Hi Manivannan, Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> wrote on Tue, 2 Feb 2021 09:46:14 +0530: > Hi, > > On Mon, Feb 01, 2021 at 03:18:24PM +0100, Miquel Raynal wrote: > > Hi Manivannan, > > > > Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> wrote on Sat, > > 30 Jan 2021 09:24:12 +0530: > > > > > The bbt pointer will be unavailable when NAND_SKIP_BBTSCAN option is > > > set for a NAND chip. The intention is to skip scanning for the bad > > > blocks during boot time. > > > > I don't have the same understanding: this flag skips the bad block > > table scan, not the bad block scan. We do want to scan all the devices > > in order to construct a RAM based table. > > > > > However, the MTD core will call > > > _block_isreserved() and _block_isbad() callbacks unconditionally for > > > the rawnand devices due to the callbacks always present while collecting > > > the ecc stats. > > > > > > The _block_isreserved() callback for rawnand will bail out if bbt > > > pointer is not available. But _block_isbad() will continue without > > > checking for it. So this contradicts with the NAND_SKIP_BBTSCAN option > > > since the bad block check will happen anyways (ie., not much difference > > > between scanning for bad blocks and checking each block for bad ones). > > > > > > Hence, do not check for the bad block if bbt pointer is unavailable. > > > > Not checking for bad blocks at all feels insane. I don't really get the > > scope and goal of such change? > > > > The issue I encountered is, on the Telit FN980 device one of the > partition seems to be protected. So trying to read the bad blocks in > that partition makes the device to reboot during boot. o_O Reading a protected block makes the device to reboot? What is the exact device? Can you share the datasheet? Is this behavior expected? Because it seems really broken to me, a read should not trigger *anything* that bad. > There seems to be no flag passed by the parser for this partition. So > the only way I could let the device to boot is to completely skip the > bad block check. We do have a "lock" property which informs the host to first unlock the device, would this help? Is this locking reversible? > AFAIK, MTD core only supports checking for the reserved blocks to be > used for BBM and there is no way to check for a reserved partition like > this. It sounds like a chip specificity/bug, would it make sense to add a specific vendor implementation for that? > I agree that skipping bad block check is not a sane way but I don't know > any other way to handle this problem. > > Thanks, > Mani > Thanks, Miquèl
