From 47af7c8464a1f0cf9f86c37a411db5f774e34558 Mon Sep 17 00:00:00 2001
From: Sherry Sun <sherry.sun@nxp.com>
Date: Mon, 10 Jul 2023 09:38:57 +0800
Subject: [PATCH] tty: serial: fsl_lpuart: add IDLE interrupt support for
 rx_dma on imx7ulp/imx8ulp/imx8qxp

References: bsc#1214683 (PREEMPT_RT prerequisite backports)
Patch-mainline: v6.6-rc1
Git-commit: d9219528fab995c7cae79313867a8a92ee8e1f28

Add IDLE interrupt support for receive dma on imx7ulp/imx8ulp/imx8qxp
platforms to replace the receive dma timer function, because the receive
dma timer has bigger latency than idle interrupt triggering, which may
cause the Bluetooth Firmware download timeout on Android platform(it
has a limited FW download time window).

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20230710013857.7396-3-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 drivers/tty/serial/fsl_lpuart.c | 44 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index cf0047cd5d84..4175502b9460 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -288,6 +288,7 @@ struct lpuart_port {
 	wait_queue_head_t	dma_wait;
 	bool			is_cs7; /* Set to true when character size is 7 */
 					/* and the parity is enabled		*/
+	bool			dma_idle_int;
 };
 
 struct lpuart_soc_data {
@@ -1246,7 +1247,8 @@ static void lpuart_copy_rx_to_tty(struct lpuart_port *sport)
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 
 	tty_flip_buffer_push(port);
-	mod_timer(&sport->lpuart_timer, jiffies + sport->dma_rx_timeout);
+	if (!sport->dma_idle_int)
+		mod_timer(&sport->lpuart_timer, jiffies + sport->dma_rx_timeout);
 }
 
 static void lpuart_dma_rx_complete(void *arg)
@@ -1256,6 +1258,28 @@ static void lpuart_dma_rx_complete(void *arg)
 	lpuart_copy_rx_to_tty(sport);
 }
 
+static void lpuart32_dma_idleint(struct lpuart_port *sport)
+{
+	enum dma_status dmastat;
+	struct dma_chan *chan = sport->dma_rx_chan;
+	struct circ_buf *ring = &sport->rx_ring;
+	struct dma_tx_state state;
+	int count = 0;
+
+	dmastat = dmaengine_tx_status(chan, sport->dma_rx_cookie, &state);
+	if (dmastat == DMA_ERROR) {
+		dev_err(sport->port.dev, "Rx DMA transfer failed!\n");
+		return;
+	}
+
+	ring->head = sport->rx_sgl.length - state.residue;
+	count = CIRC_CNT(ring->head, ring->tail, sport->rx_sgl.length);
+
+	/* Check if new data received before copying */
+	if (count)
+		lpuart_copy_rx_to_tty(sport);
+}
+
 static irqreturn_t lpuart32_int(int irq, void *dev_id)
 {
 	struct lpuart_port *sport = dev_id;
@@ -1271,6 +1295,9 @@ static irqreturn_t lpuart32_int(int irq, void *dev_id)
 	if ((sts & UARTSTAT_TDRE) && !sport->lpuart_dma_tx_use)
 		lpuart32_txint(sport);
 
+	if ((sts & UARTSTAT_IDLE) && sport->lpuart_dma_rx_use && sport->dma_idle_int)
+		lpuart32_dma_idleint(sport);
+
 	lpuart32_write(&sport->port, sts, UARTSTAT);
 	return IRQ_HANDLED;
 }
@@ -1391,6 +1418,12 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport)
 		unsigned long temp = lpuart32_read(&sport->port, UARTBAUD);
 
 		lpuart32_write(&sport->port, temp | UARTBAUD_RDMAE, UARTBAUD);
+
+		if (sport->dma_idle_int) {
+			unsigned long ctrl = lpuart32_read(&sport->port, UARTCTRL);
+
+			lpuart32_write(&sport->port, ctrl | UARTCTRL_ILIE, UARTCTRL);
+		}
 	} else {
 		writeb(readb(sport->port.membase + UARTCR5) | UARTCR5_RDMAS,
 		       sport->port.membase + UARTCR5);
@@ -1406,7 +1439,9 @@ static void lpuart_dma_rx_free(struct uart_port *port)
 	struct dma_chan *chan = sport->dma_rx_chan;
 
 	dmaengine_terminate_sync(chan);
-	del_timer_sync(&sport->lpuart_timer);
+	if (!sport->dma_idle_int)
+		del_timer_sync(&sport->lpuart_timer);
+
 	dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE);
 	kfree(sport->rx_ring.buf);
 	sport->rx_ring.tail = 0;
@@ -1668,6 +1703,9 @@ static void lpuart32_setup_watermark_enable(struct lpuart_port *sport)
 
 static void rx_dma_timer_init(struct lpuart_port *sport)
 {
+	if (sport->dma_idle_int)
+		return;
+
 	timer_setup(&sport->lpuart_timer, lpuart_timer_func, 0);
 	sport->lpuart_timer.expires = jiffies + sport->dma_rx_timeout;
 	add_timer(&sport->lpuart_timer);
@@ -2824,6 +2862,8 @@ static int lpuart_probe(struct platform_device *pdev)
 	sport->port.type = PORT_LPUART;
 	sport->devtype = sdata->devtype;
 	sport->rx_watermark = sdata->rx_watermark;
+	sport->dma_idle_int = is_imx7ulp_lpuart(sport) || is_imx8ulp_lpuart(sport) ||
+			      is_imx8qxp_lpuart(sport);
 	ret = platform_get_irq(pdev, 0);
 	if (ret < 0)
 		return ret;