[PATCH rtw-next 04/13] wifi: rtw89: pci: enable LTR based on pcie control register

[Ping-Ke Shih <pkshih@realtek.com>]

From: Dian-Syuan Yang <dian_syuan0116@realtek.com>

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>
---
 drivers/net/wireless/realtek/rtw89/pci.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/realtek/rtw89/pci.c b/drivers/net/wireless/realtek/rtw89/pci.c
index 64554eb35a72..f7107dc05b71 100644
--- 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;
-- 
2.25.1