platform/x86: ideapad-laptop: use usleep_range() for EC polling
commit 5808c342 upstream. It was reported that ideapad-laptop sometimes causes some recent (since 2024) Lenovo ThinkBook models shut down when: - suspending/resuming - closing/opening the lid - (dis)connecting a charger - reading/writing some sysfs properties, e.g., fan_mode, touchpad - pressing down some Fn keys, e.g., Brightness Up/Down (Fn+F5/F6) - (seldom) loading the kmod The issue has existed since the launch day of such models, and there have been some out-of-tree workarounds (see Link:) for the issue. One disables some functionalities, while another one simply shortens IDEAPAD_EC_TIMEOUT. The disabled functionalities have read_ec_data() in their call chains, which calls schedule() between each poll. It turns out that these models suffer from the indeterminacy of schedule() because of their low tolerance for being polled too frequently. Sometimes schedule() returns too soon due to the lack of ready tasks, causing the margin between two polls to be too short. In this case, the command is somehow aborted, and too many subsequent polls (they poll for "nothing!") may eventually break the state machine in the EC, resulting in a hard shutdown. This explains why shortening IDEAPAD_EC_TIMEOUT works around the issue - it reduces the total number of polls sent to the EC. Even when it doesn't lead to a shutdown, frequent polls may also disturb the ongoing operation and notably delay (+ 10-20ms) the availability of EC response. This phenomenon is unlikely to be exclusive to the models mentioned above, so dropping the schedule() manner should also slightly improve the responsiveness of various models. Fix these issues by migrating to usleep_range(150, 300). The interval is chosen to add some margin to the minimal 50us and considering EC responses are usually available after 150-2500us based on my test. It should be enough to fix these issues on all models subject to the EC bug without introducing latency on other models. Tested on ThinkBook 14 G7+ ASP and solved both issues. No regression was introduced in the test on a model without the EC bug (ThinkBook X IMH, thanks Eric). Link: https://github.com/ty2/ideapad-laptop-tb2024g6plus/commit/6c5db18c9e8109873c2c90a7d2d7f552148f7ad4 Link: https://github.com/ferstar/ideapad-laptop-tb/commit/42d1e68e5009529d31bd23f978f636f79c023e80 Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218771 Fixes: 6a09f21d ("ideapad: add ACPI helpers") Cc: stable@vger.kernel.org Tested-by:Felix Yan <felixonmars@archlinux.org> Tested-by:
Eric Long <i@hack3r.moe> Tested-by:
Jianfei Zhang <zhangjianfei3@gmail.com> Tested-by:
Mingcong Bai <jeffbai@aosc.io> Tested-by:
Minh Le <minhld139@gmail.com> Tested-by:
Sicheng Zhu <Emmet_Z@outlook.com> Signed-off-by:
Rong Zhang <i@rong.moe> Link: https://lore.kernel.org/r/20250525201833.37939-1-i@rong.moe Reviewed-by:
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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