Since we're going to introduce multiple instances of the CMA heap driver, there's no single CMA heap anymore.

Let's use the heap name instead to differentiate between all the heaps available in the system.

While we're at it, let's also rework the backward compatibility part to make it easier to amend later on.

Reviewed-by: T.J. Mercier tjmercier@google.com Signed-off-by: Maxime Ripard mripard@kernel.org --- Documentation/userspace-api/dma-buf-heaps.rst | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/Documentation/userspace-api/dma-buf-heaps.rst b/Documentation/userspace-api/dma-buf-heaps.rst index 1dfe5e7acd5a3c674323775176d81944147e40c0..17bf6829efd7963bc849765db54d327644e8c395 100644 --- a/Documentation/userspace-api/dma-buf-heaps.rst +++ b/Documentation/userspace-api/dma-buf-heaps.rst @@ -14,15 +14,16 @@ Heaps A heap represents a specific allocator. The Linux kernel currently supports the following heaps:

- The ``system`` heap allocates virtually contiguous, cacheable, buffers.

- - The ``cma`` heap allocates physically contiguous, cacheable, - buffers. Only present if a CMA region is present. Such a region is - usually created either through the kernel commandline through the - ``cma`` parameter, a memory region Device-Tree node with the - ``linux,cma-default`` property set, or through the ``CMA_SIZE_MBYTES`` or - ``CMA_SIZE_PERCENTAGE`` Kconfig options. The heap's name in devtmpfs is - ``default_cma_region``. For backwards compatibility, when the - ``DMABUF_HEAPS_CMA_LEGACY`` Kconfig option is set, a duplicate node is - created following legacy naming conventions; the legacy name might be - ``reserved``, ``linux,cma``, or ``default-pool``. + - The ``default_cma_region`` heap allocates physically contiguous, + cacheable, buffers. Only present if a CMA region is present. Such a + region is usually created either through the kernel commandline + through the ``cma`` parameter, a memory region Device-Tree node with + the ``linux,cma-default`` property set, or through the + ``CMA_SIZE_MBYTES`` or ``CMA_SIZE_PERCENTAGE`` Kconfig options. Prior + to Linux 6.17, its name wasn't stable and could be called + ``reserved``, ``linux,cma``, or ``default-pool``, depending on the + platform. From Linux 6.17 onwards, the creation of these heaps is + controlled through the ``DMABUF_HEAPS_CMA_LEGACY`` Kconfig option for + backwards compatibility.

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.

Reviewed-by: T.J. Mercier tjmercier@google.com Signed-off-by: Maxime Ripard mripard@kernel.org --- kernel/dma/contiguous.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index d9b9dcba6ff7cf5904ac93b72c061fd59072c41b..d67e95094749d45f43c1809c175e491a3f55b2e1 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 @@ -491,9 +492,13 @@ 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

The CMA code, in addition to the reserved-memory regions in the device tree, will also register a default CMA region if the device tree doesn't provide any, with its size and position coming from either the kernel command-line or configuration.

Let's register that one for use to create a heap for it.

Reviewed-by: T.J. Mercier tjmercier@google.com Signed-off-by: Maxime Ripard mripard@kernel.org --- kernel/dma/contiguous.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index d67e95094749d45f43c1809c175e491a3f55b2e1..d8fd6f779f797f711b8e0fd628f868d644b8f784 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -240,17 +240,23 @@ void __init dma_contiguous_reserve(phys_addr_t limit) selected_size = max(size_bytes, cma_early_percent_memory()); #endif }

if (selected_size && !dma_contiguous_default_area) { + int ret; + pr_debug("%s: reserving %ld MiB for global area\n", __func__, (unsigned long)selected_size / SZ_1M);

dma_contiguous_reserve_area(selected_size, selected_base, selected_limit, &dma_contiguous_default_area, fixed); + + ret = dma_heap_cma_register_heap(dma_contiguous_default_area); + if (ret) + pr_warn("Couldn't register default CMA heap."); } }

void __weak dma_contiguous_early_fixup(phys_addr_t base, unsigned long size)

Aside from the main CMA region, it can be useful to allow userspace to allocate from the other CMA reserved regions.

Indeed, those regions can have specific properties that can be useful to a specific us-case.

For example, one of them platform I've been with has ECC enabled on the entire memory but for a specific region. Using that region to allocate framebuffers can be particular beneficial because enabling the ECC has a performance and memory footprint cost.

Thus, exposing these regions as heaps user-space can allocate from and import wherever needed allows to cover that use-case.

For now, only shared-dma-pools regions with the reusable property (ie, backed by CMA) are supported, but eventually we'll want to support other DMA pools types.

Since we collected all the CMA regions created during boot, we can simply iterate over all of them to create the heaps.

This has a weird interaction with the recent work on the CMA name, in particular the backward compatibility code created by commit 854acbe75ff4 ("dma-buf: heaps: Give default CMA heap a fixed name").

