On 08:06 Fri 31 Oct , Jerry Van Baren wrote:
Wolfgang Denk wrote:
Dear rajeev s,
In message 843260.87725.qm@web50008.mail.re2.yahoo.com you wrote:
We have a custom board based on coldfire (MCF5484) Similar to MCF5484 Kitlite The board runs Coldfire as PCI agent , 64MB of SDRAM, 4 MB of Bootflash and the PCI bus as a slave (no serial port->no console) I can flash U-boot using the JTAG . Can you let know how can i pass the Commands over PCI . I do not have a Console to do that ?
Well, somebody who designed this system must also have had some plan how to operate the board?
Not having a console port sounds like a really stupid thing to me.
If you have ethenret on your board, you can try netconsole. But it will be no fun to port U-Boot to such hardware.
I suggest you bring the board back to the hardware guys and ask for a serial console port, at least for bring-up and debugging.
Best regards,
Wolfgang Denk
On the u-boot side, you can write a "fake uart" that... TX: Takes bytes and puts them in a "TX" queue in shared PCI memory. RX: Looks at the "RX" queue in shared PCI memory for new characters.
Then on the host side, you write a custom fake uart driver to do the opposite (taking advantage of the OS's capabilities and support programs) or write a custom terminal program that implements the fake uart handling directly (simpler to get running, much less flexible and more maintenance long term).
The queue can be a simple /n/ byte array (I would set /n/ to 256 or some larger power of 2 since size doesn't matter ;-) with head and tail indexes. The writer puts a byte in queue[head++] and the reader checks "if (head != tail) return queue[tail++]". Note that there is only one writer to "head" and one to "tail" so you don't have any race condition/locking issues (assuming your r/w access is atomic and you don't code any bugs into your algorithm).
Details glossed over:
- head and tail must be incremented modulo the queue length
- You *NEVER* want to set head or tail to be equal to the queue length in the shared memory (that would be out-of-bounds on the array). "head = (head + 1) % sizeof(queue);" should be save (check the assembly code, compiled with optimization!). If you use "head = ++head % sizeof(queue);", the compiler will write head++ with with wrong value 256 every 256 bytes (see the next bullet) and then do the modulo and re-write head with the correct value (0).
- You need to make all the shared variables "volatile"
- You need to prevent head from overtaking tail. For instance, if (head + 1) == tail (check *before* writing the byte to the queue), you have an overflow condition and will have to drop the byte.
I have not googled, I'm sure many people have done this before. Maybe you will get lucky and someone will have published source under a GPL (compatible) license.
IIRC I've seen this in the Prism54 driver
Best Regards, J.