On Tue, Feb 15, 2022 at 11:21:03AM +0000, Ben Dooks wrote: > On 14/02/2022 16:05, Bjorn Helgaas wrote: > > [+cc Rob for possible DT/kernel match issue, > > Lorenzo (native host bridge driver maintainer)] > > > > s/fix finding/Fix finding/ (in subject) > > Or even better, say something specific about the DT properties in > > question, e.g., look for "reset" instead of "reset-gpios". > > > > On Mon, Feb 14, 2022 at 08:21:43AM +0000, Ben Dooks wrote: > > > The calls to devm_gpiod_get_optional() have the -gpios at the end of > > > the name. This means the pcie driver is not finding the necessary > > > reset or power GPOOs to allow the PCIe devices on the SiFive Unmatched > > > boards. > > > > "to allow the PCIe devices ...?" Something is missing from this > > sentence. "To allow the devices <to do what>"? Or maybe the driver > > needs these GPIOs to power up the PCIe devices? > > > > I guess the implication is that the code looks for "reset-gpios" and > > "pwren-gpios", but the DT contains "reset" and "pwren"? > > > > But both Documentation/devicetree/bindings/pci/sifive,fu740-pcie.yaml > > and arch/riscv/boot/dts/sifive/fu740-c000.dtsi actually do contain > > "reset-gpios" and "pwren-gpios". > > Yes, the issue is the gpio core code adds either "-gpio" or "-gpios" > itself, thus the find code does not need this. The error messages and > DT are correct. I'll reword the initial paragraph to note that which > should also deal with the other comments: > > The calls to devm_gpiod_get_optional() have the -gpios at the end of > the name but the GPIO core code is already adding the suffix during > the lookup. This means the PCIe driver is not finding the necessary > reset or power lines to allow initialisation of the PCIe. Ah, that makes things make a LOT more sense! Please add something about "the '-gpios' suffix" for non-experts like me who don't know the inner workings of the GPIO core. The GPIO core seems slightly too helpful here -- we have to know about that detail to write error messages that make sense. > > If we *do* want to change the code, please change the error messages > > to match. > > See above, it is just devm_gpiod_get_optional() parameters at fault. > > > > This has not been a noted bug as the PCIe probe from u-boot has been > > > required to get the PCIe working due to other issues with the system > > > setup. It could have been broken since the driver inclusion, and not > > > been noticed as it is not necessary for the driver to funciton. > > > > Please add a line about what the connection between U-Boot and this > > issue is, e.g., maybe U-Boot powers up the devices, so we wouldn't > > notice the kernel's inability to do so? > > Does a reword to the following make better sense: > > This bug has not been noticed as if U-Boot has setup the GPIO lines > for the hardware when it does the PCIe initialisation (either by > booting from PCIe or user command to access PCIe) then the PCIe > will work in Linux. The U-Boot as supplied by SiFive does not by > default initialise any PCIe component. Sounds good, thanks. Bjorn
