Nicolas, On Mon, Sep 03, 2007 at 05:23:40PM +0200, Nicolas TOUCHARD wrote: > I use ptxdist + oselas BSP for the Phytec PXA270. > > I need to have a real time SSP interrupt in 16 bit spi mode. > Sometimes, my SPI handler is delayed of 25µs to 170µs. It seen that is > the delay PXA Timer tick that can be itnerrupted (SA_INTERRUPT option > on the timer 0 handler). > > I suppose that that is due to the fact the kernel is only compile in > PREMPT and is not a true real time kernel , but 170µs seem to be very > long time for the timer interrupt ... > My kernel is is a Linux phyCORE-PXA270 2.6.17-pcm027-3 #3 PREEMPT > > Is-it normal that the irq PXA Timer tick can take up to 170µs? > > Can you advise me to patch the ptxdist / oselas PXA270 kernel to have > real time interrupt ?
On a normal system (non-rt), things can take as long as they like. 170 us is something which can happen. Even with rt, don't expect ARM cpus too have a too good realtime performance. We are currently preparing the next revision of the OSELAS.BSP für the phyCORE-PXA270, with rt-preempt, which will be based on 2.6.23-rt. Please tell me if you can't wait for that release (in that case we'd have to find another agreement). Regards, Robert -- Pengutronix - Linux Solutions for Science and Industry Entwicklungszentrum Nord http://www.pengutronix.de -- ptxdist mailing list ptxdist@pengutronix.de
