[PATCH v11 2/4] PCI: Factor out pci_bus_wait_crs()
From: helgaas@kernel.org (Bjorn Helgaas)
Date: 2017-08-21 19:18:10
Also in:
linux-arm-msm, linux-pci, lkml
On Mon, Aug 21, 2017 at 09:53:56AM -0400, Sinan Kaya wrote:
On 8/18/2017 5:32 PM, Bjorn Helgaas wrote:quoted
+ if ((*l & 0xffff) != 0x0001) + return true; /* not a CRS completion */This version certainly looks cleaner. However, it breaks pci_flr_wait(). If some root port doesn't support CRS and returns 0xFFFFFFFF, pci_bus_wait_crs() function returns true. pci_flr_wait() prematurely bails out from here. pci_flr_wait() { + ret = pci_bus_wait_crs(dev->bus, dev->devfn, &id, 60000); + if (ret) + return; } We can change the return code to false above but then we break pci_bus_read_dev_vendor_id() function. That's why, I was interested in creating a pci_bus_crs_visibility_supported() helper function that would check for the magic 0x0001 value and return true. Otherwise, false. pci_bus_read_dev_vendor_id() would do this pci_bus_read_dev_vendor_id() { ... if (pci_bus_crs_visibility_supported()) return pci_bus_wait_crs(dev->bus, dev->devfn, &id, 60000); return true } Similar pattern for pci_flr_wait().
I think that makes sense. We'd want to check for CRS SV being enabled, e.g., maybe read PCI_EXP_RTCTL_CRSSVE back in pci_enable_crs() and cache it somewhere. Maybe a crs_sv_enabled bit in the root port's pci_dev, and check it with something like what pcie_root_rcb_set() does?