On Tue, Aug 19, 2014 at 05:45:27PM -0700, Guenter Roeck wrote: > Various drivers implement architecture and/or device specific means > to restart (reset) the system. Various mechanisms have been implemented > to support those schemes. The best known mechanism is arm_pm_restart, > which is a function pointer to be set either from platform specific code > or from drivers. Another mechanism is to use hardware watchdogs to issue > a reset; this mechanism is used if there is no other method available > to reset a board or system. Two examples are alim7101_wdt, which currently > uses the reboot notifier to trigger a reset, and moxart_wdt, which registers > the arm_pm_restart function. Several other restart drivers for arm, all > directly calling arm_pm_restart, are in the process of being integrated > into the kernel. All those drivers would benefit from the new API. > > The existing mechanisms have a number of drawbacks. Typically only one scheme > to restart the system is supported (at least if arm_pm_restart is used). > At least in theory there can be multiple means to restart the system, some of > which may be less desirable (for example one mechanism may only reset the CPU, > while another may reset the entire system). Using arm_pm_restart can also be > racy if the function pointer is set from a driver, as the driver may be in > the process of being unloaded when arm_pm_restart is called. > Using the reboot notifier is always racy, as it is unknown if and when > other functions using the reboot notifier have completed execution > by the time the watchdog fires. > > Introduce a system restart handler call chain to solve the described problems. > This call chain is expected to be executed from the architecture specific > machine_restart() function. Drivers providing system restart functionality > (such as the watchdog drivers mentioned above) are expected to register > with this call chain. By using the priority field in the notifier block, > callers can control restart handler execution sequence and thus ensure that > the restart handler with the optimal restart capabilities for a given system > is called first. > > Since the first revision of this patchset, a number of separate patch > submissions have been made which either depend on it or could make use of it. > > http://www.spinics.net/linux/lists/arm-kernel/msg344796.html > registers three notifiers. > https://lkml.org/lkml/2014/7/8/962 > would benefit from it. > > Patch 1 of this series implements the restart handler function. Patches 2 and 3 > implement calling the restart handler chain from arm and arm64 restart code. > > Patch 4 modifies the restart-poweroff driver to no longer call arm_pm_restart > directly but machine_restart. This is done to avoid calling arm_pm_restart > from more than one place. The change makes the driver architecture independent, > so it would be possible to drop the arm dependency from its Kconfig entry. > > Patch 5 and 6 convert existing restart handlers in the watchdog subsystem > to use the restart handler. Patch 7 unexports arm_pm_restart to ensure > that no one gets the idea to implement a restart handler as module. > > The entire patch series, including additional patches depending on it, > is available from > https://git.kernel.org/cgit/linux/kernel/git/groeck/linux-staging.git/ > in branch 'restart-staging'. > Hi Andrew, I think this series is ready for upstream integration. Question now is how we should proceed to get it actually integrated. I can see a number of options: - You take patch #1, the rest goes in through maintainer trees. - You take all patches after we get missing maintainer Acks. - I send a pull request directly to Linus after we get missing maintainer Acks. What do you think would be the best way to proceed ? Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
 |