[PATCH 20/21] mm/cma: introduce rmem shared-dmb-pool

[Doug Berger]

A 'shared-dmb-pool' reserved-memory device tree node defines a
Designated Movable Block for use by an associated Contiguous
Memory Allocator.

Devices access the CMA region in the same manner as a 'shared-
dma-pool', but the kernel page allocator is free to use the
memory like any other ZONE_MOVABLE memory.

Signed-off-by: Doug Berger <opendmb@xxxxxxxxx>
---
 drivers/of/of_reserved_mem.c |  5 +++++
 kernel/dma/contiguous.c      | 33 ++++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 0eb9e8898d7b..700c0dc0d3b6 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -123,6 +123,11 @@ static int __init __reserved_mem_alloc_size(unsigned long node,
 		   && !nomap) {
 		/* Need adjust the alignment to satisfy the CMA requirement */
 		align = max_t(phys_addr_t, align, CMA_MIN_ALIGNMENT_BYTES);
+	} else if (IS_ENABLED(CONFIG_CMA)
+		   && of_flat_dt_is_compatible(node, "shared-dmb-pool")) {
+		/* Need adjust the alignment to satisfy CMA/DMB requirements */
+		align = max_t(phys_addr_t, align, CMA_MIN_ALIGNMENT_BYTES);
+		align = max_t(phys_addr_t, align, DMB_MIN_ALIGNMENT_BYTES);
 	}
 
 	prop = of_get_flat_dt_prop(node, "alloc-ranges", &len);
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 6ea80ae42622..65dda12752a7 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -50,6 +50,7 @@
 #include <linux/sizes.h>
 #include <linux/dma-map-ops.h>
 #include <linux/cma.h>
+#include <linux/dmb.h>
 
 #ifdef CONFIG_CMA_SIZE_MBYTES
 #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
@@ -397,10 +398,11 @@ static const struct reserved_mem_ops rmem_cma_ops = {
 	.device_release = rmem_cma_device_release,
 };
 
-static int __init rmem_cma_setup(struct reserved_mem *rmem)
+static int __init _rmem_cma_setup(struct reserved_mem *rmem, bool in_dmb)
 {
 	unsigned long node = rmem->fdt_node;
 	bool default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
+	phys_addr_t align = CMA_MIN_ALIGNMENT_BYTES;
 	struct cma *cma;
 	int err;
 
@@ -414,16 +416,25 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
 	    of_get_flat_dt_prop(node, "no-map", NULL))
 		return -EINVAL;
 
-	if (!IS_ALIGNED(rmem->base | rmem->size, CMA_MIN_ALIGNMENT_BYTES)) {
+	if (in_dmb) {
+		if (default_cma) {
+			pr_err("Reserved memory: cma-default cannot be DMB\n");
+			return -EINVAL;
+		}
+		align = max_t(phys_addr_t, align, DMB_MIN_ALIGNMENT_BYTES);
+	}
+	if (!IS_ALIGNED(rmem->base | rmem->size, align)) {
 		pr_err("Reserved memory: incorrect alignment of CMA region\n");
 		return -EINVAL;
 	}
 
-	err = cma_init_reserved_mem(rmem->base, rmem->size, 0, rmem->name, &cma);
+	err = __cma_init_reserved_mem(rmem->base, rmem->size, 0, rmem->name,
+				      &cma, in_dmb);
 	if (err) {
 		pr_err("Reserved memory: unable to setup CMA region\n");
 		return err;
 	}
+
 	/* Architecture specific contiguous memory fixup. */
 	dma_contiguous_early_fixup(rmem->base, rmem->size);
 
@@ -433,10 +444,22 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
 	rmem->ops = &rmem_cma_ops;
 	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);
+	pr_info("Reserved memory: created %s memory pool at %pa, size %ld MiB\n",
+		in_dmb ? "DMB" : "CMA", &rmem->base,
+		(unsigned long)rmem->size / SZ_1M);
 
 	return 0;
 }
+
+static int __init rmem_cma_setup(struct reserved_mem *rmem)
+{
+	return _rmem_cma_setup(rmem, false);
+}
 RESERVEDMEM_OF_DECLARE(cma, "shared-dma-pool", rmem_cma_setup);
+
+static int __init rmem_cma_in_dmb_setup(struct reserved_mem *rmem)
+{
+	return _rmem_cma_setup(rmem, true);
+}
+RESERVEDMEM_OF_DECLARE(cma_in_dmb, "shared-dmb-pool", rmem_cma_in_dmb_setup);
 #endif
-- 
2.25.1