target/linux/ipq40xx/patches-6.6/110-mtd-limit-OTP-nvmem-to-non-nand-devices.patch

   1 From 540dcef6f39d6356d2a65230a8d4e9738ee2d25b Mon Sep 17 00:00:00 2001
   2 From: Christian Marangi <ansuelsmth@gmail.com>
   3 Date: Wed, 20 Mar 2024 16:43:01 +0100
   4 Subject: [PATCH] mtd: limit OTP nvmem to non nand devices
   5
   6 MTD OTP logic is very fragile and can be problematic with some specific
   7 kind of devices.
   8
   9 NVMEM across the years had various iteration on how Cells could be
  10 declared in DT and MTD OTP probably was left behind and
  11 add_legacy_fixed_of_cells was enabled without thinking of the consequences.
  12
  13 That option enables NVMEM to scan the provided of_node and treat each
  14 child as a NVMEM Cell, this was to support legacy NVMEM implementation
  15 and don't cause regression.
  16
  17 This is problematic if we have devices like Nand where the OTP is
  18 triggered by setting a special mode in the flash. In this context real
  19 partitions declared in the Nand node are registered as OTP Cells and
  20 this cause probe fail with -EINVAL error.
  21
  22 This was never notice due to the fact that till now, no Nand supported
  23 the OTP feature. With commit e87161321a40 ("mtd: rawnand: macronix: OTP
  24 access for MX30LFxG18AC") this changed and coincidentally this Nand is
  25 used on an FritzBox 7530 supported on OpenWrt.
  26
  27 Alternative and more robust way to declare OTP Cells are already
  28 prossible by using the fixed-layout node or by declaring a child node
  29 with the compatible set to "otp-user" or "otp-factory".
  30
  31 To fix this and limit any regression with other MTD that makes use of
  32 declaring OTP as direct child of the dev node, disable
  33 add_legacy_fixed_of_cells if we have a node called nand since it's the
  34 standard property name to identify Nand devices attached to a Nand
  35 Controller.
  36
  37 With the following logic, the OTP NVMEM entry is correctly created with
  38 no Cells and the MTD Nand is correctly probed and partitions are
  39 correctly exposed.
  40
  41 Fixes: 2cc3b37f5b6d ("nvmem: add explicit config option to read old syntax fixed OF cells")
  42 Cc: <stable@vger.kernel.org>
  43 Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
  44 ---
  45  drivers/mtd/mtdcore.c | 2 +-
  46  1 file changed, 1 insertion(+), 1 deletion(-)
  47
  48 --- a/drivers/mtd/mtdcore.c
  49 +++ b/drivers/mtd/mtdcore.c
  50 @@ -933,7 +933,7 @@ static struct nvmem_device *mtd_otp_nvme
  51         config.name = compatible;
  52         config.id = NVMEM_DEVID_AUTO;
  53         config.owner = THIS_MODULE;
  54 -       config.add_legacy_fixed_of_cells = true;
  55 +       config.add_legacy_fixed_of_cells = !of_node_name_eq(mtd->dev.of_node, "nand");
  56         config.type = NVMEM_TYPE_OTP;
  57         config.root_only = true;
  58         config.ignore_wp = true;