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serial: 8250: extract serial8250_THRE_test()

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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)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250611100319.186924-16-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby (SUSE) 2025-06-11 12:03:01 +02:00 committed by Greg Kroah-Hartman
parent cc852682f2
commit a194597c0c
1 changed files with 49 additions and 43 deletions
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92
drivers/tty/serial/8250/8250_port.c
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@ -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);