rtw88: pci: disable aspm for platform inter-op with module parameter

Some platforms cannot read the DBI register successfully for the
ASPM settings. After the read failed, the bus could be unstable,
and the device just became unavailable [1]. For those platforms,
the ASPM should be disabled. But as the ASPM can help the driver
to save the power consumption in power save mode, the ASPM is still
needed. So, add a module parameter for them to disable it, then
the device can still work, while others can benefit from the less
power consumption that brings by ASPM enabled.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=206411
[2] Note that my lenovo T430 is the same.

Fixes: 3dff7c6e ("rtw88: allows to enable/disable HCI link PS mechanism")
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200605074703.32726-1-yhchuang@realtek.com

drivers/net/wireless/realtek/rtw88/pci.c

@@ -14,8 +14,11 @@
 #include "debug.h"
 
 static bool rtw_disable_msi;
+static bool rtw_pci_disable_aspm;
 module_param_named(disable_msi, rtw_disable_msi, bool, 0644);
+module_param_named(disable_aspm, rtw_pci_disable_aspm, bool, 0644);
 MODULE_PARM_DESC(disable_msi, "Set Y to disable MSI interrupt support");
+MODULE_PARM_DESC(disable_aspm, "Set Y to disable PCI ASPM support");
 
 static u32 rtw_pci_tx_queue_idx_addr[] = {
 	[RTW_TX_QUEUE_BK]	= RTK_PCI_TXBD_IDX_BKQ,
@@ -1200,6 +1203,9 @@ static void rtw_pci_clkreq_set(struct rtw_dev *rtwdev, bool enable)
 	u8 value;
 	int ret;
 
+	if (rtw_pci_disable_aspm)
+		return;
+
 	ret = rtw_dbi_read8(rtwdev, RTK_PCIE_LINK_CFG, &value);
 	if (ret) {
 		rtw_err(rtwdev, "failed to read CLKREQ_L1, ret=%d", ret);
@@ -1219,6 +1225,9 @@ static void rtw_pci_aspm_set(struct rtw_dev *rtwdev, bool enable)
 	u8 value;
 	int ret;
 
+	if (rtw_pci_disable_aspm)
+		return;
+
 	ret = rtw_dbi_read8(rtwdev, RTK_PCIE_LINK_CFG, &value);
 	if (ret) {
 		rtw_err(rtwdev, "failed to read ASPM, ret=%d", ret);