I have a suggestion here.
I recall that CHRP had a reserved node definition which essentially,
since it was not a lot more than a definition of the bare minimum node
that can describe a memory region, acted as a way to carve out
peripheral addresses. In this case, the device_type would be
"reserved" and a property to mark it as for the Linux contiguous
memory allocator would be prudent here. This way nothing new is being
defined except the property. In the case you want default regions and
supplemental regions, give the linux,contiguous-memory-region property
a value. In the case of the reserved node, the name could be "default"
though and CMA could special-case this.
It doesn't even need to be called reserved-memory or be a child node
of it's own, then, but I also guess this would mean duplicating
#address-cells and #size-cells in every node (that said.. isn't there
a case for a 32-bit system having a >32-bit memory map somewhere that
the kernel somehow needs to know about? On PowerPC I've seen 8GB
hooked up to it on CPUs that didn't have 36-bit addressing, and
therefore could not do anything with that amount of memory. But the
DMA controllers in this case were designed around 36-bit addressing
and could easily access the upper 4GB.. it would have come in handy
for a kind of DMA-assisted buffering whereby you wanted to put all
your network or "graphics" stuff in a safe place and copy it in and
out as needed, or even as 4GB of magical swap space driven by a custom
DMA driver)
The naming of nodes is not really "important" in device-tree, in this
case it might make sense in the same way the regulator guys specify
regulators. In any case where the "default" name does not exist, then
the first parsed becomes the default, but this does mean we'd be kind
of restricting the namespace for everyone based on a Linux kernel
behavior..
If you can search for the device_type = "memory" node you can also
search for all nodes matching device_type = "reserved" under the
memory node, with the appropriate property in place to bundle them up
for adding to CMA, and just carve it out. In fact, this would work
without needing to be in the /memory node at all. Hooray for
device_type, long live device_type? :D
-- Matt
On Mon, Aug 19, 2013 at 10:04 AM, Marek Szyprowski
<m.szyprowski@xxxxxxxxxxx> wrote:
> This patch adds device tree support for contiguous and reserved memory
> regions defined in device tree.
>
> Large memory blocks can be reliably reserved only during early boot.
> This must happen before the whole memory management subsystem is
> initialized, because we need to ensure that the given contiguous blocks
> are not yet allocated by kernel. Also it must happen before kernel
> mappings for the whole low memory are created, to ensure that there will
> be no mappings (for reserved blocks) or mapping with special properties
> can be created (for CMA blocks). This all happens before device tree
> structures are unflattened, so we need to get reserved memory layout
> directly from fdt.
>
> Later, those reserved memory regions are assigned to devices on each
> device structure initialization.
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Acked-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
> Acked-by: Tomasz Figa <t.figa@xxxxxxxxxxx>
> ---
> Documentation/devicetree/bindings/memory.txt | 166 ++++++++++++++++++++++++
> drivers/of/Kconfig | 6 +
> drivers/of/Makefile | 1 +
> drivers/of/of_reserved_mem.c | 175 ++++++++++++++++++++++++++
> drivers/of/platform.c | 5 +
> include/linux/of_reserved_mem.h | 14 +++
> 6 files changed, 367 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/memory.txt
> create mode 100644 drivers/of/of_reserved_mem.c
> create mode 100644 include/linux/of_reserved_mem.h
>
> diff --git a/Documentation/devicetree/bindings/memory.txt b/Documentation/devicetree/bindings/memory.txt
> new file mode 100644
> index 0000000..90e96278
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/memory.txt
> @@ -0,0 +1,166 @@
> +*** Memory binding ***
> +
> +The /memory node provides basic information about the address and size
> +of the physical memory. This node is usually filled or updated by the
> +bootloader, depending on the actual memory configuration of the given
> +hardware.
> +
> +The memory layout is described by the following node:
> +
> +/ {
> + #address-cells = <(n)>;
> + #size-cells = <(m)>;
> + memory {
> + device_type = "memory";
> + reg = <(baseaddr1) (size1)
> + (baseaddr2) (size2)
> + ...
> + (baseaddrN) (sizeN)>;
> + };
> + ...
> +};
> +
> +A memory node follows the typical device tree rules for "reg" property:
> +n: number of cells used to store base address value
> +m: number of cells used to store size value
> +baseaddrX: defines a base address of the defined memory bank
> +sizeX: the size of the defined memory bank
> +
> +
> +More than one memory bank can be defined.
