From a194597c0cd35a7e8fc6386a717b56a653e3e0a0 Mon Sep 17 00:00:00 2001 From: "Jiri Slaby (SUSE)" Date: Wed, 11 Jun 2025 12:03:01 +0200 Subject: [PATCH] serial: 8250: extract serial8250_THRE_test() serial8250_do_startup() contains a stand-alone code for probing THRE. Furthermore, the code block is conditional (port->irq and test for UPF_NO_THRE_TEST). Move this code to a separate function. The conditional can be evaluated easier there -- by a simple return in the beginning. So the indentation level lowers and the code is overall more readable now. Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20250611100319.186924-16-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 92 +++++++++++++++-------------- 1 file changed, 49 insertions(+), 43 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index c09a90b38d8fc..5466286bb44fc 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2199,6 +2199,54 @@ static void serial8250_set_TRG_levels(struct uart_port *port) } } +static void serial8250_THRE_test(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + unsigned long flags; + bool iir_noint1, iir_noint2; + + if (!port->irq) + return; + + if (up->port.flags & UPF_NO_THRE_TEST) + return; + + if (port->irqflags & IRQF_SHARED) + disable_irq_nosync(port->irq); + + /* + * Test for UARTs that do not reassert THRE when the transmitter is idle and the interrupt + * has already been cleared. Real 16550s should always reassert this interrupt whenever the + * transmitter is idle and the interrupt is enabled. Delays are necessary to allow register + * changes to become visible. + * + * Synchronize UART_IER access against the console. + */ + uart_port_lock_irqsave(port, &flags); + + wait_for_xmitr(up, UART_LSR_THRE); + serial_port_out_sync(port, UART_IER, UART_IER_THRI); + udelay(1); /* allow THRE to set */ + iir_noint1 = serial_port_in(port, UART_IIR) & UART_IIR_NO_INT; + serial_port_out(port, UART_IER, 0); + serial_port_out_sync(port, UART_IER, UART_IER_THRI); + udelay(1); /* allow a working UART time to re-assert THRE */ + iir_noint2 = serial_port_in(port, UART_IIR) & UART_IIR_NO_INT; + serial_port_out(port, UART_IER, 0); + + uart_port_unlock_irqrestore(port, flags); + + if (port->irqflags & IRQF_SHARED) + enable_irq(port->irq); + + /* + * If the interrupt is not reasserted, or we otherwise don't trust the iir, setup a timer to + * kick the UART on a regular basis. + */ + if ((!iir_noint1 && iir_noint2) || up->port.flags & UPF_BUG_THRE) + up->bugs |= UART_BUG_THRE; +} + int serial8250_do_startup(struct uart_port *port) { struct uart_8250_port *up = up_to_u8250p(port); @@ -2258,49 +2306,7 @@ int serial8250_do_startup(struct uart_port *port) if (retval) goto out; - if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) { - unsigned char iir1; - - if (port->irqflags & IRQF_SHARED) - disable_irq_nosync(port->irq); - - /* - * Test for UARTs that do not reassert THRE when the - * transmitter is idle and the interrupt has already - * been cleared. Real 16550s should always reassert - * this interrupt whenever the transmitter is idle and - * the interrupt is enabled. Delays are necessary to - * allow register changes to become visible. - * - * Synchronize UART_IER access against the console. - */ - uart_port_lock_irqsave(port, &flags); - - wait_for_xmitr(up, UART_LSR_THRE); - serial_port_out_sync(port, UART_IER, UART_IER_THRI); - udelay(1); /* allow THRE to set */ - iir1 = serial_port_in(port, UART_IIR); - serial_port_out(port, UART_IER, 0); - serial_port_out_sync(port, UART_IER, UART_IER_THRI); - udelay(1); /* allow a working UART time to re-assert THRE */ - iir = serial_port_in(port, UART_IIR); - serial_port_out(port, UART_IER, 0); - - uart_port_unlock_irqrestore(port, flags); - - if (port->irqflags & IRQF_SHARED) - enable_irq(port->irq); - - /* - * If the interrupt is not reasserted, or we otherwise - * don't trust the iir, setup a timer to kick the UART - * on a regular basis. - */ - if ((!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) || - up->port.flags & UPF_BUG_THRE) { - up->bugs |= UART_BUG_THRE; - } - } + serial8250_THRE_test(port); up->ops->setup_timer(up); -- 2.51.0