[Gumstix-users] timer FIQ and CONFIG_FIQ

[ecrespin <eli...@gm...>]

Hello,

I have a working dmtimer based interrupt timer handler. I use it to send
time synchronized commands to a stepper motor driver connected to the Overo
through the SPI1 interface. This way the software can control the direction,
speed and moment in time of the motor movement. It works nicely and in
general very smoothly.

I am using an Overo Air with linux 2.6.33 from sakoman, generated with
bitbake overo-console-image and then modified with bitbake -c rebuild
linux-omap3-2.6.33.

The problem: 
If I generate load in the Overo while moving the motor (i.e. send a tcp
request to the overo or find a file on all of the Overo's file system) the
motor flickers and the smoothness of the motor's movement is affected.My
requirement is to be able to have the motor run smoothly even under these
load conditions on the Overo.

I have solved this in the past on the Verdex platform by using a FIQ based
timer to give the timer interrupt the highest priority and avoid being left
waiting for processor which is what generates the flickering. It worked very
well. This code was based on the pxaRC code published 
http://www.pabr.org/pxarc/doc/pxarc.en.html here  by Pascal.

That is why I am going for a FIQ timer on the Overo and I am stuck. I
studied the fiq based drivers in spi_s3c24xx.c and mx1_camera.c in the overo
linux sources. They seem good references for what I want to do with timer,
nevertheless, this examples require the fiq module to be configured into the
kernel which I will need for my fiq timer as well. By looking at the
Makefiles, the kernel option to install the fiq module is CONFIG_FIQ, but I
can not find it or set it. I tried appending it into defconfig or through
bitbake -c menuconfig linux-omap3-2.6.33 and the option does not appear or
is never set and thus the fiq module does not get compiled.

Is someone in the forum able to give me steps on how to activate the fiq
kernel option ? Does someone have a copy of fiq based timer code that is
willing to share with all of us ?

Thank you very much

Elias




-- 
View this message in context: http://old.nabble.com/timer-FIQ-and-CONFIG_FIQ-tp29235157p29235157.html
Sent from the Gumstix mailing list archive at Nabble.com.