linux-kernel - Re: Using serial driver 16550A in poll mode without interrupt connected

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Message-ID: <20111012145153.5490b592@lxorguk.ukuu.org.uk>
Date:	Wed, 12 Oct 2011 14:51:53 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	monstr@...str.eu
Cc:	linux-serial@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Korsgaard <jacmet@...site.dk>
Subject: Re: Using serial driver 16550A in poll mode without interrupt
 connected

> Driver is probed with no IRQ (NO_IRQ = -1 on Microblaze)
> 83e00000.serial: ttyS0 at MMIO 0x83e01003 (irq = -1) is a 16550A

Zero means no IRQ. NO_IRQ is a legacy internal thing for the old IDE code
so not something other code should be using. Setting the IRQ to -1 is
bogus and will confuse the rest of the kernel.

> Is it possible to use serial driver without IRQ - or blocking IRQ, etc.?

Within limits - it kills your power management and data rates because of
the continual polling.

Alan
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