[PATCH v6 2/4] Bluetooth: btintel_pcie: fix PM flow for S0ix, S3 and S4

[Ravindra <ravindra@intel.com>]

Fix two issues in the PM suspend/resume path:

1. S3 was handled the same as S0ix, keeping the controller on the
   D3hot-style path. That caused resume instability because S3 can
   remove power from the controller, unlike s2idle/S0ix. Use
   pm_suspend_target_state to distinguish them: D3_HOT for S0ix and
   D3_COLD for S3/S4. Add .restore to force FLR-based firmware recovery
   after S4 and S3 (PM_SUSPEND_MEM), as power is lost. S0ix resumes via
   a normal D0 transition.

2. During hibernation, .freeze() puts the controller into the D3cold
   state without any loss of power, and the flow normally continues to
   .poweroff(). If hibernation instead fails, .thaw() is called to bring
   the controller back up, and the old code routed it through
   btintel_pcie_resume(), which forced FLR-based firmware recovery
   whenever data->pm_sx_event was PM_EVENT_FREEZE. That check was
   incorrect: since the controller's power was never actually removed on
   this failed-hibernation path, FLR-based recovery is unnecessary. Remove
   pm_sx_event and route .thaw through a normal D0 transition instead;
   FLR-based recovery is retained only in .restore, where genuine S4
   power loss requires it.

Tested with:
  S0ix: sudo sh -c 'echo "+40" > /sys/class/rtc/rtc0/wakealarm' && \
        echo freeze | sudo tee /sys/power/state
  S3:   sudo rtcwake -m mem  -s 60
  S4:   sudo rtcwake -m disk -s 60

Fixes: e57362f4911b ("Bluetooth: btintel_pcie: Add support for _suspend() / _resume()")
Assisted-by: GitHub-Copilot:GPT5
Signed-off-by: Ravindra <ravindra@intel.com>
Tested-by: Sergey Lebedev <lsa.uz@pm.me>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
---
 drivers/bluetooth/btintel_pcie.c | 58 +++++++++++++++++++++-----------
 drivers/bluetooth/btintel_pcie.h |  2 --
 2 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/drivers/bluetooth/btintel_pcie.c b/drivers/bluetooth/btintel_pcie.c
index 677749903173..082f5ec8ba71 100644
--- a/drivers/bluetooth/btintel_pcie.c
+++ b/drivers/bluetooth/btintel_pcie.c
@@ -16,6 +16,7 @@
 #include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/acpi.h>
+#include <linux/suspend.h>
 
 #include <linux/unaligned.h>
 #include <linux/devcoredump.h>
@@ -4199,7 +4200,8 @@ static void btintel_pcie_coredump(struct device *dev)
 
 static int btintel_pcie_set_dxstate(struct btintel_pcie_data *data, u32 dxstate)
 {
-	int retry = 0, status;
+	int retry = 0;
+	long status;
 	u32 dx_intr_timeout_ms = 200;
 
 	do {
@@ -4251,18 +4253,23 @@ static int btintel_pcie_suspend_late(struct device *dev, pm_message_t mesg)
 
 	data = pci_get_drvdata(pdev);
 
-	dxstate = (mesg.event == PM_EVENT_SUSPEND ?
-		   BTINTEL_PCIE_STATE_D3_HOT : BTINTEL_PCIE_STATE_D3_COLD);
-
-	data->pm_sx_event = mesg.event;
+	/* S0ix (s2idle) uses D3_HOT; S3, freeze and hibernate use D3_COLD. */
+	if (mesg.event == PM_EVENT_SUSPEND &&
+	    pm_suspend_target_state == PM_SUSPEND_TO_IDLE)
+		dxstate = BTINTEL_PCIE_STATE_D3_HOT;
+	else
+		dxstate = BTINTEL_PCIE_STATE_D3_COLD;
 
 	start = ktime_get();
 
 	/* Refer: 6.4.11.7 -> Platform power management */
 	err = btintel_pcie_set_dxstate(data, dxstate);
 
-	if (err)
+	if (err) {
+		bt_dev_err(data->hdev, "Failed to set dxstate:%u (%d)",
+			   dxstate, err);
 		return err;
+	}
 
 	bt_dev_dbg(data->hdev,
 		   "device entered into d3 state from d0 in %lld us",
@@ -4285,7 +4292,7 @@ static int btintel_pcie_freeze(struct device *dev)
 	return btintel_pcie_suspend_late(dev, PMSG_FREEZE);
 }
 
