Re: [ECOS] JFFS2 sucess! (RE: [ECOS] JFFS2, for Redboot only?)

[Jonathan Larmour <jifl at eCosCentric dot com>]

Dirk Broer wrote:
> I modified flashiodev_init() to unlock the part of the flash that was in
> question.  Could someone suggest a better place?  The file in particular is
> in the ECOS distribution - seems wrong to modify it there.

At the start of your application before you call mount.

> One issue remains, since our device was never intended for constant reads
> and writes the flash is at address 0.  The problem is during writes we need
> to disable interrupts so that interrupt vector lookup won't happen.  Can't
> afford the time that a large flash write will take.  Seems the Intel flash
> driver has some provisions for a word by word write.  Essentially write a
> word, reset flash, read a word.  I think I can get away with bracketing
> this - need to ask the hardware guys about this.

You can only erase a page at a time, and that's one of the slowest 
operations - on some parts it can be about 1s.

Besides, you don't want to write word by word. I vaguely recall that 
programming a word doesn't take a very different time from programming a 
whole block.

> Could make the code generic:  If interrupt_vector_table is in active flash,
> disable interrupts during write/erase.

What CPU is this? Can you not remap the interrupt vector table or flash 
away from 0?

Or if you're prepared to change some of the cache manipulation code in the 
flash driver, you could lock the interrupt vector table into cache and 
leave the cache enabled. All depends on your CPU whether this is possible.

There's probably more answers to this if I thought about it more.

> So..... does JFFS2 buffer writes?  Any provision for async completion? 

It doesn't do either in eCos. Of course this can be solved by separating 
the I/O operations from the rest of the system in your application by doing 
I/O in different threads.

> Thanks Andrew Lunn and Gary Thomas

No offence to them, but thanks moreover to 3G Lab (now Trigenix) who did 
the initial eCos port.

Jifl
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