linux-kernel - [PATCH 1/3] tty/serial: atmel: re-integrate status check in irq handler

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Date:	Thu, 12 May 2016 17:37:34 +0200
From:	Ludovic Desroches <ludovic.desroches@...el.com>
To:	<nicolas.ferre@...el.com>, <gregkh@...uxfoundation.org>
CC:	<jslaby@...e.com>, <linux-serial@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Ludovic Desroches <ludovic.desroches@...el.com>
Subject: [PATCH 1/3] tty/serial: atmel: re-integrate status check in irq handler

From: Nicolas Ferre <nicolas.ferre@...el.com>

The IRQ status check and related actions was done in the tasklet without
benefit. So, move it back to the IRQ context to simplify IRQ handling and
having the possibility to split the tasklet in two separated ones for
receive and transmit actions.

Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
---
 drivers/tty/serial/atmel_serial.c | 43 ++++++++++++++++-----------------------
 1 file changed, 17 insertions(+), 26 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 954941d..8854ac6 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -146,9 +146,7 @@ struct atmel_uart_port {
 	struct scatterlist		sg_tx;
 	struct scatterlist		sg_rx;
 	struct tasklet_struct	tasklet;
-	unsigned int		irq_status;
 	unsigned int		irq_status_prev;
-	unsigned int		status_change;
 	unsigned int		tx_len;
 
 	struct circ_buf		rx_ring;
@@ -1237,14 +1235,27 @@ atmel_handle_status(struct uart_port *port, unsigned int pending,
 		    unsigned int status)
 {
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+	unsigned int status_change;
 
 	if (pending & (ATMEL_US_RIIC | ATMEL_US_DSRIC | ATMEL_US_DCDIC
 				| ATMEL_US_CTSIC)) {
-		atmel_port->irq_status = status;
-		atmel_port->status_change = atmel_port->irq_status ^
-					    atmel_port->irq_status_prev;
+		status_change = status ^ atmel_port->irq_status_prev;
 		atmel_port->irq_status_prev = status;
-		tasklet_schedule(&atmel_port->tasklet);
+
+		if (status_change & (ATMEL_US_RI | ATMEL_US_DSR
+					| ATMEL_US_DCD | ATMEL_US_CTS)) {
+			/* TODO: All reads to CSR will clear these interrupts! */
+			if (status_change & ATMEL_US_RI)
+				port->icount.rng++;
+			if (status_change & ATMEL_US_DSR)
+				port->icount.dsr++;
+			if (status_change & ATMEL_US_DCD)
+				uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
+			if (status_change & ATMEL_US_CTS)
+				uart_handle_cts_change(port, !(status & ATMEL_US_CTS));
+
+			wake_up_interruptible(&port->state->port.delta_msr_wait);
+		}
 	}
 }
 
@@ -1575,31 +1586,12 @@ static void atmel_tasklet_func(unsigned long data)
 {
 	struct uart_port *port = (struct uart_port *)data;
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
-	unsigned int status = atmel_port->irq_status;
-	unsigned int status_change = atmel_port->status_change;
 
 	/* The interrupt handler does not take the lock */
 	spin_lock(&port->lock);
 
 	atmel_port->schedule_tx(port);
 
-	if (status_change & (ATMEL_US_RI | ATMEL_US_DSR
-				| ATMEL_US_DCD | ATMEL_US_CTS)) {
-		/* TODO: All reads to CSR will clear these interrupts! */
-		if (status_change & ATMEL_US_RI)
-			port->icount.rng++;
-		if (status_change & ATMEL_US_DSR)
-			port->icount.dsr++;
-		if (status_change & ATMEL_US_DCD)
-			uart_handle_dcd_change(port, !(status & ATMEL_US_DCD));
-		if (status_change & ATMEL_US_CTS)
-			uart_handle_cts_change(port, !(status & ATMEL_US_CTS));
-
-		wake_up_interruptible(&port->state->port.delta_msr_wait);
-
-		atmel_port->status_change = 0;
-	}
-
 	atmel_port->schedule_rx(port);
 
 	spin_unlock(&port->lock);
@@ -1833,7 +1825,6 @@ static int atmel_startup(struct uart_port *port)
 
 	/* Save current CSR for comparison in atmel_tasklet_func() */
 	atmel_port->irq_status_prev = atmel_get_lines_status(port);
-	atmel_port->irq_status = atmel_port->irq_status_prev;
 
 	/*
 	 * Finally, enable the serial port
-- 
2.5.0