SPI DMA maximum message size

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SPI DMA maximum message size

Unread postby ban » Tue Jun 12, 2018 5:26 am

Hello.

I want to transfer a data with a size of >256KB in a single SPI message with DMA.
I'm using ODROID-XU4 with Ubuntu 18.04 LTS (GNU/Linux 4.14.43-138 armv7l).
I'm testing this with slightly modified spidev_test.c.
The DMA coherent_pool is 1MB by default:
Code: Select all
[    0.218410] DMA: preallocated 1024 KiB pool for atomic coherent allocations

I've set the spidev bufsiz to 512KB:
Code: Select all
rmmod spidev
modprobe spidev bufsiz=524288

When I try to send the SPI message with the size of 256KB then everything works fine.
But when I try to send the message with the size of >256KB then I'm getting an error:
Code: Select all
can't send spi message: Input/output error


Is it a hardware restriction of Exynos 5422 DMA or is there some other parameters that I need to change?
ban
 
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