linux-kernel - [PATCH v2 04/16] serial: sc16is7xx: remove obsolete loop in sc16is7xx_port

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Message-Id: <20231221231823.2327894-5-hugo@hugovil.com>
Date: Thu, 21 Dec 2023 18:18:11 -0500
From: Hugo Villeneuve <hugo@...ovil.com>
To: gregkh@...uxfoundation.org,
	jirislaby@...nel.org,
	kubakici@...pl,
	indrakanti_ram@...mail.com,
	phil@...pberrypi.org
Cc: linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	hugo@...ovil.com,
	Hugo Villeneuve <hvilleneuve@...onoff.com>,
	stable@...r.kernel.org,
	Andy Shevchenko <andy.shevchenko@...il.com>
Subject: [PATCH v2 04/16] serial: sc16is7xx: remove obsolete loop in sc16is7xx_port_irq()

From: Hugo Villeneuve <hvilleneuve@...onoff.com>

Commit 834449872105 ("sc16is7xx: Fix for multi-channel stall") changed
sc16is7xx_port_irq() from looping multiple times when there was still
interrupts to serve. It simply changed the do {} while(1) loop to a
do {} while(0) loop, which makes the loop itself now obsolete.

Clean the code by removing this obsolete do {} while(0) loop.

Fixes: 834449872105 ("sc16is7xx: Fix for multi-channel stall")
Cc: stable@...r.kernel.org
Suggested-by: Andy Shevchenko <andy.shevchenko@...il.com>
Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
---
 drivers/tty/serial/sc16is7xx.c | 81 ++++++++++++++++------------------
 1 file changed, 39 insertions(+), 42 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index ced2446909a2..44a11c89c949 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -725,58 +725,55 @@ static void sc16is7xx_update_mlines(struct sc16is7xx_one *one)
 static bool sc16is7xx_port_irq(struct sc16is7xx_port *s, int portno)
 {
 	bool rc = true;
+	unsigned int iir, rxlen;
 	struct uart_port *port = &s->p[portno].port;
 	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 
 	mutex_lock(&one->efr_lock);
 
-	do {
-		unsigned int iir, rxlen;
+	iir = sc16is7xx_port_read(port, SC16IS7XX_IIR_REG);
+	if (iir & SC16IS7XX_IIR_NO_INT_BIT) {
+		rc = false;
+		goto out_port_irq;
+	}
 
-		iir = sc16is7xx_port_read(port, SC16IS7XX_IIR_REG);
-		if (iir & SC16IS7XX_IIR_NO_INT_BIT) {
-			rc = false;
-			goto out_port_irq;
-		}
+	iir &= SC16IS7XX_IIR_ID_MASK;
 
-		iir &= SC16IS7XX_IIR_ID_MASK;
+	switch (iir) {
+	case SC16IS7XX_IIR_RDI_SRC:
+	case SC16IS7XX_IIR_RLSE_SRC:
+	case SC16IS7XX_IIR_RTOI_SRC:
+	case SC16IS7XX_IIR_XOFFI_SRC:
+		rxlen = sc16is7xx_port_read(port, SC16IS7XX_RXLVL_REG);
 
-		switch (iir) {
-		case SC16IS7XX_IIR_RDI_SRC:
-		case SC16IS7XX_IIR_RLSE_SRC:
-		case SC16IS7XX_IIR_RTOI_SRC:
-		case SC16IS7XX_IIR_XOFFI_SRC:
-			rxlen = sc16is7xx_port_read(port, SC16IS7XX_RXLVL_REG);
+		/*
+		 * There is a silicon bug that makes the chip report a
+		 * time-out interrupt but no data in the FIFO. This is
+		 * described in errata section 18.1.4.
+		 *
+		 * When this happens, read one byte from the FIFO to
+		 * clear the interrupt.
+		 */
+		if (iir == SC16IS7XX_IIR_RTOI_SRC && !rxlen)
+			rxlen = 1;
 
-			/*
-			 * There is a silicon bug that makes the chip report a
-			 * time-out interrupt but no data in the FIFO. This is
-			 * described in errata section 18.1.4.
-			 *
-			 * When this happens, read one byte from the FIFO to
-			 * clear the interrupt.
-			 */
-			if (iir == SC16IS7XX_IIR_RTOI_SRC && !rxlen)
-				rxlen = 1;
-
-			if (rxlen)
-				sc16is7xx_handle_rx(port, rxlen, iir);
-			break;
+		if (rxlen)
+			sc16is7xx_handle_rx(port, rxlen, iir);
+		break;
 		/* CTSRTS interrupt comes only when CTS goes inactive */
-		case SC16IS7XX_IIR_CTSRTS_SRC:
-		case SC16IS7XX_IIR_MSI_SRC:
-			sc16is7xx_update_mlines(one);
-			break;
-		case SC16IS7XX_IIR_THRI_SRC:
-			sc16is7xx_handle_tx(port);
-			break;
-		default:
-			dev_err_ratelimited(port->dev,
-					    "ttySC%i: Unexpected interrupt: %x",
-					    port->line, iir);
-			break;
-		}
-	} while (0);
+	case SC16IS7XX_IIR_CTSRTS_SRC:
+	case SC16IS7XX_IIR_MSI_SRC:
+		sc16is7xx_update_mlines(one);
+		break;
+	case SC16IS7XX_IIR_THRI_SRC:
+		sc16is7xx_handle_tx(port);
+		break;
+	default:
+		dev_err_ratelimited(port->dev,
+				    "ttySC%i: Unexpected interrupt: %x",
+				    port->line, iir);
+		break;
+	}
 
 out_port_irq:
 	mutex_unlock(&one->efr_lock);
-- 
2.39.2