[U-Boot] [PATCH] Fix CFI flash driver for 8-bit bus support

[Aaron Williams]

I believe this is correct.  I have redone the patch as two patches. The first 
patch fixes the 8-bit addressing and has been tested with both 8 and 16-bit 
support with Spansion. The second patch adds a 1us delay after every reset 
call. In my email correspondence with Spansion they said that at least some 
devices require a 500ns delay after the reset command.

-Aaron

On Monday, April 04, 2011 03:14:17 AM Stefan Roese wrote:
> Hi Aaron,
> 
> On Saturday 02 April 2011 09:17:01 Aaron Williams wrote:
> > This patch corrects the addresses used when working with Spansion/AMD
> > FLASH chips. Addressing for 8 and 16 bits is almost identical except in
> > the 16-bit case the LSB of the address is always 0.  The confusion arose
> > because the addresses in the datasheet for 16-bit mode are word
> > addresses but this code assumed it was byte addresses.
> > 
> > I have only been able to test this on our Octeon boards which use either
> > an 8-bit or 16-bit bus.  I have not tested the case where there's an
> > 8-bit part on a 16-bit bus.
> > 
> > This patch also adds some delays as suggested by Spansion.
> > 
> > If a part can be both 8 and 16-bits, it forces it to work in 8-bit mode
> > if an 8-bit bus is detected.
> 
> Thanks.
> 
> Apart from the comments from Albert and Rogan, here some further notes:
> 
> - Please explain why the delay() calls are added. If really needed, please
>   move them into a separate patch, as this seems unrelated to the 8/16
>   bit issue.
> 
> - Please add a short description and rationale to the commit text (and
>   perhaps to cfi_flash.h), why the offsets for the CFI data are now
>   changed (e.g. 0x10 -> 0x20).
> 
> And one further comment below:
> > @@ -1043,6 +1049,8 @@ int flash_erase (flash_info_t * info, int s_first,
> > int s_last) int prot;
> > 
> >  	flash_sect_t sect;
> >  	int st;
> > 
> > +
> > +	debug("%s: erasing sectors %d to %d\n", __func__, s_first, s_last);
> > 
> >  	if (info->flash_id != FLASH_MAN_CFI) {
> >  	
> >  		puts ("Can't erase unknown flash type - aborted\n");
> > 
> > @@ -1082,6 +1090,7 @@ int flash_erase (flash_info_t * info, int s_first,
> > int s_last) break;
> > 
> >  			case CFI_CMDSET_AMD_STANDARD:
> > 
> >  			case CFI_CMDSET_AMD_EXTENDED:
> > +				flash_write_cmd (info, 0, 0, AMD_CMD_RESET);
> 
> Is this correct? A reset command in every flash_erase() call?
> 
> Thanks.
> 
> Cheers,
> Stefan
>