platform/x86: intel/pmc: Ignore all LTRs during suspend

Add support to ignore all LTRs before suspend and restore the previous
LTR values after suspend. This feature could be turned off with module
parameter ltr_ignore_all_suspend.

LTR value is a mechanism for a device to indicate tolerance to access
the corresponding resource. When system suspends, the resource is not
available and therefore the LTR value could be ignored. Ignoring all
LTR values prevents problematic device from blocking the system to get
to the deepest package state during suspend.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Xi Pardee <xi.pardee@intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240906184016.268153-1-xi.pardee@linux.intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Author: xpardee-create

drivers/platform/x86/intel/pmc/core.c

@@ -714,6 +714,49 @@ static int pmc_core_s0ix_blocker_show(struct seq_file *s, void *unused)
 }
 DEFINE_SHOW_ATTRIBUTE(pmc_core_s0ix_blocker);
 
+static void pmc_core_ltr_ignore_all(struct pmc_dev *pmcdev)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(pmcdev->pmcs); i++) {
+		struct pmc *pmc;
+		u32 ltr_ign;
+
+		pmc = pmcdev->pmcs[i];
+		if (!pmc)
+			continue;
+
+		guard(mutex)(&pmcdev->lock);
+		pmc->ltr_ign = pmc_core_reg_read(pmc, pmc->map->ltr_ignore_offset);
+
+		/* ltr_ignore_max is the max index value for LTR ignore register */
+		ltr_ign = pmc->ltr_ign | GENMASK(pmc->map->ltr_ignore_max, 0);
+		pmc_core_reg_write(pmc, pmc->map->ltr_ignore_offset, ltr_ign);
+	}
+
+	/*
+	 * Ignoring ME during suspend is blocking platforms with ADL PCH to get to
+	 * deeper S0ix substate.
+	 */
+	pmc_core_send_ltr_ignore(pmcdev, 6, 0);
+}
+
+static void pmc_core_ltr_restore_all(struct pmc_dev *pmcdev)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(pmcdev->pmcs); i++) {
+		struct pmc *pmc;
+
+		pmc = pmcdev->pmcs[i];
+		if (!pmc)
+			continue;
+
+		guard(mutex)(&pmcdev->lock);
+		pmc_core_reg_write(pmc, pmc->map->ltr_ignore_offset, pmc->ltr_ign);
+	}
+}
+
 static inline u64 adjust_lpm_residency(struct pmc *pmc, u32 offset,
 				       const int lpm_adj_x2)
 {
@@ -1485,6 +1528,10 @@ static bool warn_on_s0ix_failures;
 module_param(warn_on_s0ix_failures, bool, 0644);
 MODULE_PARM_DESC(warn_on_s0ix_failures, "Check and warn for S0ix failures");
 
+static bool ltr_ignore_all_suspend = true;
+module_param(ltr_ignore_all_suspend, bool, 0644);
+MODULE_PARM_DESC(ltr_ignore_all_suspend, "Ignore all LTRs during suspend");
+
 static __maybe_unused int pmc_core_suspend(struct device *dev)
 {
 	struct pmc_dev *pmcdev = dev_get_drvdata(dev);
@@ -1494,6 +1541,9 @@ static __maybe_unused int pmc_core_suspend(struct device *dev)
 	if (pmcdev->suspend)
 		pmcdev->suspend(pmcdev);
 
+	if (ltr_ignore_all_suspend)
+		pmc_core_ltr_ignore_all(pmcdev);
+
 	/* Check if the syspend will actually use S0ix */
 	if (pm_suspend_via_firmware())
 		return 0;
@@ -1600,6 +1650,9 @@ static __maybe_unused int pmc_core_resume(struct device *dev)
 {
 	struct pmc_dev *pmcdev = dev_get_drvdata(dev);
 
+	if (ltr_ignore_all_suspend)
+		pmc_core_ltr_restore_all(pmcdev);
+
 	if (pmcdev->resume)
 		return pmcdev->resume(pmcdev);
 

drivers/platform/x86/intel/pmc/core.h

@@ -372,6 +372,7 @@ struct pmc_info {
  * @map:		pointer to pmc_reg_map struct that contains platform
  *			specific attributes
  * @lpm_req_regs:	List of substate requirements
+ * @ltr_ign:		Holds LTR ignore data while suspended
  *
  * pmc contains info about one power management controller device.
  */
@@ -380,6 +381,7 @@ struct pmc {
 	void __iomem *regbase;
 	const struct pmc_reg_map *map;
 	u32 *lpm_req_regs;
+	u32 ltr_ign;
 };
 
 /**