linux-kernel - [PATCH v7 3/5] dma: contiguous: Register reusable CMA regions at boot

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Message-Id: <20250721-dma-buf-ecc-heap-v7-3-031836e1a942@kernel.org>
Date: Mon, 21 Jul 2025 13:17:32 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>, 
 Sumit Semwal <sumit.semwal@...aro.org>, 
 Benjamin Gaignard <benjamin.gaignard@...labora.com>, 
 Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>, 
 "T.J. Mercier" <tjmercier@...gle.com>, 
 Christian König <christian.koenig@....com>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Marek Szyprowski <m.szyprowski@...sung.com>, 
 Robin Murphy <robin.murphy@....com>, Jonathan Corbet <corbet@....net>
Cc: Andrew Davis <afd@...com>, Jared Kangas <jkangas@...hat.com>, 
 Mattijs Korpershoek <mkorpershoek@...nel.org>, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
 dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, 
 iommu@...ts.linux.dev, linux-doc@...r.kernel.org, 
 Maxime Ripard <mripard@...nel.org>
Subject: [PATCH v7 3/5] dma: contiguous: Register reusable CMA regions at
 boot

In order to create a CMA dma-buf heap instance for each CMA heap region
in the system, we need to collect all of them during boot.

They are created from two main sources: the reserved-memory regions in
the device tree, and the default CMA region created from the
configuration or command line parameters, if no default region is
provided in the device tree.

Let's collect all the device-tree defined CMA regions flagged as
reusable.

Signed-off-by: Maxime Ripard <mripard@...nel.org>
---
 kernel/dma/contiguous.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 8df0dfaaca18eeb0a20145512ba64425d2e7601e..e81982c0ee8f5c0654731adb611df4bcc4637c7c 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -40,10 +40,11 @@
 #include <asm/page.h>

 #include <linux/memblock.h>
 #include <linux/err.h>
 #include <linux/sizes.h>
+#include <linux/dma-buf/heaps/cma.h>
 #include <linux/dma-map-ops.h>
 #include <linux/cma.h>
 #include <linux/nospec.h>

 #ifdef CONFIG_CMA_SIZE_MBYTES
@@ -490,9 +491,13 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
 	rmem->priv = cma;

 	pr_info("Reserved memory: created CMA memory pool at %pa, size %ld MiB\n",
 		&rmem->base, (unsigned long)rmem->size / SZ_1M);

+	err = dma_heap_cma_register_heap(cma);
+	if (err)
+		pr_warn("Couldn't register CMA heap.");
+
 	return 0;
 }
 RESERVEDMEM_OF_DECLARE(cma, "shared-dma-pool", rmem_cma_setup);
 #endif

-- 
2.50.1