linux-kernel - Re: 8250 regression: infinite interrupts

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Message-ID: <CACRpkdZkwgZimCi_tH_CHd_JUi1YTKgSBK4VR9c5PPVq0Y+Ldg@mail.gmail.com>
Date:	Sat, 28 Jan 2012 11:50:44 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	philippe.langlais@...ricsson.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>, Greg KH <gregkh@...e.de>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org
Subject: Re: 8250 regression: infinite interrupts

2012/1/27 Jiri Slaby <jslaby@...e.cz>:

> The culprit is the added size_fifo call proper in autoconfig_16550a. It
> returns 16, but the chip is confused by what the function does at that
> point. It is yet to be investigated why. Any ideas at this stage why
> this could be a problem?

The header says the function sometimes fail :-/

What it does is set the UART in loopback mode and saturate it with
256 bytes to overflow the FIFO, then check how many chars
were in the FIFO to determine FIFO size.

Could it be that your variant does not clear the FIFO overflow
correctly and get stuck in some error state? Maybe try clearing
some error flags at the end of this function?

Yours,
Linus Walleij
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