On Wednesday, April 09, 2014 at 08:14:49 PM, Graham Moore wrote: > On Wed, Apr 9, 2014 at 6:09 AM, Gerhard Sittig <g...@denx.de> wrote: > > On Wed, 2014-04-09 at 12:03 +0200, Marek Vasut wrote: > >> On Tuesday, April 08, 2014 at 06:12:49 PM, grmo...@altera.com wrote: > >> > From: Graham Moore <grmo...@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. > > [...] > > >> > 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. > > > > This sounds to me similar to polling the NAND's R/B pin until the > > operation has completed, to then fetch the STATUS byte to > > determine the execution's result. Does this sound plausible? > > For NOR, do you poll for the "busy" condition to deassert, and > > check for success then? > > Sounds plausible to me. We poll the SR until not busy, then poll the > FSR until it's not busy. Success is when FSR busy is deasserted > within the timeout. > > Micron said we have to read the FSR "at least once", so we don't > read it once for every die or anything like that. I ran a quick > test, and for both the 2-die and 4-die parts, the FSR shows not busy > on the first read after SR not busy.
I'd love to know how this FSR-not-busy is exactly related to SR-not-busy, but I guess only Micron can tell :-/ Best regards, Marek Vasut -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
