Re: [PATCH v3 2/2] drivers: dma-contiguous: add initialization from device tree

Add device tree support for contiguous memory regions defined in device
tree. Initialization is done in 2 steps. First, the contiguous memory is
reserved, what happens very early when only flattened device tree is
available. Then on device initialization the corresponding cma regions are
assigned to each device structure.

Signed-off-by: Marek Szyprowski <redacted>
Acked-by: Kyungmin Park <redacted>
---
 .../devicetree/bindings/contiguous-memory.txt      |   94 ++++++++++++++
 arch/arm/boot/dts/skeleton.dtsi                    |    7 +-
 drivers/base/dma-contiguous.c                      |  132 ++++++++++++++++++++
 3 files changed, 232 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/contiguous-memory.txt

diff --git a/Documentation/devicetree/bindings/contiguous-memory.txt b/Documentation/devicetree/bindings/contiguous-memory.txt
new file mode 100644
index 0000000..a733df2
--- /dev/null
+++ b/Documentation/devicetree/bindings/contiguous-memory.txt

@@ -0,0 +1,94 @@
+*** Contiguous Memory binding ***
+
+The /chosen/contiguous-memory node provides runtime configuration of
+contiguous memory regions for Linux kernel. Such regions can be created
+for special usage by various device drivers. A good example are
+contiguous memory allocations or memory sharing with other operating
+system(s) on the same hardware board. Those special memory regions might
+depend on the selected board configuration and devices used on the target
+system.
+
+Parameters for each memory region can be encoded into the device tree
+with the following convention:
+
+contiguous-memory {
+
+       (name): region@(base-address) {
+               reg = <(baseaddr) (size)>;
+               (linux,default-contiguous-region);
+               device = <&device_0 &device_1 ...>
+       };
+};

+
+
+*** Example ***
+
+This example defines a memory configuration containing 2 contiguous
+regions for Linux kernel, one default of all device drivers (named
+contig_mem, autoconfigured at boot time, 64MiB) and one dedicated to the
+framebuffer device (named display_mem, placed at 0x78000000, 64MiB). The
+display_mem region is then assigned to fb@12300000, scaller@12500000 and
+codec@12600000 devices for contiguous memory allocation with Linux
+kernel drivers.
+
+The reason for creating a separate region for framebuffer device is to
+match the framebuffer base address to the one configured by bootloader,
+so once Linux kernel drivers starts no glitches on the displayed boot
+logo appears. Scaller and codec drivers should share the memory
+allocations with framebuffer driver.
+
+/ {
+       /* ... */
+
+       chosen {
+               bootargs = /* ... */
+
+               contiguous-memory {
+
+                       /*
+                        * global autoconfigured region
+                        * for contiguous allocations
+                        */
+                       contig_mem: region@0 {
+                               reg = <0x0 0x4000000>;
+                               linux,default-contiguous-region;
+                       };
+
+                       /*
+                        * special region for framebuffer and
+                        * multimedia processing devices
+                        */
+                       display_mem: region@78000000 {
+                               reg = <0x78000000 0x4000000>;
+                               device = <&fb0 &scaller &codec>;
+                       };
+               };
+       };
+
+       /* ... */
+
+       fb0: fb@12300000 {
+               status = "okay";
+       };
+       scaller: scaller@12500000 {
+               status = "okay";
+       };
+       codec: codec@12600000 {
+               status = "okay";
+       };
+};

diff --git a/arch/arm/boot/dts/skeleton.dtsi b/arch/arm/boot/dts/skeleton.dtsi
index b41d241..cadc3b9 100644
--- a/arch/arm/boot/dts/skeleton.dtsi
+++ b/arch/arm/boot/dts/skeleton.dtsi

@@ -7,7 +7,12 @@
 / {
        #address-cells = <1>;
        #size-cells = <1>;
-       chosen { };
+       chosen {
+               contiguous-memory {
+                       #address-cells = <1>;
+                       #size-cells = <1>;
+               };
+       };
        aliases { };
        memory { device_type = "memory"; reg = <0 0>; };
 };

diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
index 01fe743..ce5f5d1 100644
--- a/drivers/base/dma-contiguous.c
+++ b/drivers/base/dma-contiguous.c

@@ -24,6 +24,9 @@

 #include <linux/memblock.h>
 #include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/of_platform.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/page-isolation.h>

@@ -37,6 +40,7 @@ struct cma {
        unsigned long   base_pfn;
        unsigned long   count;
        unsigned long   *bitmap;
+       char            full_name[32];
 };

 static DEFINE_MUTEX(cma_mutex);

@@ -133,6 +137,52 @@ static __init int cma_activate_area(struct cma *cma)
        return 0;
 }

