How to exploit STS pin of Strata Flash

[llandre]

>My biggest concern is this STS pin is not something supported on many
>strataflash chips.   Though this might be an elegant solution for a
>system with irq lines to spare using these particular chips I don't
>think it would be used often enough to be supportable.

I see. So far I worked with Intel StrataFlash only.

> > I don't know how NOR/Strata Flash drivers work and I thouhgt they implement
> > the well-known data polling algorithm to detect the end of operation.
> > However, if they actually "sleeps" as you pointed out, I
> > clearly am wrong. If I'm right instead, the data-polling algorithm wastes
> > bandwidth
> > because it performs a lot of read accesses just to read the value of a bit.
>
>in 2.6.10 drivers/mtd/chips/
>cfi_cmdset_0001.c:1065  sleeps for the word write if I understand
>cfi_udelay() correctly
>cfi_cmdset_0001.c:1308  sleeps for the buffered write if I understand
>cfi_udelay() correctly
>cfi_cmdset_0001.c:1470  sleeps for the erase

Ok, so I was wrong.

> > This can lead to problems for example when you have a bus-demanding
> > peripheral such
> > as a LCD controller. In this case the wasted bandwith can lead to 
> flickering.
> > In conclusion, to avoid data-polling algorithm, it is possible to 
> implement the
> > same ready/busy pin strategy used for NAND chips.
>
>I can imagine that happens, but does it?  I'm never been able to see
>that kind of effect, have you?

Yes, I have encountered this problem with a Frescale MC9328MXL processor.
The flickering occurs when JFFS2 performs erase/write operations on the
StrataFlash. This happens with Linux 2.6 only. When running
Linux 2.4 LCD exhibits no flickering.




llandre

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