[PATCH 1/2] wifi: ath12k: skip PCIe global reset on initial power-up

[Nazar Mokrynskyi]

ath12k_pci_sw_reset() unconditionally calls ath12k_pci_soc_global_reset()
regardless of whether the device is being powered up for the first time or
recovering from a previous run. The global reset drops the PCIe link and
relies on the host root complex to perform physical link retraining before
the MHI BHI register can be accessed.

When the device is passed through to a VM via VFIO, no physical link
retraining occurs after the reset since QEMU's virtual PCIe bridge does
not implement hardware LTSSM negotiation. As a result, all subsequent
MMIO reads return 0xffffffff and MHI initialization fails with -EREMOTEIO.

On initial power-up, vfio-pci has already performed a Function Level
Reset before handing the device to the guest driver, placing it in a
known clean state equivalent to what the global reset achieves. The global
reset is therefore redundant on power-up and only necessary on the
shutdown/recovery path where it tears down an already-running firmware.

Skip ath12k_pci_soc_global_reset() when power_on is true to allow MHI
initialization to succeed under VFIO passthrough without affecting bare
metal behavior.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.6-01243-QCAHKSWPL_SILICONZ-1

Signed-off-by: Nazar Mokrynskyi <nazar at mokrynskyi.com>
---
 drivers/net/wireless/ath/ath12k/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath12k/pci.c b/drivers/net/wireless/ath/ath12k/pci.c
index 375277ca2..a3d7aeb72 100644
--- a/drivers/net/wireless/ath/ath12k/pci.c
+++ b/drivers/net/wireless/ath/ath12k/pci.c
@@ -303,7 +303,8 @@ static void ath12k_pci_sw_reset(struct ath12k_base *ab, bool power_on)
 
 	ath12k_mhi_clear_vector(ab);
 	ath12k_pci_clear_dbg_registers(ab);
-	ath12k_pci_soc_global_reset(ab);
+	if (!power_on)
+		ath12k_pci_soc_global_reset(ab);
 	ath12k_mhi_set_mhictrl_reset(ab);
 }
 
-- 
2.43.0