On 3 July 2017 at 00:18, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > On Tue, Jun 20, 2017 at 10:17:40AM +0200, Marc Gonzalez wrote: >> This driver is required to work around several hardware bugs >> in the PCIe controller. >> >> NB: Revision 1 does not support legacy interrupts, or IO space. > > I had to apply these manually because of conflicts in Kconfig and > Makefile. What are these based on? Easiest for me is if you base > them on the current -rc1 tag. > >> Signed-off-by: Marc Gonzalez <marc_gonzalez@xxxxxxxxxxxxxxxx> >> --- >> drivers/pci/host/Kconfig | 8 +++ >> drivers/pci/host/Makefile | 1 + >> drivers/pci/host/pcie-tango.c | 164 ++++++++++++++++++++++++++++++++++++++++++ >> include/linux/pci_ids.h | 2 + >> 4 files changed, 175 insertions(+) >> create mode 100644 drivers/pci/host/pcie-tango.c >> [..] >> + /* >> + * QUIRK #2 >> + * Unfortunately, config and mem spaces are muxed. >> + * Linux does not support such a setting, since drivers are free >> + * to access mem space directly, at any time. >> + * Therefore, we can only PRAY that config and mem space accesses >> + * NEVER occur concurrently. >> + */ >> + writel_relaxed(1, pcie->mux); >> + ret = pci_generic_config_read(bus, devfn, where, size, val); >> + writel_relaxed(0, pcie->mux); > > I'm very hesitant about this. When people stress this, we're going to > get reports of data corruption. Even with the disclaimer below, I > don't feel good about this. Adding the driver is an implicit claim > that we support the device, but we know it can't be made reliable. > I noticed that the Synopsys driver suffers from a similar issue: in dw_pcie_rd_other_conf(), it happily reprograms the outbound I/O window to perform a config space access, and switches it back to I/O space afterwards (unless it has more than 2 viewports, in which case it uses dedicated windows for I/O space and config space)