-static int btintel_pcie_resume(struct device *dev)
+static int btintel_pcie_resume_event(struct device *dev, pm_message_t mesg)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct btintel_pcie_data *data;
@@ -4293,19 +4300,15 @@ static int btintel_pcie_resume(struct device *dev)
 	int err;
 
 	data = pci_get_drvdata(pdev);
-	data->gp0_received = false;
 
 	start = ktime_get();
 
-	/* When the system enters S4 (hibernate) mode, bluetooth device loses
-	 * power, which results in the erasure of its loaded firmware.
-	 * Consequently, function level reset (flr) is required on system
-	 * resume to bring the controller back into an operational state by
-	 * initiating a new firmware download.
+	/* S3 and S4 may cut power, erasing the firmware. Force FLR to recover
+	 * instead of a normal D0 transition.
 	 */
-
-	if (data->pm_sx_event == PM_EVENT_FREEZE ||
-	    data->pm_sx_event == PM_EVENT_HIBERNATE) {
+	if (mesg.event == PM_EVENT_RESTORE ||
+	    (mesg.event == PM_EVENT_RESUME &&
+	     pm_suspend_target_state == PM_SUSPEND_MEM)) {
 		set_bit(BTINTEL_PCIE_CORE_HALTED, &data->flags);
 		btintel_pcie_request_reset(data, BTINTEL_PCIE_IOSF_PRR_FLR);
 		return 0;
@@ -4314,7 +4317,9 @@ static int btintel_pcie_resume(struct device *dev)
 	/* Refer: 6.4.11.7 -> Platform power management */
 	err = btintel_pcie_set_dxstate(data, BTINTEL_PCIE_STATE_D0);
 
-	if (err == 0) {
+	if (err) {
+		bt_dev_err(data->hdev, "Failed to set D0 state (%d)", err);
+	} else {
 		bt_dev_dbg(data->hdev,
 			   "device entered into d0 state from d3 in %lld us",
 			   ktime_to_us(ktime_get() - start));
@@ -4339,13 +4344,28 @@ static int btintel_pcie_resume(struct device *dev)
 	return err;
 }
 
+static int btintel_pcie_resume(struct device *dev)
+{
+	return btintel_pcie_resume_event(dev, PMSG_RESUME);
+}
+
+static int btintel_pcie_restore(struct device *dev)
+{
+	return btintel_pcie_resume_event(dev, PMSG_RESTORE);
+}
+
+static int btintel_pcie_thaw(struct device *dev)
+{
+	return btintel_pcie_resume_event(dev, PMSG_THAW);
+}
+
 static const struct dev_pm_ops btintel_pcie_pm_ops = {
 	.suspend = btintel_pcie_suspend,
 	.resume = btintel_pcie_resume,
 	.freeze = btintel_pcie_freeze,
-	.thaw = btintel_pcie_resume,
+	.thaw = btintel_pcie_thaw,
 	.poweroff = btintel_pcie_hibernate,
-	.restore = btintel_pcie_resume,
+	.restore = btintel_pcie_restore,
 };
 
 static struct pci_driver btintel_pcie_driver = {
diff --git a/drivers/bluetooth/btintel_pcie.h b/drivers/bluetooth/btintel_pcie.h
index 016795fcbccc..3030b4e8b750 100644
--- a/drivers/bluetooth/btintel_pcie.h
+++ b/drivers/bluetooth/btintel_pcie.h
@@ -713,7 +713,6 @@ struct btintel_pcie_ini_dump_info {
  * @txq: TX Queue struct
  * @rxq: RX Queue struct
  * @alive_intr_ctxt: Alive interrupt context
- * @pm_sx_event: PM event on which system got suspended
  */
 struct btintel_pcie_data {
 	struct pci_dev	*pdev;
@@ -773,7 +772,6 @@ struct btintel_pcie_data {
 	struct btintel_pcie_dbgc	dbgc;
 	struct btintel_pcie_mdbgc	mdbgc;
 	struct btintel_pcie_dump_header dmp_hdr;
-	u8	pm_sx_event;
 	u32	debug_evt_addr;
 	u32	debug_evt_size;
 	dma_addr_t	debug_table_addr;
-- 
2.43.0