Hi Frank, On Tue, Aug 20, 2024 at 08:52:41AM +0200, Stefan Eichenberger wrote: > On Mon, Aug 19, 2024 at 10:30:38AM -0400, Frank Li wrote: > > On Mon, Aug 19, 2024 at 11:03:16AM +0200, Stefan Eichenberger wrote: > > > On the i.MX6Quad (not QuadPlus), the PCIe link does not work after a > > > suspend/resume cycle. Worse, the PCIe memory mapped I/O isn't accessible > > > at all, so the system freezes when a PCIe driver tries to access its I/O > > > space. The only way to get resume working again is to reset the PCIe > > > link, similar to what is done on devices that support suspend/resume. > > > Through trial and error, we found that something about the PCIe > > > reference clock does not work as expected after a resume. We could not > > > figure out if it is disabled (even though the registers still say it is > > > enabled), or if it is somehow unstable or has some hiccups. With the > > > workaround introduced in this patch series, we were able to fully resume > > > a Compex WLE900VX (ath10k) miniPCIe Wifi module and an Intel AX200 M.2 > > > Wifi module. If there is a better way or other ideas on how to fix this > > > problem, please let us know. We are aware that resetting the link should > > > not be necessary, but we could not find a better solution. More > > > interestingly, even the SoCs that support suspend/resume according to > > > the i.MX erratas seem to reset the link on resume in > > > imx6_pcie_host_init, so we hope this might be a valid workaround. > > > > > > Stefan Eichenberger (3): > > > PCI: imx6: Add a function to deassert the reset gpio > > > PCI: imx6: move the wait for clock stabilization to enable ref clk > > > PCI: imx6: reset link on resume > > > > Thanks you for your patch, but it may have conflict with > > https://lore.kernel.org/linux-pci/Zr4XG6r+HnbIlu8S@lizhi-Precision-Tower-5810/T/#t > > > > Thanks a lot for the hint. I will have a look at the series and see if I > can adapt my changes including your suggestions. I did some more tests with your series applied. Everything works as expected on an i.MX8M Plus. However, the i.MX6Quad PCIe link still does not work after a resume. I could trace the issues back to the following functions, besides that we could use the same suspend/resume function as for the other i.MX SoCs. In suspend the follwoing function is causing issues: imx_pcie_stop_link(imx_pcie->pci); In resume the following functions are causing issues: imx_pcie->drvdata->init_phy(imx_pcie); // in imx_pcie_host_init imx_pcie_start_link(imx_pcie->pci); I think the second one makes sense because I could not stop the link I should not start it again. But why is also the init_phy function failing? Are they required to setup the link? The messages I get when the system resumes are: [ 50.176212] Enabling non-boot CPUs ... [ 50.194446] CPU1 is up [ 50.198087] CPU2 is up [ 50.201746] CPU3 is up [ 50.563710] imx6q-pcie 1ffc000.pcie: Read DBI address failed After the last message the system hangs. It seems this happens because the PCIe I/O mem is not accessible anymore. Do you have an idea what could cause imx_pcie_stop_link to break the link on resume? Without calling them the link is working fine after resuming and the drivers can access the PCIe I/O mem. Thanks, Stefan
