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Date:   Mon, 30 Mar 2020 17:52:39 +0300
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, linux-serial@vger.kernel.org,
        linux-kernel@vger.kernel.org, lukas@wunner.de,
        christoph.muellner@theobroma-systems.com,
        giulio.benetti@micronovasrl.com,
        Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Subject: Re: [PATCH v2 4/7] serial: 8250: Handle implementations not having
 TEMT interrupt using em485
Message-ID: <20200330145239.GV1922688@smile.fi.intel.com>
References: <20200325231422.1502366-1-heiko@sntech.de>
 <20200325231422.1502366-5-heiko@sntech.de>
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On Thu, Mar 26, 2020 at 12:14:19AM +0100, 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 make
> the stop_tx function loop-read on uarts not having it.

> +		if (p->capabilities & UART_CAP_TEMT) {
> +			if ((lsr & BOTH_EMPTY) != BOTH_EMPTY)
> +				return;
> +		} else {
> +			int lsr;
> +

> +			if (readx_poll_timeout(__get_lsr, p, lsr,
> +					(lsr & BOTH_EMPTY) == BOTH_EMPTY,
> +					0, 10000) < 0)

			ret = readx_poll_timeout(...);
			if (ret)
				...

will look better.

> +				pr_warn("%s: timeout waiting for fifos to empty\n",
> +					p->port.name);
> +		}

-- 
With Best Regards,
Andy Shevchenko