wifi: ath11k: restore register window after global reset

Hardware target implements an address space larger than that PCI BAR can
map. In order to be able to access the whole target address space, the BAR
space is split into 4 segments, of which the last 3, called windows, can
be dynamically mapped to the desired area. This is achieved by updating
window register with appropriate window value. Currently each time when
accessing a register that beyond ATH11K_PCI_WINDOW_START, host calculates
the window value and caches it after window update, this way next time
when accessing a register falling in the same window, host knows that the
window is already good hence no additional update needed.

However this mechanism breaks after global reset is triggered in
ath11k_pci_soc_global_reset(), because with global reset hardware resets
window register hence the window is not properly mapped any more. Current
host does nothing about this, as a result a subsequent register access may
not work as expected if it falls in a window same as before.

Although there is no obvious issue seen now, better to fix it to avoid
future problem. The fix is done by restoring the window register after
global reset.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30

Fixes: d5c65159f289 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Signed-off-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/20251014-ath11k-reset-window-cache-v1-1-b85271b111dd@oss.qualcomm.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/drivers/net/wireless/ath/ath11k/pci.c b/drivers/net/wireless/ath/ath11k/pci.c
index d8655badd96d..7114eca8810d 100644
--- a/drivers/net/wireless/ath/ath11k/pci.c
+++ b/drivers/net/wireless/ath/ath11k/pci.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: BSD-3-Clause-Clear
 /*
  * Copyright (c) 2019-2020 The Linux Foundation. All rights reserved.
- * Copyright (c) 2021-2025 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
  */
 
 #include <linux/module.h>
@@ -177,6 +177,19 @@ static inline void ath11k_pci_select_static_window(struct ath11k_pci *ab_pci)
 		  ab_pci->ab->mem + ATH11K_PCI_WINDOW_REG_ADDRESS);
 }
 
+static void ath11k_pci_restore_window(struct ath11k_base *ab)
+{
+	struct ath11k_pci *ab_pci = ath11k_pci_priv(ab);
+
+	spin_lock_bh(&ab_pci->window_lock);
+
+	iowrite32(ATH11K_PCI_WINDOW_ENABLE_BIT | ab_pci->register_window,
+		  ab->mem + ATH11K_PCI_WINDOW_REG_ADDRESS);
+	ioread32(ab->mem + ATH11K_PCI_WINDOW_REG_ADDRESS);
+
+	spin_unlock_bh(&ab_pci->window_lock);
+}
+
 static void ath11k_pci_soc_global_reset(struct ath11k_base *ab)
 {
 	u32 val, delay;
@@ -201,6 +214,11 @@ static void ath11k_pci_soc_global_reset(struct ath11k_base *ab)
 	val = ath11k_pcic_read32(ab, PCIE_SOC_GLOBAL_RESET);
 	if (val == 0xffffffff)
 		ath11k_warn(ab, "link down error during global reset\n");
+
+	/* Restore window register as its content is cleared during
+	 * hardware global reset, such that it aligns with host cache.
+	 */
+	ath11k_pci_restore_window(ab);
 }
 
 static void ath11k_pci_clear_dbg_registers(struct ath11k_base *ab)