On Mon 10 Jun 02:22 PDT 2019, Lee Jones wrote: > On Mon, 10 Jun 2019, Ard Biesheuvel wrote: > > > On Mon, 10 Jun 2019 at 10:55, Lee Jones <lee.jones@xxxxxxxxxx> wrote: > > > > > > On Mon, 10 Jun 2019, Ard Biesheuvel wrote: > > > > > > > On Mon, 10 Jun 2019 at 10:42, Lee Jones <lee.jones@xxxxxxxxxx> wrote: > > > > > > > > > > This patch provides basic support for booting with ACPI instead > > > > > of the currently supported Device Tree. When doing so there are a > > > > > couple of differences which we need to taken into consideration. > > > > > > > > > > Firstly, the SDM850 ACPI tables omit information pertaining to the > > > > > 4 reserved GPIOs on the platform. If Linux attempts to touch/ > > > > > initialise any of these lines, the firmware will restart the > > > > > platform. > > > > > > > > > > Secondly, when booting with ACPI, it is expected that the firmware > > > > > will set-up things like; Regulators, Clocks, Pin Functions, etc in > > > > > their ideal configuration. Thus, the possible Pin Functions > > > > > available to this platform are not advertised when providing the > > > > > higher GPIOD/Pinctrl APIs with pin information. > > > > > > > > > > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> > > > > > > > > For the ACPI probing boilerplate: > > > > Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > > > > > > > > *However*, I really don't like hardcoding reserved GPIOs like this. > > > > What guarantee do we have that each and every ACPI system > > > > incorporating the QCOM0217 device has the exact same list of reserved > > > > GPIOs? > > > > > > This is SDM845 specific, so the chances are reduced. > > > > You don't know that. > > All the evidence I have to hand tells me that this is the case. Even > on very closely related variants Qualcomm uses different H/W blocks > for GPIO. > I presume with this you mean that e.g. the 835 laptops doesn't sport a QCOM0217? > > > However, if another SDM845 variant does crop up, also lacking the > > > "gpios" property, we will have to find another differentiating factor > > > between them and conduct some matching. What else can you do with > > > platforms supporting non-complete/non-forthcoming ACPI tables? > > > > > > > Either we don't touch any pins at all if they are not referenced > > explicitly anywhere > > I guess this would require an API change, which is out of scope of > this patch-set. Happy to change this implementation later if the > subsystem allows for it though. > Last time we discussed this the _only_ offender was the loop issuing a get_direction() on all descs towards the end of gpiochip_add_data_with_key() > > or we parse the PEP tables, which seem to cover > > some of this information (if Bjorn's analysis is correct) > > Maybe someone can conduct some further work on this when we start to > enable or write a driver for the PEP (Windows-compatible System Power > Management Controller). The tables for the PEP look pretty complex, > so this task would be extremely difficult if not impossible without > Qualcomm's help. I wouldn't even know how to extrapolate this > information from the tables. > Yeah that looks quite different, so I'm not sure how to tie that into the current driver. But I'm fine with adding this for now, if PEP brings a different approach we can always rip this out later. Regards, Bjorn > > (if Bjorn's analysis is correct) > > Bjorn is about to provide his Reviewed-by for this implementation. > > -- > Lee Jones [?????????] > Linaro Services Technical Lead > Linaro.org ??? Open source software for ARM SoCs > Follow Linaro: Facebook | Twitter | Blog
