Subject: MPC512x SPI very high cpu load

From: Matteo Fortini <[email-masked]>
Date: Wed, 19 Nov 2008 16:26:08 +0100

Hi,
we're using the latest denx tree on an mpc512x, and we have a 
touchscreen on the spi which is talking at 100kHz.

The polling frequency is 5ms and we transmit around 20 bytes per poll.

If we keep the touchscreen pressed, cpu utilization goes to 70% for the 
spi task. This is quite strange, since I thought the mpc512x would be 
using DMA to feed the PSC FIFOs.

Has anyone found the same problem? Should I lower the spi bandwidth?

Thank you,
Matteo