Arnd Bergmann wrote: > > On Wednesday 23 April 2014 15:23:16 Liviu Dudau wrote: > > > Unfortunately we are in a tricky situation on arm64 because we have > > > to support both server-type SoCs and embedded-type SoCs. In an > > > embedded system, you can't trust the boot loader to do a proper > > > setup of all the hardware, so the kernel needs full control over > > > all the initialization. In a server, the initialization is the > > > responsibility of the firmware, and we don't want the kernel to > > > even know about those registers. BTW, actually we can trust boot-loader to do required things in mobile also ;-) > > > > > > My hope is that all server chips use an SBSA compliant PCIe > > > implementation, but we already have X-Gene, which is doing server > > > workloads with a nonstandard PCIe, and it's possible that there > > > will also be server-like systems with a DesignWare PCIe block > > > instead of an SBSA compliant one. We can still support those, but > > > I don't want to see more than one implementation of dw-pcie > > > on servers. Just like we have the generic PCIe support that Will > > > is doing for virtual machines and SBSA compliant systems, we > > > would do one dw-pcie variant for all systems that come with a > > > host firmware and rely on it being set up already. OK and I think, just one device driver would be nice for whatever embedded or server. > > > > There is nothing in the SBSA that mandates firmware setup. All it requires Yeah, I couldn't look at that in the SBSA... > > is that hardware is setup in a way that is not specific to a board > > or a particular OEM. Surely if the setup being done for GH7 is always > > the same it should fit the bill? > But Arnd's comments are about firmware based on each SoC not board?... > GH7 is already not SBSA compliant because it uses a nonstandard config > space access method, and it uses its own MSI controller rather than GIC. > This means it violates at least two out of the four clauses in SBSA > describing PCIe. > OK, I see. Honestly, we just focused on how to support PCI on both exynos5440 and GH7 SoCs. > Regardless of this, the level of detail describing config space and > MSI handling in SBSA can only make sense if the purpose is to handle > all compliant implementations without platform specific code. If you > require platform specific setup code in the OS, this underlying assumption > no longer holds true and there is no point in having a spec in the > first place. > OK, your assumption makes sense to us. > I think we should treat DW-PCIe in the same way if anyone attempts > to use that in a server, e.g. in SBSA level 0. As you can see here, Agreed. BTW, how about GICv2m for level 1? It can be supported with the same way in one DW-PCIe driver? > even when reusing hardware between Exynos and GH7, you can't just > use the same init code, so it has to be in firmware to be any good. > On a real server platform, you can't require a kernel upgrade every > time a new SoC comes out, any basic functionality like PCI just has to > work with existing OS images. > OK, when Will's driver is ready, we will test it on GH7 with the setup for PCIe included in firmware. Anyway I hope we can use the driver in 3.16 :-) Thanks, Kukjin -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
