mailbox: mediatek: implement flush function

For client driver which need to reorganize the command buffer, it could
use this function to flush the send command buffer.
If the channel doesn't be started (usually in waiting for event), this
function will abort it directly.
Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/mtk-cmdq-mailbox.c

@@ -432,10 +432,62 @@ static void cmdq_mbox_shutdown(struct mbox_chan *chan)
 {
 }
 
+static int cmdq_mbox_flush(struct mbox_chan *chan, unsigned long timeout)
+{
+	struct cmdq_thread *thread = (struct cmdq_thread *)chan->con_priv;
+	struct cmdq_task_cb *cb;
+	struct cmdq_cb_data data;
+	struct cmdq *cmdq = dev_get_drvdata(chan->mbox->dev);
+	struct cmdq_task *task, *tmp;
+	unsigned long flags;
+	u32 enable;
+
+	spin_lock_irqsave(&thread->chan->lock, flags);
+	if (list_empty(&thread->task_busy_list))
+		goto out;
+
+	WARN_ON(cmdq_thread_suspend(cmdq, thread) < 0);
+	if (!cmdq_thread_is_in_wfe(thread))
+		goto wait;
+
+	list_for_each_entry_safe(task, tmp, &thread->task_busy_list,
+				 list_entry) {
+		cb = &task->pkt->async_cb;
+		if (cb->cb) {
+			data.sta = CMDQ_CB_ERROR;
+			data.data = cb->data;
+			cb->cb(data);
+		}
+		list_del(&task->list_entry);
+		kfree(task);
+	}
+
+	cmdq_thread_resume(thread);
+	cmdq_thread_disable(cmdq, thread);
+	clk_disable(cmdq->clock);
+
+out:
+	spin_unlock_irqrestore(&thread->chan->lock, flags);
+	return 0;
+
+wait:
+	cmdq_thread_resume(thread);
+	spin_unlock_irqrestore(&thread->chan->lock, flags);
+	if (readl_poll_timeout_atomic(thread->base + CMDQ_THR_ENABLE_TASK,
+				      enable, enable == 0, 1, timeout)) {
+		dev_err(cmdq->mbox.dev, "Fail to wait GCE thread 0x%x done\n",
+			(u32)(thread->base - cmdq->base));
+
+		return -EFAULT;
+	}
+	return 0;
+}
+
 static const struct mbox_chan_ops cmdq_mbox_chan_ops = {
 	.send_data = cmdq_mbox_send_data,
 	.startup = cmdq_mbox_startup,
 	.shutdown = cmdq_mbox_shutdown,
+	.flush = cmdq_mbox_flush,
 };
 
 static struct mbox_chan *cmdq_xlate(struct mbox_controller *mbox,