+/*****************************************************************************/
+
+#ifdef CONFIG_OF
+int __init cma_fdt_scan(unsigned long node, const char *uname,
+                               int depth, void *data)
+{
+       static int level;
+       phys_addr_t base, size;
+       unsigned long len;
+       struct cma *cma;
+       __be32 *prop;
+       int ret;
+
+       if (depth == 1 && strcmp(uname, "chosen") == 0) {
+               level = depth;
+               return 0;
+       }
+
+       if (depth == 2 && strcmp(uname, "contiguous-memory") == 0) {
+               level = depth;
+               return 0;
+       }
+
+       if (level != 2 || depth != 3 || strncmp(uname, "region@", 7) != 0)
+               return 0;
+
+       prop = of_get_flat_dt_prop(node, "reg", &len);
+       if (!prop || (len != 2 * sizeof(unsigned long)))
+               return 0;
+
+       base = be32_to_cpu(prop[0]);
+       size = be32_to_cpu(prop[1]);
+
+       pr_info("Found %s, memory base %lx, size %ld MiB\n", uname,
+               (unsigned long)base, (unsigned long)size / SZ_1M);
+
+       ret = dma_contiguous_reserve_area(size, base, 0, &cma);
+       if (ret == 0) {
+               strcpy(cma->full_name, uname);
+               if (of_get_flat_dt_prop(node, "linux,default-contiguous-region", NULL))
+                       dma_contiguous_default_area = cma;
+       }
+       return 0;
+}
+#endif
+
 /**
  * dma_contiguous_reserve() - reserve area(s) for contiguous memory handling
  * @limit: End address of the reserved memory (optional, 0 for any).

@@ -149,6 +199,10 @@ void __init dma_contiguous_reserve(phys_addr_t limit)

        pr_debug("%s(limit %08lx)\n", __func__, (unsigned long)limit);

+#ifdef CONFIG_OF
+       of_scan_flat_dt(cma_fdt_scan, NULL);
+#endif
+
        if (size_cmdline != -1) {
                sel_size = size_cmdline;
        } else {

@@ -265,6 +319,80 @@ int __init dma_contiguous_add_device(struct device *dev, struct cma *cma)
        return 0;
 }

+#ifdef CONFIG_OF
+
+#define MAX_CMA_MAPS   64
+
+static struct cma_map {
+       struct cma *cma;
+       struct device_node *node;
+} cma_maps[MAX_CMA_MAPS];
+static unsigned cma_map_count;
+
+static void cma_assign_device_from_dt(struct device *dev)
+{
+       int i;
+       for (i = 0; i < cma_map_count; i++) {
+               if (cma_maps[i].node == dev->of_node) {
+                       dev_set_cma_area(dev, cma_maps[i].cma);
+                       pr_info("Assigned CMA %s to %s device\n",
+                               cma_maps[i].cma->full_name,
+                               dev_name(dev));
+               }
+       }
+}
+
+static int cma_device_init_notifier_call(struct notifier_block *nb,
+                                        unsigned long event, void *data)
+{
+       struct device *dev = data;
+       if (event == BUS_NOTIFY_ADD_DEVICE && dev->of_node)
+               cma_assign_device_from_dt(dev);
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block cma_dev_init_nb = {
+       .notifier_call = cma_device_init_notifier_call,
+};
+
+void scan_cma_nodes(void)
+{
+       struct device_node *parent = of_find_node_by_path("/chosen/contiguous-memory");
+       struct device_node *child;
+
+       if (!parent)
+               return;
+
+       for_each_child_of_node(parent, child) {
+               struct cma *cma = NULL;
+               int i;
+
+               for (i = 0; i < cma_area_count; i++) {
+                       char *p = strrchr(child->full_name, '/') + 1;
+                       if (strcmp(p, cma_areas[i].full_name) == 0)
+                               cma = &cma_areas[i];
+               }
+               if (!cma)
+                       continue;
+
+               for (i = 0;; i++) {
+                       struct device_node *node;
+                       node = of_parse_phandle(child, "device", i);
+                       if (!node)
+                               break;
+
+                       if (cma_map_count < MAX_CMA_MAPS) {
+                               cma_maps[cma_map_count].cma = cma;
+                               cma_maps[cma_map_count].node = node;
+                               cma_map_count++;
+                       } else {
+                               pr_err("CMA error: too many devices defined\n");
+                       }
+               }
+       }
+}
+#endif
+
 static int __init cma_init_reserved_areas(void)
 {
        int i;

@@ -275,6 +403,10 @@ static int __init cma_init_reserved_areas(void)
                        return ret;
        }

+#ifdef CONFIG_OF
+       scan_cma_nodes();
+       bus_register_notifier(&platform_bus_type, &cma_dev_init_nb);
+#endif
        return 0;
 }
 core_initcall(cma_init_reserved_areas);
--

1.7.9.5