Talk:DM816x C6A816x DEMMU Setup

Comments on DM816x C6A816x DEMMU Setup -

Ddanenberg said ...
This is my first try at using the MMU - I need it for accessing our external hardware. Based on the posted sample code, I am able to load and verify the MMU entries (CAM/RAM), but when I read the hardware, the contents are 0 (I verified its on-0 via another processor in 816). Also writing to the hardware does not change the register. I've tried a few variations - no success. Some questions/points. - In the static code posted, there is no enable in the MMU_CNTL reg. I tried enabling, still doesnt work, although I'm not sure what other bits should be set in MMU_CNTL for static operation. - I am also not sure about the use of the fields in MMU_RAM (eg, MIXED, or if i need translation). I've tried a few combinations - no luck. - The translation I need is like the example: the physical hardware I need to reach is at 0x08000000 - I use 0x11000000 as the virtual. - The hardware is organized in bytes.

Thanks -Dave

--Ddanenberg 14:10, 21 September 2011 (CDT)

Ddanenberg said ...
Posted my last comment too early. Looks like I was not enabling DSP MMU properly. My problem is different - more severe. Before trying to see if the GPMC MMU mapping works, the code crashes (code is fine if I leave MMU disabled). Seems the MMU is causing the program storage and/or stack areas to be in the wrong place. I have mapped the whole memory space within the CAM/RAM. I am still not certain which bits (ELEMENT_SIZE, et al) to set in MMU_RAM and MMU_CNTL. Thanks in advance for you help.

-Dave

--Ddanenberg 13:40, 22 September 2011 (CDT)