linux-kernel - [PATCH v3 0/4] MTD physmap: Adding reserved RAM support and fixing reserved

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Message-Id: <20260107-mtd-memregion-v3-0-f9fc9107b992@bootlin.com>
Date: Wed, 07 Jan 2026 14:04:51 +0100
From: Gregory CLEMENT <gregory.clement@...tlin.com>
To: Rob Herring <robh@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, 
 Miquel Raynal <miquel.raynal@...tlin.com>, 
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>, 
 Benoît Monin <benoit.monin@...tlin.com>, 
 Théo Lebrun <theo.lebrun@...tlin.com>, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, linux-mtd@...ts.infradead.org, 
 Gregory CLEMENT <gregory.clement@...tlin.com>
Subject: [PATCH v3 0/4] MTD physmap: Adding reserved RAM support and fixing
 reserved_mem limitations

Hello,

While working on adding reserved RAM support to the MTD physmap
driver, I encountered a limitation in the kernel's reserved memory
support: although the Device Tree specification allows multiple reg
entries for a memory-region node, the kernel only processed the first
one. This limitation prevented proper support for reserved RAM regions
in MTD.

This series addresses both issues:

First, the reserved memory support is extended to fully support
multiple reg entries per memory-region node, ensuring compliance with
the Device Tree specification.

Then, with this foundation in place, the series updates the MTD
physmap driver to support reserved RAM regions. The DT bindings are
extended to allow memory-region for RAM access, and the physmap driver
is modified to use these regions.

Gregory

Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
---
Changes in v3:

- Fix the placement of the __free() annotation in patch 4, and also
  address the same issue in the current codebase with patch 1.
- Add MTD properties directly into /reserved-memory nodes, as
  suggested by Rob.
- Rebase on v6.19-rc1
- Link to v2: https://lore.kernel.org/r/20251121-mtd-memregion-v2-0-c5535fdcebe4@bootlin.com

Changes in v2:

- Properly managed cases where register entries used by the memory
  region are out of order, particularly when one or more register
  entries are mixed with memory region entries in an other node.
- Used "memlog" as the node name instead of "sram," which was misleading.
- Link to v1: https://lore.kernel.org/r/20251117-mtd-memregion-v1-0-7b35611c79a6@bootlin.com

---
Gregory CLEMENT (4):
      of: reserved_mem: Fix placement of __free() annotation
      of: reserved_mem: Support multiple 'reg' entries for memory-region
      dt-bindings: mtd: physmap: Allow using memory-region to access memory resources
      mtd: physmap: Add support for RAM reserved memory regions

 .../devicetree/bindings/mtd/mtd-physmap.yaml       |  69 +++++++---
 drivers/mtd/maps/physmap-core.c                    |  73 ++++++++--
 drivers/of/of_reserved_mem.c                       | 150 ++++++++++++++++++---
 drivers/of/platform.c                              |   2 +
 include/linux/of_reserved_mem.h                    |   4 +
 5 files changed, 252 insertions(+), 46 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20251117-mtd-memregion-8830c1dd70ce

Best regards,
-- 
Grégory CLEMENT, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com