On Mon, Jun 17, 2024 at 10:18:09AM -0700, Elliot Berman wrote: > SoC vendors have different types of resets and are controlled through > various registers. For instance, Qualcomm chipsets can reboot to a > "download mode" that allows a RAM dump to be collected. Another example > is they also support writing a cookie that can be read by bootloader > during next boot. PSCI offers a mechanism, SYSTEM_RESET2, for these > vendor reset types to be implemented without requiring drivers for every > register/cookie. > > Add support in PSCI to statically map reboot mode commands from > userspace to a vendor reset and cookie value using the device tree. > > A separate initcall is needed to parse the devicetree, instead of using > psci_dt_init because mm isn't sufficiently set up to allocate memory. > > Reboot mode framework is close but doesn't quite fit with the > design and requirements for PSCI SYSTEM_RESET2. Some of these issues can > be solved but doesn't seem reasonable in sum: > 1. reboot mode registers against the reboot_notifier_list, which is too > early to call SYSTEM_RESET2. PSCI would need to remember the reset > type from the reboot-mode framework callback and use it > psci_sys_reset. > 2. reboot mode assumes only one cookie/parameter is described in the > device tree. SYSTEM_RESET2 uses 2: one for the type and one for > cookie. > 3. psci cpuidle driver already registers a driver against the > arm,psci-1.0 compatible. Refactoring would be needed to have both a > cpuidle and reboot-mode driver. > I need to think through it but when you first introduced the generic Documentation/devicetree/bindings/power/reset/reboot-mode.yaml bindings I also looked at drivers/power/reset/reboot-mode.c I assumed this extension to that binding would reuse the same and PSCI would just do reboot_mode_register(). I didn't expect to see these changes. I might have missing something but since the bindings is still quite generic with additional cells that act as additional cookie for reboot call, I still think that should be possible. What am I missing here then ? -- Regards, Sudeep