> +
> +
> +*** Reserved memory regions ***
> +
> +In /memory/reserved-memory node one can create additional nodes
> +describing particular reserved (excluded from normal use) memory
> +regions. Such memory regions are usually designed for the special usage
> +by various device drivers. A good example are contiguous memory
> +allocations or memory sharing with other operating system on the same
> +hardware board. Those special memory regions might depend on the 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:
> +
> +[(label):] (name) {
> + compatible = "linux,contiguous-memory-region", "reserved-memory-region";
> + reg = <(address) (size)>;
> + (linux,default-contiguous-region);
> +};
> +
> +compatible: "linux,contiguous-memory-region" - enables binding of this
> + region to Contiguous Memory Allocator (special region for
> + contiguous memory allocations, shared with movable system
> + memory, Linux kernel-specific), alternatively if
> + "reserved-memory-region" - compatibility is defined, given
> + region is assigned for exclusive usage for by the respective
> + devices
> +
> +reg: standard property defining the base address and size of
> + the memory region
> +
> +linux,default-contiguous-region: property indicating that the region
> + is the default region for all contiguous memory
> + allocations, Linux specific (optional)
> +
> +It is optional to specify the base address, so if one wants to use
> +autoconfiguration of the base address, '0' can be specified as a base
> +address in the 'reg' property.
> +
> +The /memory/reserved-memory node must contain the same #address-cells
> +and #size-cells value as the root node.
> +
> +
> +*** Device node's properties ***
> +
> +Once regions in the /memory/reserved-memory node have been defined, they
> +can be assigned to device nodes to enable respective device drivers to
> +access them. The following properties are defined:
> +
> +memory-region = <&phandle_to_defined_region>;
> +
> +This property indicates that the device driver should use the memory
> +region pointed by the given phandle.
> +
> +
> +*** Example ***
> +
> +This example defines a memory consisting of 4 memory banks. 3 contiguous
> +regions are defined for Linux kernel, one default of all device drivers
> +(named contig_mem, placed at 0x72000000, 64MiB), one dedicated to the
> +framebuffer device (labelled display_mem, placed at 0x78000000, 8MiB)
> +and one for multimedia processing (labelled multimedia_mem, placed at
> +0x77000000, 64MiB). 'display_mem' region is then assigned to fb@12300000
> +device for DMA memory allocations (Linux kernel drivers will use CMA is
> +available or dma-exclusive usage otherwise). 'multimedia_mem' is
> +assigned to scaler@12500000 and codec@12600000 devices for contiguous
> +memory allocations when CMA driver is enabled.
> +
> +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.
> +
> +/ {
> + #address-cells = <1>;
> + #size-cells = <1>;
> +
> + /* ... */
> +
> + memory {
> + reg = <0x40000000 0x10000000
> + 0x50000000 0x10000000
> + 0x60000000 0x10000000
> + 0x70000000 0x10000000>;
> +
> + reserved-memory {
> + #address-cells = <1>;
> + #size-cells = <1>;
> +
> + /*
> + * global autoconfigured region for contiguous allocations
> + * (used only with Contiguous Memory Allocator)
> + */
> + contig_region@0 {
> + compatible = "linux,contiguous-memory-region";
> + reg = <0x0 0x4000000>;
> + linux,default-contiguous-region;
> + };
> +
> + /*
> + * special region for framebuffer
> + */
> + display_mem: region@78000000 {
> + compatible = "linux,contiguous-memory-region", "reserved-memory-region";
> + reg = <0x78000000 0x800000>;
> + };
> +
> + /*
> + * special region for multimedia processing devices
> + */
> + multimedia_mem: region@77000000 {
> + compatible = "linux,contiguous-memory-region";
> + reg = <0x77000000 0x4000000>;
> + };
> + };
> + };
> +
> + /* ... */
> +
> + fb0: fb@12300000 {
> + status = "okay";
> + memory-region = <&display_mem>;
> + };
> +
> + scaler: scaler@12500000 {
> + status = "okay";
> + memory-region = <&multimedia_mem>;
> + };
> +
> + codec: codec@12600000 {
> + status = "okay";
> + memory-region = <&multimedia_mem>;
> + };
> +};
> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
> index 80e5c13..a83ab43 100644
> --- a/drivers/of/Kconfig
> +++ b/drivers/of/Kconfig
> @@ -80,4 +80,10 @@ config OF_MTD
> depends on MTD
> def_bool y
>
> +config OF_RESERVED_MEM
> + depends on CMA || (HAVE_GENERIC_DMA_COHERENT && HAVE_MEMBLOCK)
> + def_bool y
> + help
> + Initialization code for DMA reserved memory
> +
> endmenu # OF
> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
> index 1f9c0c4..e7e3322 100644
> --- a/drivers/of/Makefile
> +++ b/drivers/of/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_OF_MDIO) += of_mdio.o
> obj-$(CONFIG_OF_PCI) += of_pci.o
> obj-$(CONFIG_OF_PCI_IRQ) += of_pci_irq.o
> obj-$(CONFIG_OF_MTD) += of_mtd.o
> +obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> new file mode 100644
> index 0000000..95563d33
> --- /dev/null
> +++ b/drivers/of/of_reserved_mem.c
> @@ -0,0 +1,175 @@
> +/*
> + * Device tree based initialization code for reserved memory.
