linux-kernel - Re: [PATCH 03/16] tty: serial: 8250_core: read only RX if there is something in the FIFO

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Date:	Thu, 12 Feb 2015 21:34:37 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Peter Hurley <peter@...leysoftware.com>
CC:	Tony Lindgren <tony@...mide.com>,
	Nicolas Schichan <nschichan@...ebox.fr>,
	gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org, balbi@...com,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 03/16] tty: serial: 8250_core: read only RX if there is
 something in the FIFO

On 02/12/2015 08:55 PM, Peter Hurley wrote:
> On 02/12/2015 02:23 PM, Sebastian Andrzej Siewior wrote:
>> * Peter Hurley | 2015-02-12 11:32:04 [-0500]:
>>
>>> That said, I don't think serial8250_do_startup() is really doing that much
>>> for OMAP h/w startup; open-coding what omap_8250 really needs is probably
>>> < 10 loc.
>>
>> 10 loc? I have a few more.
> 
> :)
> 
>> serial8250_clear_fifos(),
>> serial_link_irq_chain() aren't exported. serial8250_set_mctrl() can
>> maybe accessed via uart_ops->set_mctrl(). Maybe I'm not removing the
>> obvious not required code but here it looks better to just a BUG flag for
>> the Omap.
> 
> Ok.

Okay. I will try to post something tomorrow.

>> --- a/drivers/tty/serial/8250/8250_omap.c
>> +++ b/drivers/tty/serial/8250/8250_omap.c
>> +
>> +	/*
>> +	 * Clear the interrupt registers.
>> +	 */
>> +	if (serial_port_in(port, UART_LSR) & UART_LSR_DR)
>> +		serial_port_in(port, UART_RX);
>> +	serial_port_in(port, UART_IIR);
>> +	serial_port_in(port, UART_MSR);
>> +
>> +	retval = serial_link_irq_chain(up);
>> +	if (retval)
>> +		goto out;
> 
> omap doesn't really need the legacy irq chain handling; this could just be
> request_irq().
> 
> In the 8250 split I'll be posting soon, all the irq chaining and
> polling-via-timeout workarounds stays in the universal/legacy driver so
> other 8250 drivers can opt-out.

Ah. This sounds interesting.

Sebastian
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