* MPC512x SPI very high cpu load
@ 2008-11-19 15:26 Matteo Fortini
2008-11-20 19:39 ` Matt Sealey
0 siblings, 1 reply; 2+ messages in thread
From: Matteo Fortini @ 2008-11-19 15:26 UTC (permalink / raw)
To: linuxppc-embedded
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
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: MPC512x SPI very high cpu load
2008-11-19 15:26 MPC512x SPI very high cpu load Matteo Fortini
@ 2008-11-20 19:39 ` Matt Sealey
0 siblings, 0 replies; 2+ messages in thread
From: Matt Sealey @ 2008-11-20 19:39 UTC (permalink / raw)
To: Matteo Fortini; +Cc: linuxppc-embedded
Matteo Fortini wrote:
> 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.
If the SPI driver isn't using DMA then, it's not using DMA.
--
Matt Sealey <matt@genesi-usa.com>
Genesi, Manager, Developer Relations
^ permalink raw reply [flat|nested] 2+ messages in thread
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