On Tue, Mar 02, 2021 at 10:02:49PM -0700, Jeffrey Hugo wrote: > Sorry, just joining the thread now. Hopefully I'm addressing everything > targeted at me. > > I used to do kernel work on MSMs, then kernel work on server CPUs, but now I > do kernel work on AI accelerators. Never was on the firmware team, but I > have a lot of contacts in those areas. On my own time, I support Linux on > the Qualcomm laptops. > > Its not MS that needs to fix things (although there is plenty of things I > could point to that MS could fix), its the Qualcomm Windows FW folks. They > have told me a while ago they were planning on fixing this issue on some > future chipset, but apparently that hasn't happened yet. Sadly, once these > laptops ship, they are in a frozen maintenance mode. > > In my opinion, MS has allowed Qualcomm to get away with doing bad things in > ACPI on the Qualcomm laptops. The ACPI is not a true hardware description > that is OS agnostic as it should be, and probably violates the spec in many > ways. Instead, the ACPI is written against the Windows drivers, and has a > lot of OS driver crap pushed into it. > > The GPIO description is one such thing. > > As I understand it, any particular SoC will have a number of GPIOs supported > by the TLMM. 0 - N. Linux understands this. However, in the ACPI of the > Qualcomm Windows laptops, you will likely find atleast one GPIO number which > exceeds this N. These are "virtual" GPIOs, and are a construct of the > Windows Qualcomm TLMM driver and how it interfaces with the frameworks > within Windows. > > Some GPIO lines can be configured as wakeup sources by routing them to a > specific hardware block in the SoC (which block it is varies from SoC to > SoC). Windows has a specific weird way of handling this which requires a > unique "GPIO chip" to handle. GPIO chips in Windows contain 32 GPIOs, so > for each wakeup GPIO, the TLMM driver creates a GPIO chip (essentially > creating 32 GPIOs), and assigns the added GPIOs numbers which exceed N. The > TLMM driver has an internal mapping of which virtual GPIO number corresponds > to which real GPIO. > > So, ACPI says that some peripheral has GPIO N+X, which is not a real GPIO. > That peripheral goes and requests that GPIO, which gets routed to the TLMM > driver, and the TLMM driver translates that number to the real GPIO, and > provides the reference back to the peripheral, while also setting up the > special wakeup hardware. > > So, N+1 is the first supported wakup GPIO, N+1+32 is the next one, then > N+1+32+32, and so on. Jeffrey, Thanks so much for these great information! May I ask a bit more about how the virtual number N+1+32*n maps back to the real number (R)? For example of touchpad GPIO on Flex 5G, I think we have: N+1+32*n = 0x0280 N = 191 R = 24 If my math not bad, n = 14. How does 14 map to 24? Shawn
