Re: [PATCH 15/33] serial: 8250: extract serial8250_THRE_test()

Ilpo Järvinen
2025-06-12T09:18:45Z

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On Thu, 12 Jun 2025, Jiri Slaby wrote:

> On 11. 06. 25, 14:03, Ilpo Järvinen wrote:
> > On Wed, 11 Jun 2025, Jiri Slaby (SUSE) wrote:
> ...
> > > + /*
> > > + * 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.
> >
> > Very long comment lines are hard to read. (This is mostly not related to
> > line length limits, but with eye movement required.)
> >
> > It may make sense to place some of the descriptive comment text into a
> > function comment instead of placing them mid-function.
> >
> > > + *
> > > + * 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 */
> >
> > These comments mix visually into the code making this look a big wall of
> > text overall. Maybe consider adding empty lines to the logic as well as
> > there are what looks clear steps in this logic.
>
>
> What about this:
> > /*
> > * 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.
> > */
> > 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);
> > /* 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);
> > /* allow THRE to set */
> > udelay(1);
> > 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);
> > /* allow a working UART time to re-assert THRE */
> > udelay(1);
> > 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;
> > }
> >
>
> ?

I don't know what part exactly you wanted to ask about but it looks mostly
fine (sans what is broken due to email).

--
i.