pstore/ram: add Device Tree bindings

Ramoops oops/panic logger

=========================

ramoops provides persistent RAM storage for oops and panics, so they can be

recovered after a reboot. It is a backend to pstore, so this node is named

"ramoops" after the backend, rather than "pstore" which is the subsystem.

Parts of this storage may be set aside for other persistent log buffers, such

as kernel log messages, or for optional ECC error-correction data.  The total

size of these optional buffers must fit in the reserved region.

Any remaining space will be used for a circular buffer of oops and panic

records.  These records have a configurable size, with a size of 0 indicating

that they should be disabled.

At least one of "record-size", "console-size", "ftrace-size", or "pmsg-size"

must be set non-zero, but are otherwise optional as listed below.

Required properties:

- compatible: must be "ramoops"

- memory-region: phandle to a region of memory that is preserved between

  reboots

Optional properties:

- ecc-size: enables ECC support and specifies ECC buffer size in bytes

  (defaults to 0: no ECC)

- record-size: maximum size in bytes of each dump done on oops/panic

  (defaults to 0: disabled)

- console-size: size in bytes of log buffer reserved for kernel messages

  (defaults to 0: disabled)

- ftrace-size: size in bytes of log buffer reserved for function tracing and

  profiling (defaults to 0: disabled)

- pmsg-size: size in bytes of log buffer reserved for userspace messages

  (defaults to 0: disabled)

- unbuffered: if present, use unbuffered mappings to map the reserved region

  (defaults to buffered mappings)

- no-dump-oops: if present, only dump panics (defaults to panics and oops)

2. Setting the parameters

Setting the ramoops parameters can be done in 2 different manners:

Setting the ramoops parameters can be done in 3 different manners:

 1. Use the module parameters (which have the names of the variables described

 as before).

 For quick debugging, you can also reserve parts of memory during boot

 kernel to use only the first 128 MB of memory, and place ECC-protected ramoops

 region at 128 MB boundary:

 "mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1"

 2. Use a platform device and set the platform data. The parameters can then

 2. Use Device Tree bindings, as described in

 Documentation/device-tree/bindings/misc/ramoops.txt.

 3. Use a platform device and set the platform data. The parameters can then

 be set through that platform data. An example of doing that is:

#include <linux/pstore_ram.h>

#include <linux/slab.h>

#include <linux/compiler.h>

#include <linux/pstore_ram.h>

#include <linux/of.h>

#include <linux/of_address.h>

#define RAMOOPS_KERNMSG_HDR "===="

#define MIN_MEM_SIZE 4096UL

	return 0;

}

static int ramoops_parse_dt_size(struct platform_device *pdev,

				 const char *propname, u32 *value)

{

	u32 val32 = 0;

	int ret;

	ret = of_property_read_u32(pdev->dev.of_node, propname, &val32);

	if (ret < 0 && ret != -EINVAL) {

		dev_err(&pdev->dev, "failed to parse property %s: %d\n",

			propname, ret);

		return ret;

	}

	if (val32 > INT_MAX) {

		dev_err(&pdev->dev, "%s %u > INT_MAX\n", propname, val32);

		return -EOVERFLOW;

	}

	*value = val32;

	return 0;

}

static int ramoops_parse_dt(struct platform_device *pdev,

			    struct ramoops_platform_data *pdata)

{

	struct device_node *of_node = pdev->dev.of_node;

	struct device_node *mem_region;

	struct resource res;

	u32 value;

	int ret;

	dev_dbg(&pdev->dev, "using Device Tree\n");

	mem_region = of_parse_phandle(of_node, "memory-region", 0);

	if (!mem_region) {

		dev_err(&pdev->dev, "no memory-region phandle\n");

		return -ENODEV;

	}

	ret = of_address_to_resource(mem_region, 0, &res);

	of_node_put(mem_region);

	if (ret) {

		dev_err(&pdev->dev,

			"failed to translate memory-region to resource: %d\n",

			ret);

		return ret;

	}

	pdata->mem_size = resource_size(&res);

	pdata->mem_address = res.start;

	pdata->mem_type = of_property_read_bool(of_node, "unbuffered");

	pdata->dump_oops = !of_property_read_bool(of_node, "no-dump-oops");

#define parse_size(name, field) {					\

		ret = ramoops_parse_dt_size(pdev, name, &value);	\

		if (ret < 0)						\

			return ret;					\

		field = value;						\

	}

	parse_size("record-size", pdata->record_size);

	parse_size("console-size", pdata->console_size);

	parse_size("ftrace-size", pdata->ftrace_size);

	parse_size("pmsg-size", pdata->pmsg_size);

	parse_size("ecc-size", pdata->ecc_info.ecc_size);

#undef parse_size

	return 0;

}

static int ramoops_probe(struct platform_device *pdev)

{

	struct device *dev = &pdev->dev;

	struct ramoops_platform_data *pdata = pdev->dev.platform_data;

	struct ramoops_platform_data *pdata = dev->platform_data;

	struct ramoops_context *cxt = &oops_cxt;

	size_t dump_mem_sz;

	phys_addr_t paddr;

	int err = -EINVAL;

	if (dev_of_node(dev) && !pdata) {

		pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);

		if (!pdata) {

			err = -ENOMEM;

			goto fail_out;

		}

		err = ramoops_parse_dt(pdev, pdata);

		if (err < 0)

			goto fail_out;

	}

	/* Only a single ramoops area allowed at a time, so fail extra

	 * probes.

	 */

	return 0;

}

static const struct of_device_id dt_match[] = {

	{ .compatible = "ramoops" },

	{}

};

static struct platform_driver ramoops_driver = {

	.probe		= ramoops_probe,

	.remove		= ramoops_remove,

	.driver		= {

		.name		= "ramoops",

		.of_match_table	= dt_match,

	},

};