On Tue, 11 Apr 2017 15:02:22 +0000 "Bean Huo (beanhuo)" <beanhuo@xxxxxxxxxx> wrote: > Hi, Boris and Thomas > Let me do some explanation. > > >> if (NAND == SLC ) { // on-die ECC only exists in SLC //check device ID > >> byte 4 > >> if ((ID.byte4 & 0x02) == 0x02) {// internal ECC level ==10b > > > >So here the MT29F1G08ABADAWP datasheet says 0x2 <=> 4bit/512bytes ECC. > > > > If the NAND supports on-die ECC, here should be 10b, not matter it is 8bit or 4bit, > You are correct, MT29F1G08ABADAWP is 0x2, its explanation is 4bit/512bytes ECC. > But for the 70s, it is 8bit on-die ECC, but it is still 10b. > So that why here using these two bits to determine if exist on-die ECC. > What's more, for some old products, they don't support on-die ECC, > Sometimes, here is still 01b, so still need following codes to do further > determinations. Okay, then here is the differentiator. Did you check that on SLC NANDs there's no collision on ID[4].bits[1:0]. I've seen NAND vendors changing their ID scheme in incompatible ways (old fields were replaced by new ones with completely different meanings). I'd really like to make sure we're not mis-interpreting READ_ID information, so maybe we should restrict the test on ONFI NANDs if all NANDs supporting on-die ECC are ONFI compliant. We should probably also check that chip->id.len >= 5. > > >> if (ID.byte4 & 0x80) {//on-Die ECC enabled > > > >Did you read my last reply? > >Thomas discovered that ID[4].bit7 is actually reflecting the ECC engine state (1 if > >the engine is enabled, 0 if it's disabled), not whether the NAND supports on-die > >ECC or not, so no this test is not reliable. > > > For the on-die ECC, it is not always default enabled. It depends on requirement from costumers. > If on-die ECC is not enabled, bit7 is 0. It can be switched through "Feature Operations". So this check is not needed, right? BTW, do you have NANDs where the on-die ECC is always enabled, and if this is the case, what happens when you call SET_FEATURE(disable/enable-ECC) on these NANDs? > > >> if (ONFI.byte112 == 4) > >> 60s SLC NAND with on-die ECC > >> else if (ONFI.byte112 == 8) > >> 70s SLC NAND with on-die ECC > > > >This is completely fucked up! Now the ONFI param page says the NAND requires > >8bits/512bytes, while the ID bytes advertised an on-die ECC providing > >4bits/512bytes correctability. > > I think, my previous answers can answer this confusion. Yep. BTW, sorry for being so harsh in my previous reply. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html