On Thu, Apr 20, 2017 at 04:31:25PM +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.
>
> Signed-off-by: Marc Gonzalez <marc_gonza...@sigmadesigns.com>
> ---
> Documentation/devicetree/bindings/pci/tango-pcie.txt | 32 ++++++++
> drivers/pci/host/Kconfig | 8 ++
> drivers/pci/host/Makefile | 1 +
> drivers/pci/host/pcie-tango.c | 161
> +++++++++++++++++++++++++++++++++++++++
> include/linux/pci_ids.h | 2 +
> 5 files changed, 204 insertions(+)
> ...
> +static int smp8759_config_read(struct pci_bus *bus,
> + unsigned int devfn, int where, int size, u32 *val)
> +{
> + int ret;
> + struct pci_config_window *cfg = bus->sysdata;
> + struct tango_pcie *pcie = dev_get_drvdata(cfg->parent);
> +
> + /*
> + * QUIRK #1
> + * Reads in configuration space outside devfn 0 return garbage.
> + */
> + if (devfn != 0)
> + return PCIBIOS_FUNC_NOT_SUPPORTED;
> +
> + /*
> + * 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);
This is a major issue and possibly even a security problem.
Unprivileged users can cause config accesses via lspci/setpci.
I don't have a good suggestion for addressing it, but if you can't
make this work reliably, you need at least a dev_err() in the probe
function and probably a taint of the kernel (see add_taint()).
> + return ret;
> +}
> +
> +static int smp8759_config_write(struct pci_bus *bus,
> + unsigned int devfn, int where, int size, u32 val)
> +{
> + int ret;
> + struct pci_config_window *cfg = bus->sysdata;
> + struct tango_pcie *pcie = dev_get_drvdata(cfg->parent);
> +
> + writel_relaxed(1, pcie->mux);
> + ret = pci_generic_config_write(bus, devfn, where, size, val);
> + writel_relaxed(0, pcie->mux);
> +
> + return ret;
> +}
> +
> +static struct pci_ecam_ops smp8759_ecam_ops = {
> + .bus_shift = 20,
> + .pci_ops = {
> + .map_bus = pci_ecam_map_bus,
> + .read = smp8759_config_read,
> + .write = smp8759_config_write,
> + }
> +};
