Hello Mani, On Sat, Jan 06, 2024 at 08:42:38PM +0530, Manivannan Sadhasivam wrote: > > > > So to give you a clear example: > > If you: > > 1) start the EP, start the pci-epf-test > > 2) start the RC > > 3) run pci-epf-test > > 4) reboot the RC > > > > this will trigger a link-down reset IRQ on the EP side (link_req_rst_not). > > > > Right. This is the sane RC reboot scenario. Although, there is no guarantee > that the EP will get LINK_DOWN event before perst_assert (I've seen this with > some RC platforms). > > But can you confirm whether your EP is receiving PERST assert/deassert when RC > reboots? Yes, it does: ## RC side: # reboot ## EP side [ 845.606810] pci: PERST asserted by host! [ 845.657058] pci: PCIE_CLIENT_INTR_STATUS_MISC: 0x4 [ 845.657759] pci: hot reset or link-down reset (LTSSM_STATUS: 0x0) [ 852.483985] pci: PERST de-asserted by host! [ 852.503041] pci: PERST asserted by host! [ 852.521616] pci: PCIE_CLIENT_INTR_STATUS_MISC: 0x2003 [ 852.522375] pci: link up! (LTSSM_STATUS: 0x230011) [ 852.610318] pci: PERST de-asserted by host! The time between 845 and 852 is the time it takes for the RC to boot and probe the RC PCIe driver. Note that I currently don't do anything in the perst gpio handler, I only print when receiving the PERST GPIO IRQ, as I wanted to be able to answer your question. Currently, what I do instead, in order to handle a link down (which clears all the RESBAR registers) followed by a link up, is to re-write the RESBAR registers when receiving the link down IRQ. (This is only to handle the case of the RC rebooting.) A nicer solution would probably be to modify dw_pcie_ep_set_bar() to properly handle controllers with the Resizable BAR capability, and remove the RESBAR related code from dw_pcie_ep_init_complete(). However, that would still require changes in pci-epf-test.c to call set_bar() after a hot reset/link-down reset (and it is not possible to distinguish between them), which could be done by either: 1) Making sure that the glue drivers (that implement Resizable BAR capability) call dw_pcie_ep_init_notify() when receiving a hot reset/link-down reset IRQ (or maybe instead when getting the link up IRQ), as that will trigger pci-epf-test.c to (once again) call set_bar(). or 2) Modifying pci-epf-test.c:pci_epf_test_link_up() to call set_bar() (If epc_features doesn't have a core_init_notifier, as in that case set_bar() is called by pci_epf_test_core_init()). (Since I assume that not all SoCs might have a PERST GPIO.) or 3) We could allow glue drivers that use an internal refclk to still make use of the PERST GPIO IRQ, and only call dw_pcie_ep_init_notify(), as that would also cause pci-epf-test.c to call set_bar(). (These glue drivers, which implement the Resizable BAR capability would however not need to perform a full core reset, etc. in the PERST GPIO IRQ handler, they only need to call dw_pcie_ep_init_notify().) Right now, I think I prefer 1). What do you think? Since it seems that not many SoCs that use a DWC core, have Resizable BAR capability implemented, I will try to see what I can come up with. Kind regards, Niklas
