serial: 8250: extract serial8250_iir_txen_test()

After commit 795158691cc0 ("serial: 8250: extract
serial8250_initialize()"), split serial8250_initialize() even more --
the TX enable test part of this code can be separated into
serial8250_iir_txen_test().

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Suggested-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250624080641.509959-3-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 0f85a2f292fc6aa9ffd59415b3bb642f5ad5f331..5bb0ca04da55f24cb51873243fe30ff7c37aedad 100644 (file)
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2230,16 +2230,19 @@ static void serial8250_init_mctrl(struct uart_port *port)
        serial8250_set_mctrl(port, port->mctrl);
 }
 
-static void serial8250_initialize(struct uart_port *port)
+static void serial8250_iir_txen_test(struct uart_port *port)
 {
        struct uart_8250_port *up = up_to_u8250p(port);
-       unsigned long flags;
        bool lsr_TEMT, iir_NOINT;
 
-       serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
+       if (port->quirks & UPQ_NO_TXEN_TEST)
+               return;
 
-       uart_port_lock_irqsave(port, &flags);
-       serial8250_init_mctrl(port);
+       /* Do a quick test to see if we receive an interrupt when we enable the TX irq. */
+       serial_port_out(port, UART_IER, UART_IER_THRI);
+       lsr_TEMT = serial_port_in(port, UART_LSR) & UART_LSR_TEMT;
+       iir_NOINT = serial_port_in(port, UART_IIR) & UART_IIR_NO_INT;
+       serial_port_out(port, UART_IER, 0);
 
        /*
         * Serial over Lan (SoL) hack:
@@ -2247,26 +2250,30 @@ static void serial8250_initialize(struct uart_port *port)
         * Lan.  Those chips take a longer time than a normal serial device to signalize that a
         * transmission data was queued. Due to that, the above test generally fails. One solution
         * would be to delay the reading of iir. However, this is not reliable, since the timeout is
-        * variable. So, let's just don't test if we receive TX irq.  This way, we'll never enable
-        * UART_BUG_TXEN.
+        * variable. So, in case of UPQ_NO_TXEN_TEST, let's just don't test if we receive TX irq.
+        * This way, we'll never enable UART_BUG_TXEN.
         */
-       if (!(port->quirks & UPQ_NO_TXEN_TEST)) {
-               /* Do a quick test to see if we receive an interrupt when we enable the TX irq. */
-               serial_port_out(port, UART_IER, UART_IER_THRI);
-               lsr_TEMT = serial_port_in(port, UART_LSR) & UART_LSR_TEMT;
-               iir_NOINT = serial_port_in(port, UART_IIR) & UART_IIR_NO_INT;
-               serial_port_out(port, UART_IER, 0);
-
-               if (lsr_TEMT && iir_NOINT) {
-                       if (!(up->bugs & UART_BUG_TXEN)) {
-                               up->bugs |= UART_BUG_TXEN;
-                               dev_dbg(port->dev, "enabling bad tx status workarounds\n");
-                       }
-               } else {
-                       up->bugs &= ~UART_BUG_TXEN;
+       if (lsr_TEMT && iir_NOINT) {
+               if (!(up->bugs & UART_BUG_TXEN)) {
+                       up->bugs |= UART_BUG_TXEN;
+                       dev_dbg(port->dev, "enabling bad tx status workarounds\n");
                }
+               return;
        }
 
+       /* FIXME: why is this needed? */
+       up->bugs &= ~UART_BUG_TXEN;
+}
+
+static void serial8250_initialize(struct uart_port *port)
+{
+       unsigned long flags;
+
+       serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
+
+       uart_port_lock_irqsave(port, &flags);
+       serial8250_init_mctrl(port);
+       serial8250_iir_txen_test(port);
        uart_port_unlock_irqrestore(port, flags);
 }