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From:   Krishna Yarlagadda <kyarlagadda@nvidia.com>
To:     <gregkh@linuxfoundation.org>, <robh+dt@kernel.org>,
        <mark.rutland@arm.com>, <thierry.reding@gmail.com>,
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CC:     <linux-serial@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-tegra@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        "Shardar Shariff Md" <smohammed@nvidia.com>,
        Krishna Yarlagadda <kyarlagadda@nvidia.com>
Subject: [PATCH 02/14] serial: tegra: add support to ignore read
Date:   Mon, 12 Aug 2019 16:58:11 +0530
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From: Shardar Shariff Md <smohammed@nvidia.com>

Add support to ignore read characters if CREAD flag is not set.

Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>
Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
---
 drivers/tty/serial/serial-tegra.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 19f4c24..93d299e 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -542,6 +542,9 @@ static void tegra_uart_handle_rx_pio(struct tegra_uart_port *tup,
 		ch = (unsigned char) tegra_uart_read(tup, UART_RX);
 		tup->uport.icount.rx++;
 
+		if (tup->uport.ignore_status_mask & UART_LSR_DR)
+			continue;
+
 		if (!uart_handle_sysrq_char(&tup->uport, ch) && tty)
 			tty_insert_flip_char(tty, ch, flag);
 	} while (1);
@@ -562,6 +565,10 @@ static void tegra_uart_copy_rx_to_tty(struct tegra_uart_port *tup,
 		dev_err(tup->uport.dev, "No tty port\n");
 		return;
 	}
+
+	if (tup->uport.ignore_status_mask & UART_LSR_DR)
+		return;
+
 	dma_sync_single_for_cpu(tup->uport.dev, tup->rx_dma_buf_phys,
 				TEGRA_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE);
 	copied = tty_insert_flip_string(tty,
@@ -1190,6 +1197,11 @@ static void tegra_uart_set_termios(struct uart_port *u,
 	tegra_uart_write(tup, tup->ier_shadow, UART_IER);
 	tegra_uart_read(tup, UART_IER);
 
+	tup->uport.ignore_status_mask = 0;
+	/* Ignore all characters if CREAD is not set */
+	if ((termios->c_cflag & CREAD) == 0)
+		tup->uport.ignore_status_mask |= UART_LSR_DR;
+
 	spin_unlock_irqrestore(&u->lock, flags);
 }
 
-- 
2.7.4