On Thu, Jun 06, 2024 at 12:56:36PM +0530, Manivannan Sadhasivam wrote:

As per the PCIe base spec r5.0, section 5.2, Link Down event can happen
under any of the following circumstances:

1. Fundamental/Hot reset
2. Link disable transmission by upstream component
3. Moving from L2/L3 to L0

In those cases, Link Down causes some non-sticky DWC registers to loose the
state (like REBAR, etc...). So the drivers need to reinitialize them to
function properly once the link comes back again.

This is not a problem for drivers supporting PERST# IRQ, since they can
reinitialize the registers in the PERST# IRQ callback. But for the drivers
not supporting PERST#, there is no way they can reinitialize the registers
other than relying on Link Down IRQ received when the link goes down. So
let's add a DWC generic API dw_pcie_ep_linkdown() that reinitializes the
non-sticky registers and also notifies the EPF drivers about link going
down.

This API can also be used by the drivers supporting PERST# to handle the
scenario (2) mentioned above.

NOTE: For the sake of code organization, move the dw_pcie_ep_linkup()
definition just above dw_pcie_ep_linkdown().

Reviewed-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <redacted>

This patch already seems to be present in linux-next:
https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?id=3d2e425263e2674713220379ad04e925efdb731d&h=next

Other patches in this series also seem to be merged.

[...]

Regards,
Siddharth.