On Tuesday 06 January 2015 14:11:33 Catalin Marinas wrote: > On Tue, Jan 06, 2015 at 01:59:27PM +0000, Arnd Bergmann wrote: > > On Tuesday 06 January 2015 11:20:01 Catalin Marinas wrote: > > > On Mon, Jan 05, 2015 at 08:16:30PM +0000, Arnd Bergmann wrote: > > > > On Monday 05 January 2015 13:13:02 Catalin Marinas wrote: > > > > > > since passing no DT tables to OS but > > > > > > acpi=force is missing is a corner case, we can do a follow up patch to > > > > > > fix that, does it make sense? > > > > > > > > > > Not entirely. Why would no dtb and no acpi=force be a corner case? I > > > > > thought this should be the default when only ACPI tables are passed, no > > > > > need for an additional acpi=force argument. > > > > > > > > We don't really support the case of only ACPI tables for now. The expectation > > > > is that you always have working DT support, at least for the next few years > > > > as ACPI features are ramping up, and without acpi=force it should not try > > > > to use ACPI at all. > > > > > > So if both DT and ACPI are present, just use DT unless acpi=force is > > > passed. So far I think we agree but what I want to avoid is always > > > mandating acpi=force even when the DT tables are missing (in the long > > > run). > > > > > > Now, what's preventing a vendor firmware from providing only ACPI > > > tables? Do we enforce it in some way (arm-acpi.txt, kernel warning etc.) > > > that both DT and ACPI are supported, or at least that dts files are > > > merged in the kernel first? > > > > We have no way of enforcing what a board vendor ships, so if they want > > to have ACPI-only machines for MS Windows, they just won't work by > > default on Linux. > > What do you mean by "won't work by default on Linux"? Assuming no > additional drivers are needed (i.e. a few devices mentioned in SBSA and > the rest on a PCIe bus, using existing drivers without further > modifications), do you still want mainline to fail to boot on such > ACPI-only systems? I mean it won't work without acpi=force on the command line. > > Once ACPI support is mature enough, we can also have a whitelist or a > > different default for using it automatically when no DT is present. > > Having a white-list requires some for of SoC identification. Does ACPI > provide such thing (like "model" or "compatible" strings in the top DT > node)? This is independent of the SoC: All SoCs we support have DT drivers, so machines like this would be board whose vendor doesn't care about Linux, but happens to use a SoC that we support. What we would need here is a whitelist of boards. > > For drivers merged upstream, I would insist that every driver merged > > for an ARM64 platform has a documented DT binding that is used in the > > driver. > > That's fine by me. I just hope that for hardware aimed at ACPI we won't > need many non-PCIe drivers. Yes, that is a reasonable assumption. Looking at the AMD patches that were posted already, there are however a few devices that are not on the PCI bus: - pl011 uart - pl022 spi - pl061 gpio - pl330 dma - designware i2c - custom 10gbit ethernet - probably some I forgot Most of these will likely just not be needed on servers (pl330) or handled by AML (spi, i2c, gpio) transparently without needing a driver, but we do need to support the ethernet port and the uart. I expect that other SoCs come with different ethernet implementations that are also not discoverable through PCI. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
