ath9k: add MSI support

On new Intel platforms like ApolloLake, legacy interrupt mechanism
(INTx) is not supported, so WLAN modules are not working because
interrupts are missing, therefore this patch is to add MSI support to
ath9k.  With module paremeter "use_msi=1", ath9k driver would try to
use MSI instead of INTx.

Signed-off-by: Russell Hu <rhu@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ath/ath9k/hw.c

@@ -922,6 +922,7 @@ static void ath9k_hw_init_interrupt_masks(struct ath_hw *ah,
 		AR_IMR_RXERR |
 		AR_IMR_RXORN |
 		AR_IMR_BCNMISC;
+	u32 msi_cfg = 0;
 
 	if (AR_SREV_9340(ah) || AR_SREV_9550(ah) || AR_SREV_9531(ah) ||
 	    AR_SREV_9561(ah))
@@ -929,22 +930,30 @@ static void ath9k_hw_init_interrupt_masks(struct ath_hw *ah,
 
 	if (AR_SREV_9300_20_OR_LATER(ah)) {
 		imr_reg |= AR_IMR_RXOK_HP;
-		if (ah->config.rx_intr_mitigation)
+		if (ah->config.rx_intr_mitigation) {
 			imr_reg |= AR_IMR_RXINTM | AR_IMR_RXMINTR;
-		else
+			msi_cfg |= AR_INTCFG_MSI_RXINTM | AR_INTCFG_MSI_RXMINTR;
+		} else {
 			imr_reg |= AR_IMR_RXOK_LP;
-
+			msi_cfg |= AR_INTCFG_MSI_RXOK;
+		}
 	} else {
-		if (ah->config.rx_intr_mitigation)
+		if (ah->config.rx_intr_mitigation) {
 			imr_reg |= AR_IMR_RXINTM | AR_IMR_RXMINTR;
-		else
+			msi_cfg |= AR_INTCFG_MSI_RXINTM | AR_INTCFG_MSI_RXMINTR;
+		} else {
 			imr_reg |= AR_IMR_RXOK;
+			msi_cfg |= AR_INTCFG_MSI_RXOK;
+		}
 	}
 
-	if (ah->config.tx_intr_mitigation)
+	if (ah->config.tx_intr_mitigation) {
 		imr_reg |= AR_IMR_TXINTM | AR_IMR_TXMINTR;
-	else
+		msi_cfg |= AR_INTCFG_MSI_TXINTM | AR_INTCFG_MSI_TXMINTR;
+	} else {
 		imr_reg |= AR_IMR_TXOK;
+		msi_cfg |= AR_INTCFG_MSI_TXOK;
+	}
 
 	ENABLE_REGWRITE_BUFFER(ah);
 
@@ -952,6 +961,16 @@ static void ath9k_hw_init_interrupt_masks(struct ath_hw *ah,
 	ah->imrs2_reg |= AR_IMR_S2_GTT;
 	REG_WRITE(ah, AR_IMR_S2, ah->imrs2_reg);
 
+	if (ah->msi_enabled) {
+		ah->msi_reg = REG_READ(ah, AR_PCIE_MSI);
+		ah->msi_reg |= AR_PCIE_MSI_HW_DBI_WR_EN;
+		ah->msi_reg &= AR_PCIE_MSI_HW_INT_PENDING_ADDR_MSI_64;
+		REG_WRITE(ah, AR_INTCFG, msi_cfg);
+		ath_dbg(ath9k_hw_common(ah), ANY,
+			"value of AR_INTCFG=0x%X, msi_cfg=0x%X\n",
+			REG_READ(ah, AR_INTCFG), msi_cfg);
+	}
+
 	if (!AR_SREV_9100(ah)) {
 		REG_WRITE(ah, AR_INTR_SYNC_CAUSE, 0xFFFFFFFF);
 		REG_WRITE(ah, AR_INTR_SYNC_ENABLE, sync_default);