From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Heiko Stuebner <heiko@sntech.de>
Cc: gregkh@linuxfoundation.org, jslaby@suse.com,
matwey.kornilov@gmail.com, giulio.benetti@micronovasrl.com,
lukas@wunner.de, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org,
christoph.muellner@theobroma-systems.com,
Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Subject: Re: [PATCH v3 4/5] serial: 8250: Handle implementations not having TEMT interrupt using em485
Date: Mon, 18 May 2020 18:19:28 +0300 [thread overview]
Message-ID: <20200518151928.GH1634618@smile.fi.intel.com> (raw)
In-Reply-To: <20200517215610.2131618-5-heiko@sntech.de>
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
next prev parent reply other threads:[~2020-05-18 15:19 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-17 21:56 [PATCH v3 0/5] serial: 8250: Add rs485 emulation to 8250_dw Heiko Stuebner
2020-05-17 21:56 ` [PATCH v3 1/5] serial: 8520_port: Fix function param documentation Heiko Stuebner
2020-05-18 15:09 ` Andy Shevchenko
2020-05-17 21:56 ` [PATCH v3 2/5] dt-bindings: serial: Add binding for rs485 receiver enable GPIO Heiko Stuebner
2020-05-17 21:56 ` [PATCH v3 3/5] serial: 8250: Support separate rs485 rx-enable GPIO Heiko Stuebner
2020-05-18 4:50 ` Lukas Wunner
2020-05-18 8:04 ` Heiko Stübner
2020-05-18 9:19 ` Lukas Wunner
2020-05-18 15:12 ` Andy Shevchenko
2020-05-18 15:22 ` Lukas Wunner
2020-05-18 15:24 ` Lukas Wunner
2020-05-18 16:13 ` Maarten Brock
2020-05-18 16:35 ` Andy Shevchenko
2020-05-18 17:05 ` Maarten Brock
2020-05-18 17:16 ` Andy Shevchenko
2024-01-24 10:29 ` Farouk Bouabid
2020-05-17 21:56 ` [PATCH v3 4/5] serial: 8250: Handle implementations not having TEMT interrupt using em485 Heiko Stuebner
2020-05-18 15:19 ` Andy Shevchenko [this message]
2020-05-17 21:56 ` [PATCH v3 5/5] serial: 8250_dw: add em485 support Heiko Stuebner
2020-05-18 15:21 ` Andy Shevchenko
2021-02-02 0:31 ` Giulio Benetti
2021-02-02 11:22 ` Andy Shevchenko
2021-02-05 17:46 ` Giulio Benetti
2021-02-05 19:29 ` Andy Shevchenko
2022-09-22 9:56 ` [PATCH v3 0/5] serial: 8250: Add rs485 emulation to 8250_dw Lukas Wunner
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