Am Samstag, 23. August 2014, 09:35:05 schrieb Guenter Roeck: > 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. I don't think you can split the patches like this. Patch1 introduces (un)register_restart_handler functions used by later patches in the series. You therefore cannot really split the series, as otherwise you would get build failures in the individual trees. Heiko > - 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
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