linux-kernel - [PATCH 4.19 056/113] serial: sh-sci: Terminate TX DMA during buffer flushing

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Message-Id: <20190729190708.903184110@linuxfoundation.org>
Date:   Mon, 29 Jul 2019 21:22:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 056/113] serial: sh-sci: Terminate TX DMA during buffer flushing

[ Upstream commit 775b7ffd7d6d5db320d99b0a485c51e04dfcf9f1 ]

While the .flush_buffer() callback clears sci_port.tx_dma_len since
commit 1cf4a7efdc71cab8 ("serial: sh-sci: Fix race condition causing
garbage during shutdown"), it does not terminate a transmit DMA
operation that may be in progress.

Fix this by terminating any pending DMA operations, and resetting the
corresponding cookie.

Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
Reviewed-by: Eugeniu Rosca <erosca@...adit-jv.com>
Tested-by: Eugeniu Rosca <erosca@...adit-jv.com>

Link: https://lore.kernel.org/r/20190624123540.20629-3-geert+renesas@glider.be
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/sh-sci.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 040832635a64..71f12601e693 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1633,11 +1633,18 @@ static void sci_free_dma(struct uart_port *port)
 
 static void sci_flush_buffer(struct uart_port *port)
 {
+	struct sci_port *s = to_sci_port(port);
+
 	/*
 	 * In uart_flush_buffer(), the xmit circular buffer has just been
-	 * cleared, so we have to reset tx_dma_len accordingly.
+	 * cleared, so we have to reset tx_dma_len accordingly, and stop any
+	 * pending transfers
 	 */
-	to_sci_port(port)->tx_dma_len = 0;
+	s->tx_dma_len = 0;
+	if (s->chan_tx) {
+		dmaengine_terminate_async(s->chan_tx);
+		s->cookie_tx = -EINVAL;
+	}
 }
 #else /* !CONFIG_SERIAL_SH_SCI_DMA */
 static inline void sci_request_dma(struct uart_port *port)
-- 
2.20.1