> + *
> + * Copyright (c) 2013 Samsung Electronics Co., Ltd.
> + * http://www.samsung.com
> + * Author: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of the
> + * License or (at your optional) any later version of the license.
> + */
> +
> +#include <asm/dma-contiguous.h>
> +
> +#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/sizes.h>
> +#include <linux/mm_types.h>
> +#include <linux/dma-contiguous.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/of_reserved_mem.h>
> +
> +#define MAX_RESERVED_REGIONS 16
> +struct reserved_mem {
> + phys_addr_t base;
> + unsigned long size;
> + struct cma *cma;
> + char name[32];
> +};
> +static struct reserved_mem reserved_mem[MAX_RESERVED_REGIONS];
> +static int reserved_mem_count;
> +
> +static int __init fdt_scan_reserved_mem(unsigned long node, const char *uname,
> + int depth, void *data)
> +{
> + struct reserved_mem *rmem = &reserved_mem[reserved_mem_count];
> + phys_addr_t base, size;
> + int is_cma, is_reserved;
> + unsigned long len;
> + const char *status;
> + __be32 *prop;
> +
> + is_cma = IS_ENABLED(CONFIG_CMA) &&
> + of_flat_dt_is_compatible(node, "linux,contiguous-memory-region");
> + is_reserved = of_flat_dt_is_compatible(node, "reserved-memory-region");
> +
> + if (!is_reserved && !is_cma) {
> + /* ignore node and scan next one */
> + return 0;
> + }
> +
> + status = of_get_flat_dt_prop(node, "status", &len);
> + if (status && strcmp(status, "okay") != 0) {
> + /* ignore disabled node nad scan next one */
> + return 0;
> + }
> +
> + prop = of_get_flat_dt_prop(node, "reg", &len);
> + if (!prop || (len < (dt_root_size_cells + dt_root_addr_cells) *
> + sizeof(__be32))) {
> + pr_err("Reserved mem: node %s, incorrect \"reg\" property\n",
> + uname);
> + /* ignore node and scan next one */
> + return 0;
> + }
> + base = dt_mem_next_cell(dt_root_addr_cells, &prop);
> + size = dt_mem_next_cell(dt_root_size_cells, &prop);
> +
> + if (!size) {
> + /* ignore node and scan next one */
> + return 0;
> + }
> +
> + pr_info("Reserved mem: found %s, memory base %lx, size %ld MiB\n",
> + uname, (unsigned long)base, (unsigned long)size / SZ_1M);
> +
> + if (reserved_mem_count == ARRAY_SIZE(reserved_mem))
> + return -ENOSPC;
> +
> + rmem->base = base;
> + rmem->size = size;
> + strlcpy(rmem->name, uname, sizeof(rmem->name));
> +
> + if (is_cma) {
> + struct cma *cma;
> + if (dma_contiguous_reserve_area(size, base, 0, &cma) == 0) {
> + rmem->cma = cma;
> + reserved_mem_count++;
> + if (of_get_flat_dt_prop(node,
> + "linux,default-contiguous-region",
> + NULL))
> + dma_contiguous_default_area = cma;
> + }
> + } else if (is_reserved) {
> + if (memblock_remove(base, size) == 0)
> + reserved_mem_count++;
> + else
> + pr_err("Failed to reserve memory for %s\n", uname);
> + }
> +
> + return 0;
> +}
> +
> +static struct reserved_mem *get_dma_memory_region(struct device *dev)
> +{
> + struct device_node *node;
> + const char *name;
> + int i;
> +
> + node = of_parse_phandle(dev->of_node, "memory-region", 0);
> + if (!node)
> + return NULL;
> +
> + name = kbasename(node->full_name);
> + for (i = 0; i < reserved_mem_count; i++)
> + if (strcmp(name, reserved_mem[i].name) == 0)
> + return &reserved_mem[i];
> + return NULL;
> +}
> +
> +/**
> + * of_reserved_mem_device_init() - assign reserved memory region to given device
> + *
> + * This function assign memory region pointed by "memory-region" device tree
> + * property to the given device.
