[ECOS] Possible typo in hal/arm/arm9/var/current/include/hal_cache.h

Gary D. Thomas gary.thomas@mind.be
Tue Jan 7 20:24:00 GMT 2003


On Tue, 2003-01-07 at 13:17, Jonathan Larmour wrote:
> Patrick Doyle wrote:
> > Can somebody (jskov perhaps, since your name is in the ChangeLog)
> 
> I'm not sure Jesper still reads ecos-discuss. I think he doesn't any more 
> unfortunately.
> 
> > tell me
> > the source of the data for the ARM925T cache configuration?  I am asking
> > because the #defines in this file don't match the documentation I have from
> > TI.  I will ask TI as well, but in the mean time, here is what the file
> > says:
> > 
> > # define HAL_ICACHE_SIZE                 0x4000
> > # define HAL_ICACHE_LINE_SIZE            32
> > # define HAL_ICACHE_WAYS                 2
> > # define HAL_ICACHE_SETS
> > (HAL_ICACHE_SIZE/(HAL_ICACHE_LINE_SIZE*HAL_ICACHE_WAYS))
> > 
> > And here is what the TI documentation (somewhat ambiguously) says:
> > 
> > "The 16K-byte instruction cache (I-cache) has 1024 lines of 16 bytes
> > arranged as a two-way set-associative cache."
> 
> I notice hal_arm_arm9.cdl says:
>              The ARM925T has 8k data cache, 16k instruction cache, 16 word
>              write buffer and an MMU."
> 
> > These two pieces of information clearly differ in the definition of the line
> > size.  Also, my first read of the TI documentation made me think there were
> > 1024 lines in each set, but the math doesn't work out for that.  Instead, I
> > think there are 1024 lines total, 512 in each set.  Regardless, these don't
> > match the 256 sets defined by HAL_ICACHE_SETS.
> 
> The board this was written for was never released publically, but was from 
> TI. I believe this is the CPU: http://www-s.ti.com/sc/ds/omap5910.pdf and 
> more relevantly 
> <http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=OMAP5910&pfsection=user_man>
> which includes the very paragraph you mention!
> 

IIRC, Jesper never got the DATA cache working on that platform
anyway - maybe this is why :-)

> So I'm inclined to believe it's wrong, and a patch is welcome :-).
> 
> > Anyway, I thought I would ask here as well as at TI.  All comments are
> > welcome.
> 
> If you've got the hardware you could play around! At least to verify that 
> it's wrong.
> 

Indeed, and then please share the results!

-- 
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|       Mind: Embedded Linux and eCos Development        |
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| Gary Thomas              email:  gary.thomas@mind.be   |
| Mind ( http://mind.be )  tel:    +1 (970) 229-1963     |
| gpg: http://www.chez-thomas.org/gary/gpg_key.asc       |
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