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Date: Thu, 3 Mar 2016 14:34:18 -0800
From: Olof Johansson <olof@...om.net>
To: Greg Hackmann <ghackmann@...gle.com>
Cc: "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Jonathan Corbet <corbet@....net>,
Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Kees Cook <keescook@...omium.org>,
Tony Luck <tony.luck@...el.com>,
John Stultz <john.stultz@...aro.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v3] pstore-ram: add Device Tree bindings
Hi,
On Thu, Jan 7, 2016 at 3:40 PM, Greg Hackmann <ghackmann@...gle.com> wrote:
> 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.
>
> Signed-off-by: Greg Hackmann <ghackmann@...gle.com>
> ---
> Changes in V3:
> - documentation fixes
> - look for "no-ram-oops" property as documented
>
> Changes in V2:
> - make DT binding documentation more generic
>
> Documentation/devicetree/bindings/misc/ramoops.txt | 43 ++++++++
> Documentation/ramoops.txt | 6 +-
> fs/pstore/ram.c | 110 ++++++++++++++++++++-
> 3 files changed, 155 insertions(+), 4 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/misc/ramoops.txt
>
> diff --git a/Documentation/devicetree/bindings/misc/ramoops.txt b/Documentation/devicetree/bindings/misc/ramoops.txt
> new file mode 100644
> index 0000000..5a475fa
> --- /dev/null
> +++ b/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)
> diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
> index 5d86756..9264bca 100644
> --- a/Documentation/ramoops.txt
> +++ b/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>
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 319c3a6..0f2912c 100644
> --- a/fs/pstore/ram.c
> +++ b/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
> @@ -458,15 +460,112 @@ static int ramoops_init_prz(struct device *dev, struct ramoops_context *cxt,
> return 0;
> }
>
> +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);
This seems to hardcode the size to 64-bit. It should probably be
controlled by #size-cells instead?
I actually doubt we'll want ramoops larger than 4GB anytime soon, so
it might make more sense to hardcode to 32, if anything.
> + 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;
> + }
Saying why it's invalid will make for happier developers trying to
figure out what's wrong.
> +
> + *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.
> */
> @@ -561,6 +660,7 @@ 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:
> @@ -596,11 +696,17 @@ 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,
> },
> };
>
> --
> 2.6.0.rc2.230.g3dd15c0
>
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