> + */
> +void of_reserved_mem_device_init(struct device *dev)
> +{
> + struct reserved_mem *region = get_dma_memory_region(dev);
> + if (!region)
> + return;
> +
> + if (region->cma) {
> + dev_set_cma_area(dev, region->cma);
> + pr_info("Assigned CMA %s to %s device\n", region->name,
> + dev_name(dev));
> + } else {
> + if (dma_declare_coherent_memory(dev, region->base, region->base,
> + region->size, DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE) != 0)
> + pr_info("Declared reserved memory %s to %s device\n",
> + region->name, dev_name(dev));
> + }
> +}
> +
> +/**
> + * of_reserved_mem_device_release() - release reserved memory device structures
> + *
> + * This function releases structures allocated for memory region handling for
> + * the given device.
> + */
> +void of_reserved_mem_device_release(struct device *dev)
> +{
> + struct reserved_mem *region = get_dma_memory_region(dev);
> + if (!region && !region->cma)
> + dma_release_declared_memory(dev);
> +}
> +
> +/**
> + * early_init_dt_scan_reserved_mem() - create reserved memory regions
> + *
> + * This function grabs memory from early allocator for device exclusive use
> + * defined in device tree structures. It should be called by arch specific code
> + * once the early allocator (memblock) has been activated and all other
> + * subsystems have already allocated/reserved memory.
> + */
> +void __init early_init_dt_scan_reserved_mem(void)
> +{
> + of_scan_flat_dt_by_path("/memory/reserved-memory",
> + fdt_scan_reserved_mem, NULL);
> +}
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index e0a6514..1e4e91d 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -21,6 +21,7 @@
> #include <linux/of_device.h>
> #include <linux/of_irq.h>
> #include <linux/of_platform.h>
> +#include <linux/of_reserved_mem.h>
> #include <linux/platform_device.h>
>
> const struct of_device_id of_default_bus_match_table[] = {
> @@ -196,6 +197,7 @@ EXPORT_SYMBOL(of_device_alloc);
> * Returns pointer to created platform device, or NULL if a device was not
> * registered. Unavailable devices will not get registered.
> */
> +
> struct platform_device *of_platform_device_create_pdata(
> struct device_node *np,
> const char *bus_id,
> @@ -218,6 +220,8 @@ struct platform_device *of_platform_device_create_pdata(
> dev->dev.bus = &platform_bus_type;
> dev->dev.platform_data = platform_data;
>
> + of_reserved_mem_device_init(&dev->dev);
> +
> /* We do not fill the DMA ops for platform devices by default.
> * This is currently the responsibility of the platform code
> * to do such, possibly using a device notifier
> @@ -225,6 +229,7 @@ struct platform_device *of_platform_device_create_pdata(
>
> if (of_device_add(dev) != 0) {
> platform_device_put(dev);
> + of_reserved_mem_device_release(&dev->dev);
> return NULL;
> }
>
> diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
> new file mode 100644
> index 0000000..c841282
> --- /dev/null
> +++ b/include/linux/of_reserved_mem.h
> @@ -0,0 +1,14 @@
> +#ifndef __OF_RESERVED_MEM_H
> +#define __OF_RESERVED_MEM_H
> +
> +#ifdef CONFIG_OF_RESERVED_MEM
> +void of_reserved_mem_device_init(struct device *dev);
> +void of_reserved_mem_device_release(struct device *dev);
> +void early_init_dt_scan_reserved_mem(void);
> +#else
> +static inline void of_reserved_mem_device_init(struct device *dev) { }
> +static inline void of_reserved_mem_device_release(struct device *dev) { }
> +static inline void early_init_dt_scan_reserved_mem(void) { }
> +#endif
> +
> +#endif /* __OF_RESERVED_MEM_H */
> --
> 1.7.9.5
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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