FROMLIST: pstore-ram: add Device Tree bindings

ramoops is one of the remaining places where ARM vendors still rely on
board-specific shims.  Device Tree lets us replace those shims with
generic code.

These bindings mirror the ramoops module parameters, with two small
differences:

(1) dump_oops becomes an optional "no-dump-oops" property, since ramoops
    sets dump_oops=1 by default.

(2) mem_type=1 becomes the more self-explanatory "unbuffered" property.

(am from https://lkml.org/lkml/2016/1/7/750)

Change-Id: I2140199a861d50fc2bcbbe85b16bf17fb9ccaa1d
Signed-off-by: Greg Hackmann <ghackmann@google.com>

Documentation/devicetree/bindings/misc/ramoops.txt

@@ -0,0 +1,43 @@
+Ramoops oops/panic logger
+=========================
+
+ramoops provides persistent RAM storage for oops and panics, so they can be
+recovered after a reboot.
+
+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.
+
+
+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 no ECC)
+
+- record-size: maximum size in bytes of each dump done on oops/panic
+  (defaults to 0)
+
+- console-size: size in bytes of log buffer reserved for kernel messages
+  (defaults to 0)
+
+- ftrace-size: size in bytes of log buffer reserved for function tracing and
+  profiling (defaults to 0)
+
+- pmsg-size: size in bytes of log buffer reserved for userspace messages
+  (defaults to 0)
+
+- 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)

Documentation/ramoops.txt

@@ -45,7 +45,7 @@ corrupt, but usually it is restorable.
 
 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
@@ -54,7 +54,9 @@ Setting the ramoops parameters can be done in 2 different manners:
  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>

fs/pstore/ram.c

@@ -34,6 +34,8 @@
 #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
@@ -464,15 +466,112 @@ void notrace ramoops_console_write_buf(const char *buf, size_t size)
 	persistent_ram_write(cxt->cprz, buf, size);
 }
 
+static int ramoops_parse_dt_size(struct platform_device *pdev,
+		const char *propname, unsigned long *val)
+{
+	u64 val64;
+	int ret;
+
+	ret = of_property_read_u64(pdev->dev.of_node, propname, &val64);
+	if (ret == -EINVAL) {
+		*val = 0;
+		return 0;
+	} else if (ret != 0) {
+		dev_err(&pdev->dev, "failed to parse property %s: %d\n",
+				propname, ret);
+		return ret;
+	}
+
+	if (val64 > ULONG_MAX) {
+		dev_err(&pdev->dev, "invalid %s %llu\n", propname, val64);
+		return -EOVERFLOW;
+	}
+
+	*val = val64;
+	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 ecc_size;
+	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");
+
+	ret = ramoops_parse_dt_size(pdev, "record-size", &pdata->record_size);
+	if (ret < 0)
+		return ret;
+
+	ret = ramoops_parse_dt_size(pdev, "console-size", &pdata->console_size);
+	if (ret < 0)
+		return ret;
+
+	ret = ramoops_parse_dt_size(pdev, "ftrace-size", &pdata->ftrace_size);
+	if (ret < 0)
+		return ret;
+
+	ret = ramoops_parse_dt_size(pdev, "pmsg-size", &pdata->pmsg_size);
+	if (ret < 0)
+		return ret;
+
+	ret = of_property_read_u32(of_node, "ecc-size", &ecc_size);
+	if (ret == 0) {
+		if (ecc_size > INT_MAX) {
+			dev_err(&pdev->dev, "invalid ecc-size %u\n", ecc_size);
+			return -EOVERFLOW;
+		}
+		pdata->ecc_info.ecc_size = ecc_size;
+	} else if (ret != -EINVAL) {
+		return ret;
+	}
+
+	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 = platform_get_drvdata(pdev);
 	struct ramoops_context *cxt = &oops_cxt;
 	size_t dump_mem_sz;
 	phys_addr_t paddr;
 	int err = -EINVAL;
 
+	if (dev->of_node && !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.
 	 */
@@ -567,6 +666,7 @@ static int ramoops_probe(struct platform_device *pdev)
 		cxt->size, (unsigned long long)cxt->phys_addr,
 		cxt->ecc_info.ecc_size, cxt->ecc_info.block_size);
 
+	platform_set_drvdata(pdev, pdata);
 	return 0;
 
 fail_buf:
@@ -602,11 +702,17 @@ static int ramoops_remove(struct platform_device *pdev)
 	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",
+		.name		= "ramoops",
+		.of_match_table	= dt_match,
 	},
 };