Messages in this thread | | | From | Marek Vasut <> | Subject | Re: [PATCH] Add support for flag status register on Micron chips | Date | Wed, 9 Apr 2014 12:03:24 +0200 |
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On Tuesday, April 08, 2014 at 06:12:49 PM, grmoore@altera.com wrote: > From: Graham Moore <grmoore@altera.com> > > This is a slightly different version of the patch that Insop Song > submitted > (http://marc.info/?i=201403012022.10111.marex%20()%20denx%20!%20de). > > I talked to Insop, and he agreed I should submit this patch as a follow-on > to his. > > This patch uses a flag in the m25p_ids[] array to determine which chips > need to use the FSR (Flag Status Register). > > Rationale for using the FSR: > > The Micron data sheets say we have to do this, at least for the multi-die > 512M and 1G parts (n25q512 and n25q00). In practice, if we don't check > the FSR for program/erase status, and we rely solely on the status > register (SR), then we get corrupted data in the flash.
I talked to Gerhard yesterday and he told me there is something like that on ONFI NAND. I think I now understand why that new register is in-place. Apparently, in the ONFI NAND case, there is a READY and TRUE-READY signal and one of those reflects that _all_ the dies have finished their operation. This is in my opinion seriously misdesigned as it breaks any kind of backward compatibility.
> Micron told us (Altera) that for multi-die chips based on the 65nm 256MB > die, we need to check the SR first, then check the FSR, which is why the > wait_for_fsr_ready function does that. Future chips based on 45 nm 512MB > die will use the FSR only.
Can these SPI flash makers screw the design even more? OT: Why don't we have a single standard for all the SF chips which won't need all these crappy quirks :-(
Best regards, Marek Vasut
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