wifi: rtw89: pci: enable LTR based on pcie control register

Originally, driver always transmits LTR (Latency Tolerance Reporting) to
pcie host, but it may cause pcie link down on some platforms because
LTR is not supported. As a result, driver will check the control
register of LTR setting to decide whether to enable LTR feature.

This applies to Wi-Fi 6 chips only. For Wi-Fi 7 chips, although the
driver still issues LTR, the hardware has its own internal logic
to determine whether to actually transmit it to pcie host.

Signed-off-by: Dian-Syuan Yang <dian_syuan0116@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20260515014433.16168-5-pkshih@realtek.com

diff --git a/drivers/net/wireless/realtek/rtw89/pci.c b/drivers/net/wireless/realtek/rtw89/pci.c
index 64554eb35a72cff22b6405775ce50aeb0bee34c5..f7107dc05b71aec184cc36d9124d786c61303c1d 100644 (file)
--- a/drivers/net/wireless/realtek/rtw89/pci.c
+++ b/drivers/net/wireless/realtek/rtw89/pci.c
@@ -3039,6 +3039,17 @@ static int rtw89_pci_mode_op(struct rtw89_dev *rtwdev)
        return 0;
 }
 
+static bool rtw89_pci_dev_ltr_enabled(struct rtw89_dev *rtwdev)
+{
+       struct rtw89_pci *rtwpci = (struct rtw89_pci *)rtwdev->priv;
+       struct pci_dev *pdev = rtwpci->pdev;
+       u16 cap;
+
+       pcie_capability_read_word(pdev, PCI_EXP_DEVCTL2, &cap);
+
+       return !!(cap & PCI_EXP_DEVCTL2_LTR_EN);
+}
+
 static int rtw89_pci_ops_deinit(struct rtw89_dev *rtwdev)
 {
        const struct rtw89_pci_info *info = rtwdev->pci_info;
@@ -3143,7 +3154,7 @@ int rtw89_pci_ltr_set(struct rtw89_dev *rtwdev, bool en)
 {
        u32 val;
 
-       if (!en)
+       if (!en || !rtw89_pci_dev_ltr_enabled(rtwdev))
                return 0;
 
        val = rtw89_read32(rtwdev, R_AX_LTR_CTRL_0);
@@ -3179,6 +3190,9 @@ int rtw89_pci_ltr_set_v1(struct rtw89_dev *rtwdev, bool en)
        u32 dec_ctrl;
        u32 val32;
 
+       if (!rtw89_pci_dev_ltr_enabled(rtwdev))
+               return 0;
+
        val32 = rtw89_read32(rtwdev, R_AX_LTR_CTRL_0);
        if (rtw89_pci_ltr_is_err_reg_val(val32))
                return -EINVAL;