wfx: avoid flush_workqueue(system_highpri_wq) usage

Flushing system-wide workqueues is dangerous and will be forbidden.
Replace system_highpri_wq with per "struct wfx_dev" bh_wq.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/f15574a6-aba4-72bc-73af-26fdcdf9fb63@I-love.SAKURA.ne.jp

drivers/net/wireless/silabs/wfx/bh.c

@@ -267,7 +267,7 @@ void wfx_bh_request_rx(struct wfx_dev *wdev)
 	wfx_control_reg_read(wdev, &cur);
 	prev = atomic_xchg(&wdev->hif.ctrl_reg, cur);
 	complete(&wdev->hif.ctrl_ready);
-	queue_work(system_highpri_wq, &wdev->hif.bh);
+	queue_work(wdev->bh_wq, &wdev->hif.bh);
 
 	if (!(cur & CTRL_NEXT_LEN_MASK))
 		dev_err(wdev->dev, "unexpected control register value: length field is 0: %04x\n",
@@ -280,7 +280,7 @@ void wfx_bh_request_rx(struct wfx_dev *wdev)
 /* Driver want to send data */
 void wfx_bh_request_tx(struct wfx_dev *wdev)
 {
-	queue_work(system_highpri_wq, &wdev->hif.bh);
+	queue_work(wdev->bh_wq, &wdev->hif.bh);
 }
 
 /* If IRQ is not available, this function allow to manually poll the control register and simulate
@@ -295,7 +295,7 @@ void wfx_bh_poll_irq(struct wfx_dev *wdev)
 	u32 reg;
 
 	WARN(!wdev->poll_irq, "unexpected IRQ polling can mask IRQ");
-	flush_workqueue(system_highpri_wq);
+	flush_workqueue(wdev->bh_wq);
 	start = ktime_get();
 	for (;;) {
 		wfx_control_reg_read(wdev, &reg);

drivers/net/wireless/silabs/wfx/hif_tx.c

@@ -73,7 +73,7 @@ int wfx_cmd_send(struct wfx_dev *wdev, struct wfx_hif_msg *request,
 
 	if (no_reply) {
 		/* Chip won't reply. Ensure the wq has send the buffer before to continue. */
-		flush_workqueue(system_highpri_wq);
+		flush_workqueue(wdev->bh_wq);
 		ret = 0;
 		goto end;
 	}

drivers/net/wireless/silabs/wfx/main.c

@@ -345,6 +345,10 @@ int wfx_probe(struct wfx_dev *wdev)
 	wdev->pdata.gpio_wakeup = NULL;
 	wdev->poll_irq = true;
 
+	wdev->bh_wq = alloc_workqueue("wfx_bh_wq", WQ_HIGHPRI, 0);
+	if (!wdev->bh_wq)
+		return -ENOMEM;
+
 	wfx_bh_register(wdev);
 
 	err = wfx_init_device(wdev);
@@ -458,6 +462,7 @@ int wfx_probe(struct wfx_dev *wdev)
 	wdev->hwbus_ops->irq_unsubscribe(wdev->hwbus_priv);
 bh_unregister:
 	wfx_bh_unregister(wdev);
+	destroy_workqueue(wdev->bh_wq);
 	return err;
 }
 
@@ -467,6 +472,7 @@ void wfx_release(struct wfx_dev *wdev)
 	wfx_hif_shutdown(wdev);
 	wdev->hwbus_ops->irq_unsubscribe(wdev->hwbus_priv);
 	wfx_bh_unregister(wdev);
+	destroy_workqueue(wdev->bh_wq);
 }
 
 static int __init wfx_core_init(void)

drivers/net/wireless/silabs/wfx/wfx.h

@@ -57,6 +57,7 @@ struct wfx_dev {
 	struct mutex               rx_stats_lock;
 	struct wfx_hif_tx_power_loop_info tx_power_loop_info;
 	struct mutex               tx_power_loop_info_lock;
+	struct workqueue_struct    *bh_wq;
 };
 
 struct wfx_vif {