie-reset-slot-v1-0-98952918bf90@linaro.org
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
For entire series,
Reviewed-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>

- Krishna Chaitanya.
> ---
> Manivannan Sadhasivam (4):
>        PCI/ERR: Add support for resetting the Root Ports in a platform specific way
>        PCI: host-common: Add link down handling for Root Ports
>        PCI: qcom: Add support for resetting the Root Port due to link down event
>        misc: pci_endpoint_test: Add AER error handlers
>
>   drivers/misc/pci_endpoint_test.c         |  20 +++++
>   drivers/pci/controller/dwc/pcie-qcom.c   | 143 ++++++++++++++++++++++++++++++-
>   drivers/pci/controller/pci-host-common.c |  35 ++++++++
>   drivers/pci/controller/pci-host-common.h |   1 +
>   drivers/pci/pci.c                        |  21 +++++
>   drivers/pci/pcie/err.c                   |   6 +-
>   include/linux/pci.h                      |   1 +
>   7 files changed, 221 insertions(+), 6 deletions(-)
> ---
> base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
> change-id: 20250715-pci-port-reset-4d9519570123
>
> Best regards,