On Wed, Apr 17, 2024 at 03:01:00PM -0700, Florian Fainelli wrote: > On 4/17/24 14:54, Elliot Berman wrote: > > On Tue, Apr 16, 2024 at 10:35:22AM +0100, Sudeep Holla wrote: > > > On Sun, Apr 14, 2024 at 12:30:23PM -0700, Elliot Berman wrote: > > > > The PSCI SYSTEM_RESET2 call allows vendor firmware to define additional > > > > reset types which could be mapped to the reboot argument. > > > > > > > > Setting up reboot on Qualcomm devices can be inconsistent from chipset > > > > to chipset. > > > > > > That doesn't sound good. Do you mean PSCI SYSTEM_RESET doesn't work as > > > expected ? Does it mean it is not conformant to the specification ? > > > > > > > I was motivating the reason for using SYSTEM_RESET2. How to set the PMIC > > register and IMEM cookie can change between chipsets. Using > > SYSTEM_RESET2 alows us to abstract how to perform the reset. > > > > > > Generally, there is a PMIC register that gets written to > > > > decide the reboot type. There is also sometimes a cookie that can be > > > > written to indicate that the bootloader should behave differently than a > > > > regular boot. These knobs evolve over product generations and require > > > > more drivers. Qualcomm firmwares are beginning to expose vendor > > > > SYSTEM_RESET2 types to simplify driver requirements from Linux. > > > > > > > > > > Why can't this be fully userspace driven ? What is the need to keep the > > > cookie in the DT ? > > > > As Dmitry pointed out, this information isn't discoverable. I suppose > > we could technically use bootconfig or kernel command-line to convey the > > map although I think devicetree is the right spot for this mapping. > > > > - Other vendor-specific bits for PSCI are described in the devicetree. > > One example is the suspend param (e.g. the StateID) for cpu idle > > states. > > - Describing firmware bits in the DT isn't unprecedented, and putting > > this information outside the DT means that other OSes (besides Linux) > > need their own way to convey this information. > > - PSCI would be the odd one out that reboot mode map is not described in > > DT. Other reboot-mode drivers specify the mapping in the DT. Userspace > > that runs with firmware that support vendor reset2 need to make sure > > they can configure the mapping early enough. > > FWIW, I read Sudeep's response as being specifically inquiring about the > 'cookie' parameter, do you see a need for that to be in described in the DT > or could that just be an user-space parameter that is conveyed through the > reboot system call? Ah, I had thought the ask was for the reboot type as well as the cookie. We don't do this for hardware-based reboot mode cookies and I didn't see why we should ask userspace to do something different for PSCI. It seems to me that SYSTEM_RESET2 fits nicely with the existing design for reboot-mode bindings.
