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

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Message-ID: <54DCD584.3010500@hurleysoftware.com>
Date:	Thu, 12 Feb 2015 11:32:04 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
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 03:45 AM, Sebastian Andrzej Siewior wrote:
> On 02/11/2015 09:42 PM, Peter Hurley wrote:
> 
>>> Reverting makes sense to me if it has caused a regression. Maybe Sebastian
>>> can update his patch to do this based on some quirk flag instead?
>>
>> That's fine with me. There's a 'bugs' field in struct 8250_uart_port and
>> UART_BUG_* defines in 8250/8250.h for that purpose.
> 
> Makes sense. Reading an empty FIFO does not look right. Maybe we should
> do the bug flag the other way around? But I can do what I am told to so
> if there is more fallout than just this Marvell UART I could come
> around with a patch to the bug field for the older OMAP.

I agree with Russell on this; better to stick with the rx read that's been
running on 20 years of hardware.

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.

Regards,
Peter Hurley


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