Messages in this thread | | | Date | Mon, 18 May 2020 18:19:28 +0300 | From | Andy Shevchenko <> | Subject | Re: [PATCH v3 4/5] serial: 8250: Handle implementations not having TEMT interrupt using em485 |
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On Sun, May 17, 2020 at 11:56:09PM +0200, Heiko Stuebner wrote: > From: Giulio Benetti <giulio.benetti@micronovasrl.com> > > Some 8250 ports have a TEMT interrupt but it's not a part of the 8250 > standard, instead only available on some implementations. > > The current em485 implementation does not work on ports without it. > The only chance to make it work is to loop-read on LSR register. > > So add UART_CAP_TEMT to mark 8250 uarts having this interrupt, > update all current em485 users with that capability and add > a loop-reading during __stop_tx_rs485() on uarts not having it. > > As __stop_tx_rs485() can also be called from a hard-irq context the > loop-reading is split. If the fifo clears in under 100us in > __stop_tx_rs485() itself just the regular stop calls get executed. > If it takes longer, re-use the existing stop-timer infrastructure > but with only a 10us timer to again poll the LSR registers. > > Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> [moved to use added UART_CAP_TEMT, use readx_poll_timeout]
I can't parse first part...
Also, shouldn't it be rather like [heiko: ...] ?
...
> +static inline int __get_lsr(struct uart_8250_port *p) > +{ > + return serial_in(p, UART_LSR); > +} > + > +static inline int __wait_for_empty(struct uart_8250_port *p, u64 timeout_us) > +{ > + int lsr; > + > + return readx_poll_timeout(__get_lsr, p, lsr, > + (lsr & BOTH_EMPTY) == BOTH_EMPTY, > + 0, timeout_us); > +}
...
> + int ret = __wait_for_empty(p, 100);
Do you expect something different than 100? If no, perhaps for now just put it inside the function as a constant?
> + if (ret < 0) { > + restart = HRTIMER_RESTART; > + goto out; > + }
...
> + } else if (!(p->capabilities & UART_CAP_TEMT) && > + __wait_for_empty(p, 100)) {
I would leave it on one line even if you leave 100 as a parameter, but it's up to you.
...
> + if (p->capabilities & UART_CAP_TEMT) { > + if ((lsr & BOTH_EMPTY) != BOTH_EMPTY) > + return; > + }
if (a) { if (b) { ... } }
is equivalent to
if (a && b) { ... }
But it's up to you which one to choose.
-- With Best Regards, Andy Shevchenko
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