On Wed, Apr 03, 2024 at 10:03:26PM +0200, Niklas Cassel wrote: > On Wed, Apr 03, 2024 at 07:02:17PM +0530, Manivannan Sadhasivam wrote: > > On Tue, Apr 02, 2024 at 01:18:54PM +0200, Niklas Cassel wrote: > > > On Mon, Apr 01, 2024 at 09:20:36PM +0530, Manivannan Sadhasivam wrote: > > > > PCIe host controller drivers are supposed to properly reset the endpoint > > > > devices during host shutdown/reboot. Currently, Qcom driver doesn't do > > > > anything during host shutdown/reboot, resulting in both PERST# and refclk > > > > getting disabled at the same time. This prevents the endpoint device > > > > firmware to properly reset the state machine. Because, if the refclk is > > > > cutoff immediately along with PERST#, access to device specific registers > > > > within the endpoint will result in a firmware crash. > > > > > > > > To address this issue, let's call qcom_pcie_host_deinit() inside the > > > > shutdown callback, that asserts PERST# and then cuts off the refclk with a > > > > delay of 1ms, thus allowing the endpoint device firmware to properly > > > > cleanup the state machine. > ... > For a real PCIe card, if you assert + msleep(100) + deassert PERST, surely > the endpoint is supposed to be in a good/well defined state, regardless if > he REFCLK was cutoff at the exact time as PERST was asserted or not? I think this is the key point. This PERST#/REFCLK timing requirement seems like a defect in the endpoint. I know there's firmware involved and whatnot, but IMO it's the endpoint's problem to handle these issues internally. Bjorn