Indeed, the old name was either 'reserved', or the name of the reserved-memory region device tree node if the linux,cma-default property was set.

In both these cases, we have now collected this region during boot, and we're using the same name. So we're now largely redundant with the code to handle backward compatibility code, and we can thus remove it and the associated Kconfig option.

Reviewed-by: T.J. Mercier tjmercier@google.com Signed-off-by: Maxime Ripard mripard@kernel.org --- Documentation/userspace-api/dma-buf-heaps.rst | 9 +++++--- drivers/dma-buf/heaps/Kconfig | 10 -------- drivers/dma-buf/heaps/cma_heap.c | 33 +++++++++++++-------------- 3 files changed, 22 insertions(+), 30 deletions(-)

diff --git a/Documentation/userspace-api/dma-buf-heaps.rst b/Documentation/userspace-api/dma-buf-heaps.rst index 17bf6829efd7963bc849765db54d327644e8c395..b78d2faeba62cda721a1f49d49e02bcb520ad429 100644 --- a/Documentation/userspace-api/dma-buf-heaps.rst +++ b/Documentation/userspace-api/dma-buf-heaps.rst @@ -22,8 +22,11 @@ following heaps: through the ``cma`` parameter, a memory region Device-Tree node with the ``linux,cma-default`` property set, or through the ``CMA_SIZE_MBYTES`` or ``CMA_SIZE_PERCENTAGE`` Kconfig options. Prior to Linux 6.17, its name wasn't stable and could be called ``reserved``, ``linux,cma``, or ``default-pool``, depending on the - platform. From Linux 6.17 onwards, the creation of these heaps is - controlled through the ``DMABUF_HEAPS_CMA_LEGACY`` Kconfig option for - backwards compatibility. + platform. + + - A heap will be created for each reusable region in the device tree + with the ``shared-dma-pool`` compatible, using the full device tree + node name as its name. The buffer semantics are identical to + ``default-cma-region``. diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index bb369b38b001af51721b56e065df92825022f1f1..a5eef06c422644e8aadaf5aff2bd9a33c49c1ba3 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -10,15 +10,5 @@ config DMABUF_HEAPS_CMA depends on DMABUF_HEAPS && DMA_CMA help Choose this option to enable dma-buf CMA heap. This heap is backed by the Contiguous Memory Allocator (CMA). If your system has these regions, you should say Y here. - -config DMABUF_HEAPS_CMA_LEGACY - bool "Legacy DMA-BUF CMA Heap" - default y - depends on DMABUF_HEAPS_CMA - help - Add a duplicate CMA-backed dma-buf heap with legacy naming derived - from the CMA area's devicetree node, or "reserved" if the area is not - defined in the devicetree. This uses the same underlying allocator as - CONFIG_DMABUF_HEAPS_CMA. diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index 2a901af635ed76cdb085915c03258c235e302792..42f88193eab9f8f4571064c7b3b8a73bca20fdf4 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -20,10 +20,12 @@ #include <linux/err.h> #include <linux/highmem.h> #include <linux/io.h> #include <linux/mm.h> #include <linux/module.h> +#include <linux/of.h> +#include <linux/of_reserved_mem.h> #include <linux/scatterlist.h> #include <linux/slab.h> #include <linux/vmalloc.h>

#define DEFAULT_CMA_NAME "default_cma_region" @@ -407,35 +409,32 @@ static int __init __add_cma_heap(struct cma *cma, const char *name) }

return 0; }

-static int __init add_default_cma_heap(void) +static int __init add_cma_heaps(void) { struct cma *default_cma = dev_get_cma_area(NULL); - const char *legacy_cma_name; + unsigned int i; int ret;

- if (!default_cma) - return 0; + if (default_cma) { + ret = __add_cma_heap(default_cma, DEFAULT_CMA_NAME); + if (ret) + return ret; + }

- ret = __add_cma_heap(default_cma, DEFAULT_CMA_NAME); - if (ret) - return ret; + for (i = 0; i < dma_areas_num; i++) { + struct cma *cma = dma_areas[i];

- if (IS_ENABLED(CONFIG_DMABUF_HEAPS_CMA_LEGACY)) { - legacy_cma_name = cma_get_name(default_cma); - if (!strcmp(legacy_cma_name, DEFAULT_CMA_NAME)) { - pr_warn("legacy name and default name are the same, skipping legacy heap\n"); - return 0; + ret = __add_cma_heap(cma, cma_get_name(cma)); + if (ret) { + pr_warn("Failed to add CMA heap %s", cma_get_name(cma)); + continue; }

- ret = __add_cma_heap(default_cma, legacy_cma_name); - if (ret) - pr_warn("failed to add legacy heap: %pe\n", - ERR_PTR(ret)); }

return 0; } -module_init(add_default_cma_heap); +module_init(add_cma_heaps); MODULE_DESCRIPTION("DMA-BUF CMA Heap");