[PATCH v4 3/4] serial: sh-sci: Resume PIO in sci_rx_interrupt() on DMA failure

From: Geert Uytterhoeven <geert+renesas@glider.be>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.com>
Cc: Ulrich Hecht <uli+renesas@fpond.eu>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	linux-renesas-soc@vger.kernel.org, linux-sh@vger.kernel.org,
	linux-serial@vger.kernel.org,
	Geert Uytterhoeven <geert+renesas@glider.be>
Subject: [PATCH v4 3/4] serial: sh-sci: Resume PIO in sci_rx_interrupt() on DMA failure
Date: Thu, 13 Dec 2018 19:44:43 +0100	[thread overview]
Message-ID: <20181213184444.21904-4-geert+renesas@glider.be> (raw)
In-Reply-To: <20181213184444.21904-1-geert+renesas@glider.be>

On (H)SCIF, sci_submit_rx() is called in the receive interrupt handler.
Hence if DMA submission fails, the interrupt handler should resume
handling reception using PIO, else no more data is received.

Make sci_submit_rx() return an error indicator, so the receive interrupt
handler can act appropriately.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v4:
  - Let sci_submit_rx() return -EAGAIN instead of -1 on failure,
  - Check for negative error in sci_submit_rx() caller,

v3:
  - Move label handle_pio inside #ifdef to kill defined but not used
    compiler warning when CONFIG_SERIAL_SH_SCI_DMA=n,
  - Move the call sci_submit_rx() in sci_rx_interrupt() up, as it may
    fail, rendering the modification of scr unused,
  - Split in multiple patches.
---
 drivers/tty/serial/sh-sci.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index e353e03ce2602559..8df0fd8245203f8b 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1331,7 +1331,7 @@ static void sci_tx_dma_release(struct sci_port *s)
 	dma_release_channel(chan);
 }
 
-static void sci_submit_rx(struct sci_port *s, bool port_lock_held)
+static int sci_submit_rx(struct sci_port *s, bool port_lock_held)
 {
 	struct dma_chan *chan = s->chan_rx;
 	struct uart_port *port = &s->port;
@@ -1359,7 +1359,7 @@ static void sci_submit_rx(struct sci_port *s, bool port_lock_held)
 	s->active_rx = s->cookie_rx[0];
 
 	dma_async_issue_pending(chan);
-	return;
+	return 0;
 
 fail:
 	/* Switch to PIO */
@@ -1374,6 +1374,7 @@ static void sci_submit_rx(struct sci_port *s, bool port_lock_held)
 	sci_start_rx(port);
 	if (!port_lock_held)
 		spin_unlock_irqrestore(&port->lock, flags);
+	return -EAGAIN;
 }
 
 static void work_fn_tx(struct work_struct *work)
@@ -1668,8 +1669,10 @@ static irqreturn_t sci_rx_interrupt(int irq, void *ptr)
 			disable_irq_nosync(irq);
 			scr |= SCSCR_RDRQE;
 		} else {
+			if (sci_submit_rx(s, false) < 0)
+				goto handle_pio;
+
 			scr &= ~SCSCR_RIE;
-			sci_submit_rx(s, false);
 		}
 		serial_port_out(port, SCSCR, scr);
 		/* Clear current interrupt */
@@ -1681,6 +1684,8 @@ static irqreturn_t sci_rx_interrupt(int irq, void *ptr)
 
 		return IRQ_HANDLED;
 	}
+
+handle_pio:
 #endif
 
 	if (s->rx_trigger > 1 && s->rx_fifo_timeout > 0) {
-- 
2.17.1

