From 9ea4dcf49878bb9546b8fa9319dcbdc9b7ee20f8 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 22 Apr 2022 15:58:11 -0700 Subject: PM: CXL: Disable suspend The CXL specification claims S3 support at a hardware level, but at a system software level there are some missing pieces. Section 9.4 (CXL 2.0) rightly claims that "CXL mem adapters may need aux power to retain memory context across S3", but there is no enumeration mechanism for the OS to determine if a given adapter has that support. Moreover the save state and resume image for the system may inadvertantly end up in a CXL device that needs to be restored before the save state is recoverable. I.e. a circular dependency that is not resolvable without a third party save-area. Arrange for the cxl_mem driver to fail S3 attempts. This still nominaly allows for suspend, but requires unbinding all CXL memory devices before the suspend to ensure the typical DRAM flow is taken. The cxl_mem unbind flow is intended to also tear down all CXL memory regions associated with a given cxl_memdev. It is reasonable to assume that any device participating in a System RAM range published in the EFI memory map is covered by aux power and save-area outside the device itself. So this restriction can be minimized in the future once pre-existing region enumeration support arrives, and perhaps a spec update to clarify if the EFI memory map is sufficent for determining the range of devices managed by platform-firmware for S3 support. Per Rafael, if the CXL configuration prevents suspend then it should fail early before tasks are frozen, and mem_sleep should stop showing 'mem' as an option [1]. Effectively CXL augments the platform suspend ->valid() op since, for example, the ACPI ops are not aware of the CXL / PCI dependencies. Given the split role of platform firmware vs OS provisioned CXL memory it is up to the cxl_mem driver to determine if the CXL configuration has elements that platform firmware may not be prepared to restore. Link: https://lore.kernel.org/r/CAJZ5v0hGVN_=3iU8OLpHY3Ak35T5+JcBM-qs8SbojKrpd0VXsA@mail.gmail.com [1] Cc: "Rafael J. Wysocki" Cc: Pavel Machek Cc: Len Brown Reviewed-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/165066828317.3907920.5690432272182042556.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams --- include/linux/pm.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux/pm.h') diff --git a/include/linux/pm.h b/include/linux/pm.h index e65b3ab28377..7911c4c9a7be 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -36,6 +36,15 @@ static inline void pm_vt_switch_unregister(struct device *dev) } #endif /* CONFIG_VT_CONSOLE_SLEEP */ +#ifdef CONFIG_CXL_SUSPEND +bool cxl_mem_active(void); +#else +static inline bool cxl_mem_active(void) +{ + return false; +} +#endif + /* * Device power management */ -- cgit v1.3-8-gc7d7 From 5b71808eb7c97815fc3b9c386ca0ef6daf2dc053 Mon Sep 17 00:00:00 2001 From: Dmitry Osipenko Date: Tue, 10 May 2022 02:32:32 +0300 Subject: reboot: Remove pm_power_off_prepare() All pm_power_off_prepare() users were converted to sys-off handler API. Remove the obsolete global callback variable. Signed-off-by: Dmitry Osipenko Signed-off-by: Rafael J. Wysocki --- include/linux/pm.h | 1 - kernel/reboot.c | 19 ------------------- 2 files changed, 20 deletions(-) (limited to 'include/linux/pm.h') diff --git a/include/linux/pm.h b/include/linux/pm.h index e65b3ab28377..3786d306dad2 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -21,7 +21,6 @@ * Callbacks for platform drivers to implement. */ extern void (*pm_power_off)(void); -extern void (*pm_power_off_prepare)(void); struct device; /* we have a circular dep with device.h */ #ifdef CONFIG_VT_CONSOLE_SLEEP diff --git a/kernel/reboot.c b/kernel/reboot.c index 673d3f54dcad..88c835167d9e 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -63,13 +63,6 @@ struct sys_off_handler { */ void __weak (*pm_power_off)(void); -/* - * If set, this is used for preparing the system to power off. - */ - -void (*pm_power_off_prepare)(void); -EXPORT_SYMBOL_GPL(pm_power_off_prepare); - /** * emergency_restart - reboot the system * @@ -524,14 +517,6 @@ void unregister_platform_power_off(void (*power_off)(void)) } EXPORT_SYMBOL_GPL(unregister_platform_power_off); -static int legacy_pm_power_off_prepare(struct sys_off_data *data) -{ - if (pm_power_off_prepare) - pm_power_off_prepare(); - - return NOTIFY_DONE; -} - static int legacy_pm_power_off(struct sys_off_data *data) { if (pm_power_off) @@ -549,10 +534,6 @@ static int legacy_pm_power_off(struct sys_off_data *data) */ static int __init legacy_pm_init(void) { - register_sys_off_handler(SYS_OFF_MODE_POWER_OFF_PREPARE, - SYS_OFF_PRIO_DEFAULT, - legacy_pm_power_off_prepare, NULL); - register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_DEFAULT, legacy_pm_power_off, NULL); -- cgit v1.3-8-gc7d7