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From: Maxime Ripard <mripard@kernel.org>
Subject: [PATCH 0/8] dma-buf: heaps: Support carved-out heaps and ECC
 related-flags
Date: Wed, 15 May 2024 15:56:55 +0200
Message-Id: <20240515-dma-buf-ecc-heap-v1-0-54cbbd049511@kernel.org>
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To: Rob Herring <robh@kernel.org>, Saravana Kannan <saravanak@google.com>, 
 Sumit Semwal <sumit.semwal@linaro.org>, 
 Benjamin Gaignard <benjamin.gaignard@collabora.com>, 
 Brian Starkey <Brian.Starkey@arm.com>, John Stultz <jstultz@google.com>, 
 "T.J. Mercier" <tjmercier@google.com>, 
 =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
Cc: Mattijs Korpershoek <mkorpershoek@baylibre.com>, 
 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, 
 linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, 
 linaro-mm-sig@lists.linaro.org, Maxime Ripard <mripard@kernel.org>

Hi,

This series is the follow-up of the discussion that John and I had a few
months ago here:

https://lore.kernel.org/all/CANDhNCquJn6bH3KxKf65BWiTYLVqSd9892-xtFDHHqqyrroCMQ@mail.gmail.com/

The initial problem we were discussing was that I'm currently working on
a platform which has a memory layout with ECC enabled. However, enabling
the ECC has a number of drawbacks on that platform: lower performance,
increased memory usage, etc. So for things like framebuffers, the
trade-off isn't great and thus there's a memory region with ECC disabled
to allocate from for such use cases.

After a suggestion from John, I chose to start using heap allocations
flags to allow for userspace to ask for a particular ECC setup. This is
then backed by a new heap type that runs from reserved memory chunks
flagged as such, and the existing DT properties to specify the ECC
properties.

We could also easily extend this mechanism to support more flags, or
through a new ioctl to discover which flags a given heap supports.

I submitted a draft PR to the DT schema for the bindings used in this
PR:
https://github.com/devicetree-org/dt-schema/pull/138

Let me know what you think,
Maxime

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
Maxime Ripard (8):
      dma-buf: heaps: Introduce a new heap for reserved memory
      of: Add helper to retrieve ECC memory bits
      dma-buf: heaps: Import uAPI header
      dma-buf: heaps: Add ECC protection flags
      dma-buf: heaps: system: Remove global variable
      dma-buf: heaps: system: Handle ECC flags
      dma-buf: heaps: cma: Handle ECC flags
      dma-buf: heaps: carveout: Handle ECC flags

 drivers/dma-buf/dma-heap.c            |   4 +
 drivers/dma-buf/heaps/Kconfig         |   8 +
 drivers/dma-buf/heaps/Makefile        |   1 +
 drivers/dma-buf/heaps/carveout_heap.c | 330 ++++++++++++++++++++++++++++++++++
 drivers/dma-buf/heaps/cma_heap.c      |  10 ++
 drivers/dma-buf/heaps/system_heap.c   |  29 ++-
 include/linux/dma-heap.h              |   2 +
 include/linux/of.h                    |  25 +++
 include/uapi/linux/dma-heap.h         |   5 +-
 9 files changed, 407 insertions(+), 7 deletions(-)
---
base-commit: a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6
change-id: 20240515-dma-buf-ecc-heap-28a311d2c94e

Best regards,
-- 
Maxime Ripard <mripard@kernel.org>