On 24 August 2017 at 21:02, Rob Herring <robh@xxxxxxxxxx> wrote: > Cc the DT list for bindings please. > > On Thu, Aug 24, 2017 at 1:43 PM, Ard Biesheuvel > <ard.biesheuvel@xxxxxxxxxx> wrote: >> Describe the binding for firmware-configured instances of the Synopsys >> Designware PCIe controller in RC mode. >> >> Cc: Rob Herring <robh@xxxxxxxxxx> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> >> --- >> Documentation/devicetree/bindings/pci/designware-pcie-ecam.txt | 56 ++++++++++++++++++++ >> 1 file changed, 56 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/pci/designware-pcie-ecam.txt b/Documentation/devicetree/bindings/pci/designware-pcie-ecam.txt >> new file mode 100644 >> index 000000000000..b8127b19c220 >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/pci/designware-pcie-ecam.txt >> @@ -0,0 +1,56 @@ >> +* Synopsys Designware PCIe root complex in ECAM mode >> + >> +In some cases, firmware may already have configured the Synopsys Designware >> +PCIe controller in RC mode with static ATU window mappings that cover all >> +config, MMIO and I/O spaces in a [mostly] ECAM compatible fashion. >> +In this case, there is no need for the OS to perform any low level setup >> +of clocks or device registers, nor is there any reason for the driver to >> +reconfigure ATU windows for config and/or IO space accesses at runtime. >> + >> +Such hardware configurations should be described as "pci-host-ecam-generic" >> +if they are truly ECAM compatible. Configurations that require no low-level >> +setup by the OS nor any ATU window reconfiguration at runtime, but do >> +require special handling for type 0 config TLPs may instead be described as >> +"snps,dw-pcie-ecam". > > Humm, what happens when we have the next exception that's SoC specific > or another vendor? This is not SoC specific, but IP specific. We are working with two different SoCs from completely different vendors that both synthesized this IP with a 64 KB ATU window size, not expecting this to break ECAM compatibility. > Seems like perhaps "firmware initialized" should > have been a separate property flag for bootloaders to add rather than > a compatible string. > Yes, but then you still have 10 different drivers that all retain the low-level bits that are all different between SoCs. That is exactly what I want to get rid of, and usually we can do that with existing bindings, because we simply expose it as pci-host-ecam-generic. Only in this particular case, that doesn't fly due to the quirk. > I'd rather see this done in a way that does not require DT updates if > quirks have to be handled/added later. > Do you see a way that still allows us to keep the abstraction? I don't want a flag, I simply don't want to expose any low-level specifics about the device to the OS, beyond what it needs to use it in its configured state.
