linux-kernel - [PATCH v2 0/2] m68k: coldfire: Add RNG support and const qualifiers for MCF54418

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Message-Id: <20251107-b4-m5441x-add-rng-support-v2-0-f91d685832b9@yoseli.org>
Date: Fri, 07 Nov 2025 11:29:42 +0100
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: Greg Ungerer <gerg@...ux-m68k.org>, 
 Geert Uytterhoeven <geert@...ux-m68k.org>, 
 Olivia Mackall <olivia@...enic.com>, 
 Herbert Xu <herbert@...dor.apana.org.au>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>
Cc: linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org, 
 linux-crypto@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, 
 Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>, 
 Frank Li <Frank.Li@....com>
Subject: [PATCH v2 0/2] m68k: coldfire: Add RNG support and const
 qualifiers for MCF54418

This series adds support for the MCF54418 hardware random number generator
(RNGB) and improves type safety for platform device resources.

The MCF54418 contains an RNGB hardware block compatible with the imx-rngc
driver. This series enables its use by:
- Adding platform device registration for the RNG hardware
- Enabling the clock at platform initialization
- Making the imx-rngc driver compatible with Coldfire's always-on clock
model using devm_clk_get_optional()

Additionally, following Frank Li's suggestion, all static resource array
in arch/m68k/coldfire/device.c are marked const, moving them to read-only
memory and aligning with kernel API expectations.

Testing on DLC Next board shows:
- Hardware RNG throughput: 26 MB/s
- FIPS 140-2 quality: 0.2% failure rate (rng-tools)
- Boot time improvement: CRNG initialization 7 seconds faster

Changes since v1:
- Split const qualifier changes into a separate patch as suggested by
Frank Li
- Mark all resource arrays (including RNG) as const in device.c
- No functional changes to RNG implementation

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
---
Jean-Michel Hautbois (2):
      m68k: coldfire: Mark platform device resource arrays as const
      m68k: coldfire: Add RNG support for MCF54418

 arch/m68k/coldfire/device.c       | 52 ++++++++++++++++++++++++++++++---------
 arch/m68k/coldfire/m5441x.c       |  2 +-
 arch/m68k/include/asm/m5441xsim.h |  9 +++++++
 drivers/char/hw_random/Kconfig    |  3 ++-
 drivers/char/hw_random/imx-rngc.c |  9 ++++++-
 5 files changed, 60 insertions(+), 15 deletions(-)
---
base-commit: 5e5629c7ce42cfa1da9c6aaaa6d7aff0d396c46e
change-id: 20251107-b4-m5441x-add-rng-support-0fdb8d40210a

Best regards,
-- 
Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>