net: fec: add pm_qos support on imx6q platform

There is a very low probability that tx timeout will occur during
suspend and resume stress test on imx6q platform. So we add pm_qos
support to prevent system from entering low level idles which may
affect the transmission of tx.

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Link: https://lore.kernel.org/r/20220830070148.2021947-1-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/freescale/fec.h

@@ -16,6 +16,7 @@
 
 #include <linux/clocksource.h>
 #include <linux/net_tstamp.h>
+#include <linux/pm_qos.h>
 #include <linux/ptp_clock_kernel.h>
 #include <linux/timecounter.h>
 
@@ -498,6 +499,9 @@ struct bufdesc_ex {
 /* i.MX8MQ SoC integration mix wakeup interrupt signal into "int2" interrupt line. */
 #define FEC_QUIRK_WAKEUP_FROM_INT2	(1 << 22)
 
+/* i.MX6Q adds pm_qos support */
+#define FEC_QUIRK_HAS_PMQOS			BIT(23)
+
 struct bufdesc_prop {
 	int qid;
 	/* Address of Rx and Tx buffers */
@@ -608,6 +612,7 @@ struct fec_enet_private {
 	struct delayed_work time_keep;
 	struct regulator *reg_phy;
 	struct fec_stop_mode_gpr stop_gpr;
+	struct pm_qos_request pm_qos_req;
 
 	unsigned int tx_align;
 	unsigned int rx_align;

drivers/net/ethernet/freescale/fec_main.c

@@ -111,7 +111,8 @@ static const struct fec_devinfo fec_imx6q_info = {
 	.quirks = FEC_QUIRK_ENET_MAC | FEC_QUIRK_HAS_GBIT |
 		  FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM |
 		  FEC_QUIRK_HAS_VLAN | FEC_QUIRK_ERR006358 |
-		  FEC_QUIRK_HAS_RACC | FEC_QUIRK_CLEAR_SETUP_MII,
+		  FEC_QUIRK_HAS_RACC | FEC_QUIRK_CLEAR_SETUP_MII |
+		  FEC_QUIRK_HAS_PMQOS,
 };
 
 static const struct fec_devinfo fec_mvf600_info = {
@@ -3244,6 +3245,9 @@ fec_enet_open(struct net_device *ndev)
 	if (fep->quirks & FEC_QUIRK_ERR006687)
 		imx6q_cpuidle_fec_irqs_used();
 
+	if (fep->quirks & FEC_QUIRK_HAS_PMQOS)
+		cpu_latency_qos_add_request(&fep->pm_qos_req, 0);
+
 	napi_enable(&fep->napi);
 	phy_start(ndev->phydev);
 	netif_tx_start_all_queues(ndev);
@@ -3285,6 +3289,9 @@ fec_enet_close(struct net_device *ndev)
 	fec_enet_update_ethtool_stats(ndev);
 
 	fec_enet_clk_enable(ndev, false);
+	if (fep->quirks & FEC_QUIRK_HAS_PMQOS)
+		cpu_latency_qos_remove_request(&fep->pm_qos_req);
+
 	pinctrl_pm_select_sleep_state(&fep->pdev->dev);
 	pm_runtime_mark_last_busy(&fep->pdev->dev);
 	pm_runtime_put_autosuspend(&fep->pdev->dev);