Messages in this thread | | | Date | Wed, 27 Mar 2024 15:26:55 +0100 | From | Rafał Miłecki <> | Subject | Re: [PATCH v3] mtd: limit OTP NVMEM Cell parse to non Nand devices |
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On 2024-03-22 05:09, Christian Marangi wrote: > MTD OTP logic is very fragile and can be problematic with some specific > kind of devices. > > NVMEM across the years had various iteration on how Cells could be > declared in DT and MTD OTP probably was left behind and > add_legacy_fixed_of_cells was enabled without thinking of the > consequences.
Er... thank you?
> That option enables NVMEM to scan the provided of_node and treat each > child as a NVMEM Cell, this was to support legacy NVMEM implementation > and don't cause regression. > > This is problematic if we have devices like Nand where the OTP is > triggered by setting a special mode in the flash. In this context real > partitions declared in the Nand node are registered as OTP Cells and > this cause probe fail with -EINVAL error. > > This was never notice due to the fact that till now, no Nand supported > the OTP feature. With commit e87161321a40 ("mtd: rawnand: macronix: OTP > access for MX30LFxG18AC") this changed and coincidentally this Nand is > used on an FritzBox 7530 supported on OpenWrt.
So as you noticed this problem was *exposed* by adding OTP support for Macronix NAND chips.
> Alternative and more robust way to declare OTP Cells are already > prossible by using the fixed-layout node or by declaring a child node > with the compatible set to "otp-user" or "otp-factory". > > To fix this and limit any regression with other MTD that makes use of > declaring OTP as direct child of the dev node, disable > add_legacy_fixed_of_cells if we detect the MTD type is Nand. > > With the following logic, the OTP NVMEM entry is correctly created with > no Cells and the MTD Nand is correctly probed and partitions are > correctly exposed. > > Fixes: 2cc3b37f5b6d ("nvmem: add explicit config option to read old > syntax fixed OF cells")
It's not that commit however that introduced the problem. Introducing "add_legacy_fixed_of_cells" just added a clean way of enabling parsing of old cells syntax. Even before my commit NVMEM subsystem was looking for NVMEM cells in NAND devices.
I booted kernel 6.6 which has commit e87161321a40 ("mtd: rawnand: macronix: OTP > access for MX30LFxG18AC") but does NOT have commit 2cc3b37f5b6d ("nvmem: add explicit config option to read old syntax fixed OF cells").
Look at this log from Broadcom Northstar (Linux 6.6): [ 0.410107] nand: device found, Manufacturer ID: 0xc2, Chip ID: 0xdc [ 0.416531] nand: Macronix MX30LF4G18AC [ 0.420409] nand: 512 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64 [ 0.428022] iproc_nand 18028000.nand-controller: detected 512MiB total, 128KiB blocks, 2KiB pages, 16B OOB, 8-bit, BCH-8 [ 0.438991] Scanning device for bad blocks [ 0.873598] Bad eraseblock 738 at 0x000005c40000 [ 1.030279] random: crng init done [ 1.854895] Bad eraseblock 2414 at 0x000012dc0000 [ 2.657354] Bad eraseblock 3783 at 0x00001d8e0000 [ 2.662967] Bad eraseblock 3785 at 0x00001d920000 [ 2.848418] nvmem user-otp1: nvmem: invalid reg on /nand-controller@18028000/nand@0 [ 2.856126] iproc_nand 18028000.nand-controller: error -EINVAL: Failed to register OTP NVMEM device
So to summary it up: 1. Problem exists since much earlier and wasn't introduced by 2cc3b37f5b6d 2. Commit 2cc3b37f5b6d just gives you a clean way of solving this issue 3. Problem was exposed by commit e87161321a40 4. We miss fix for v6.6 which doesn't have 2cc3b37f5b6d (it hit v6.7)
> Cc: <stable@vger.kernel.org> > Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
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