linux-kernel - FPGA Serial driver

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Date:	Tue, 20 Oct 2009 10:24:49 -0700
From:	"Jerry Johns" <Jerry.Johns@...ation.com>
To:	<linux-kernel@...r.kernel.org>
Subject: FPGA Serial driver

Hello all,
            I'm not exactly sure which mailing list to ask this, and am hoping that this list is the correct one for which this makes sense

I have an OMAP3530 mated to an FPGA over the GPMC interface (that maps external memory to a known linear space within the OMAP) found on that chip. I have an interrupt controller on the FPGA (and mapped into virtual IRQs in Linux through irqchip and chained handlers) and a few UARTs in it as well - the UART is specifically chosen to be 16550 compatible so that it can directly be mapped as a platform device into the 8250 serial platform driver. This way, I avoid having to write a serial driver, and it is directly compatible with that in Linux.

The FPGA currently is programmed by a separate device on boot, and that process can take up to 20 seconds - hence, the custom interrupt handler and serial driver in Linux cannot really be loaded until the FPGA has completed boot. At the same time, I do not want to hold-off booting Linux till the FPGA is alive.

What is the correct solution to this? Should I just load the interrupt and serial drivers anyways (and not use them till the FPGA is up) or should I defer loading them (that doesn't seem possible for the serial at least..)? 

Any ideas are much appreciated!

Thanks,
Jerry Johns
Design Engineer
Nuvation Research Corp - Canada

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