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[0/2] Add support for unprotected spare data page

Message ID 20220429211630.7812-1-ansuelsmth@gmail.com
Headers show
Series Add support for unprotected spare data page | expand

Message

Christian Marangi April 29, 2022, 9:16 p.m. UTC 
Some background about this.
On original qsdk ipq8064 based firmware there was a big separation from 
boot partition and user partition. With boot partition we refer to
partition used to init the router (bootloader, spm firmware and other
internal stuff) With user partition we refer to linux partition and data
partition not used to init the router.
When someone had to write to these boot partition a special mode was
needed, to switch the nand driver to this special configuration.

Upstream version of the nandc driver totally dropped this and the result
is that if someone try to read data from these partition a CRC warning
is printed and if someone try to write that (if for example someone
wants to replace the bootloader) result is a broken system as the data
is badly written.

This series comes to fix this.

A user can declare offset and size of these special partition using the
qcom,boot_pages binding.

An initial implementation of this assumed that the boot_pages started
from the start of the nand but we discover that some device have backup
of these special partition and we can have situation where we have this
partition scheme
- APPSBL (require special mode)
- APPSBLENV (doesn't require special mode)
- ART
- APPSBLBK (back of APPSBL require special mode)
- APPSBLENVBK (back of APPSBLENV doesn't require special mode)
With this configuration we need to declare sparse boot page and we can't
assume boot_pages always starts from the start of the nand.

A user can use this form to declare sparse boot pages 
qcom,boot_pages = <0x0 0x0c80000 0x0c80000 0x0500000>;

The driver internally will parse this array, convert it to nand pages
and check internally on every read/write if this special configuration
should used for that page or the normal one.

The reason for all of this is that qcom FOR SOME REASON, disable ECC for
spare data only for these boot partition and we need to reflect this
special configuration to mute these warning and to permit actually
writing to these pages.

Ansuel Smith (2):
  mtd: nand: raw: qcom_nandc: add support for unprotected spare data
    pages
  dt-bindings: mtd: qcom_nandc: document qcom,boot_pages binding

 .../devicetree/bindings/mtd/qcom,nandc.yaml   |  13 ++
 drivers/mtd/nand/raw/qcom_nandc.c             | 148 +++++++++++++++++-
 2 files changed, 156 insertions(+), 5 deletions(-)