Re: Usage of MTD_UADDR_UNNECESSARY broken?

[Erwin Authried <eauth@softsys.co.at>]

Am Fre, den 12.11.2004 schrieb Alexander Hoffmann um 17:17:
> Erwin Authried wrote:
> 
> >Am Fre, den 12.11.2004 schrieb Alexander Hoffmann um 16:15:
> >  
> >
> >>Hi Thayne,
> >>
> >>sorry for the delayed response.
> >>
> >>Thayne Harbaugh wrote:
> >>
> >>    
> >>
> >>>On Mon, 2004-11-08 at 13:55 +0100, Alexander Hoffmann wrote:
> >>> 
> >>>
> >>>      
> >>>
> >>>>Ben Dooks wrote:
> >>>>
> >>>>   
> >>>>
> >>>>        
> >>>>
> >>>>>On Mon, Nov 08, 2004 at 12:54:16PM +0100, Alexander Hoffmann wrote:
> >>>>>     
> >>>>>
> >>>>>          
> >>>>>
> >>>>>>Hi everyone,
> >>>>>>
> >>>>>>can anybody please explain me the exact difference between 
> >>>>>>MTD_UADDR_DONT_CARE and MTD_UADDR_UNNECESSARY .
> >>>>>>Because if I use MTD_UADDR_UNNECESSARY an not existing field in the 
> >>>>>>unlock_addrs array is beeing referenced
> >>>>>>(/drivers/mtd/chips/jedec_probe.c, function cfi_jedec_setup, line 1740):
> >>>>>>
> >>>>>>/* Mask out address bits which are smaller than the device type */
> >>>>>>mask = ~(p_cfi->device_type-1);
> >>>>>>p_cfi->addr_unlock1 = unlock_addrs[uaddr].addr1 & mask;
> >>>>>>p_cfi->addr_unlock2 = unlock_addrs[uaddr].addr2 & mask;
> >>>>>>       
> >>>>>>
> >>>>>>            
> >>>>>>
> >>>>>hmm, thought this masking had been eliminated in later copies of
> >>>>>the mtd code?
> >>>>>     
> >>>>>
> >>>>>          
> >>>>>
> >>>Yes, the masking has been eliminated, but someone left the comment in
> >>>(doh!).
> >>>
> >>> 
> >>>
> >>>      
> >>>
> >>>>Ok, you are right. But this doesn't change the fact that
> >>>>
> >>>>unlock_addrs[uaddr].addr1
> >>>>
> >>>>refers to an nonexisting field in the unlock_addrs array.
> >>>>   
> >>>>
> >>>>        
> >>>>
> >>>I don't see how the code you that you described is being reached.  It
> >>>looks like the start of jedec_probe_chip() checks for UNNECESSARY and
> >>>returns 0 (although I would expect 1) and so cfi_jedec_setup() should
> >>>never be called with UNNECESSARY (even for subsequent chips).
> >>>
> >>>      
> >>>
> >>I am working with the cdb89712 development board from cirrus. This board 
> >>has an "Intel 28F320B3B" chip
> >>(device_id  =  0x8897). Apparently, jedec_probe() finds 
> >>MTD_UADDR_0x0555_0x02AA.
> >>for this chip, while the jedec_table[] specifies it as 
> >>MTD_UADDR_UNNECESSARY.
> >>Since the probed unlock type is overidden by the static one, the code 
> >>_does_ reach
> >>jedec_setup().
> >>
> >>What I haven't really understood is this: if the code refuses chips of  
> >>type UNNECESSARY
> >>(the return code 0 from jedec_probe() is an error), then why are so many 
> >>chips declared
> >>as UNECESSARY in jedec_table[]?
> >>    
> >>
> >
> >MTD_UADDR_UNNECESSARY is used to specify that the chip does not need any
> >unlock sequence at all. The "return 0" statement near the  top of
> >jedec_probe_chip is executed if all possible unlock sequences have been
> >tried without finding a match in jedec table, thus it indicates an
> >error. It's correct that your chip finds a match with
> >MTD_UADDR_0x0555_0x02aa, because that's the first try and the chip
> >doesn't care at all about the unlock sequence. 
> >  
> >
> Does this mean, that the "return 0" statement at the beginning of 
> jedec_probe_chip() is only reached
> when my chip isn't lsited in jedec_table[] ?
> If it is listed , there will always be a match and therefore the 
> functions cfi_jedec_setup() and finfo_uaddr()
> will be called !?
> 
> Alex.
> 

Yes, I think it should work that way. For flash with Intel cmdset,
MTD_UADDR_UNNECESSARY is always used, because they do not use unlocking
at all. In contrast, all AMD cmdset flashchips use unlocking.

Regards,
Erwin