linux-kernel - [PATCH tty-next v1 1/4] serial: 8250: Use @ier bits to determine if Rx is stopped

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Message-Id: <20241216171244.12783-2-john.ogness@linutronix.de>
Date: Mon, 16 Dec 2024 18:18:41 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>,
	Esben Haabendal <esben@...nix.com>,
	linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	Rengarajan S <rengarajan.s@...rochip.com>,
	Bart Van Assche <bvanassche@....org>,
	Niklas Schnelle <schnelle@...ux.ibm.com>,
	Serge Semin <fancer.lancer@...il.com>,
	Lino Sanfilippo <l.sanfilippo@...bus.com>,
	Peter Collingbourne <pcc@...gle.com>
Subject: [PATCH tty-next v1 1/4] serial: 8250: Use @ier bits to determine if Rx is stopped

Commit f19c3f6c8109 ("serial: 8250_port: Don't service RX FIFO if
throttled") uses @read_status_mask (bit UART_LSR_DR) to determine
if Rx has been stopped. However, the bit UART_LSR_DR is not
managed properly in @read_status_mask for all Rx stop/start
situations and is therefore not suitable for this purpose.

Use the UART_IER_RLSI and UART_IER_RDI bits in @ier instead, as
this is already common in 8250-variants and drivers.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 drivers/tty/serial/8250/8250_port.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 1ea52fce9bf1..4d742bfb7e9a 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1931,7 +1931,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 	 */
 	if (!(status & (UART_LSR_FIFOE | UART_LSR_BRK_ERROR_BITS)) &&
 	    (port->status & (UPSTAT_AUTOCTS | UPSTAT_AUTORTS)) &&
-	    !(port->read_status_mask & UART_LSR_DR))
+	    !(up->ier & (UART_IER_RLSI | UART_IER_RDI)))
 		skip_rx = true;
 
 	if (status & (UART_LSR_DR | UART_LSR_BI) && !skip_rx) {
-- 
2.39.5