Hi I am running Linux 2.6.10 on an MPC8260 target. We have an I2C controller that is part of our application code. In VxWorks, we could address the MPC8260 I2C memory registers directly from application space and so this was not a problem.
To port this same code to Linux, I am opening '/dev/mem' and mmapping the internal memory map of 128 KB to user space. I am writing directly to the I2C_BASE, I2C PRAM and I2C RxBD/TxBD registers, all of which are in DPRAM, from my application code through suitable macros. All of this is fine. I can see that the values have been written to memory if I do a memory dump of those registers with an external dump tool that uses '/dev/mem' too. Now, I have kept my Tx and Rx buffers in DPRAM as well, and have programmed those addresses in the buffer pointers of my TxBD and RxBDs. However, I am not sure if the values I'm writing to those locations from user space are actually being written to the actual memory locations. This is because I print the value of the first byte of my transmit buffer pointer BEFORE and AFTER I write the I2C address (0xA0 for us) to it. Before the address is written, the contents shown are 0x90. After it's written, the contents are shown rightly as 0xA0, but I don't think this value is actually written to DPRAM. This is because when I start I2C transmission by setting the start transfer bit in I2COM register, the address byte outputted on the I2C SDA bus is 0x90. This means it outputs the original value and not the value which I wrote to it. Can you suggest some kind of a "synchronization" function which I can call from *user space* which will ensure that all values written to mmaped memory locations from user space are actually flushed to their physical locations? I think this might be a potential problem with my code. Regards Vijay Padiyar http://www.vijaypadiyar.eu.tf
