Re: [PATCH 07/11] PCI: dwc: ep: Add a generic dw_pcie_ep_linkdown() API to handle Link Down event

[Niklas Cassel <cassel@kernel.org>]

On Thu, Mar 14, 2024 at 08:53:46PM +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().
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> ---

Reviewed-by: Niklas Cassel <cassel@kernel.org>