Commit 620b470b authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Jonathan Corbet
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remoteproc.txt: standardize document format



Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:

- mark document and section titles;
- adjust identation;
- mark literal blocks
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent ce0f95a5
==========================
Remote Processor Framework
==========================
1. Introduction
Introduction
============
Modern SoCs typically have heterogeneous remote processor devices in asymmetric
multiprocessing (AMP) configurations, which may be running different instances
......@@ -26,44 +29,62 @@ remoteproc will add those devices. This makes it possible to reuse the
existing virtio drivers with remote processor backends at a minimal development
cost.
2. User API
User API
========
::
int rproc_boot(struct rproc *rproc)
- Boot a remote processor (i.e. load its firmware, power it on, ...).
If the remote processor is already powered on, this function immediately
returns (successfully).
Returns 0 on success, and an appropriate error value otherwise.
Note: to use this function you should already have a valid rproc
handle. There are several ways to achieve that cleanly (devres, pdata,
the way remoteproc_rpmsg.c does this, or, if this becomes prevalent, we
might also consider using dev_archdata for this).
Boot a remote processor (i.e. load its firmware, power it on, ...).
If the remote processor is already powered on, this function immediately
returns (successfully).
Returns 0 on success, and an appropriate error value otherwise.
Note: to use this function you should already have a valid rproc
handle. There are several ways to achieve that cleanly (devres, pdata,
the way remoteproc_rpmsg.c does this, or, if this becomes prevalent, we
might also consider using dev_archdata for this).
::
void rproc_shutdown(struct rproc *rproc)
- Power off a remote processor (previously booted with rproc_boot()).
In case @rproc is still being used by an additional user(s), then
this function will just decrement the power refcount and exit,
without really powering off the device.
Every call to rproc_boot() must (eventually) be accompanied by a call
to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug.
Notes:
- we're not decrementing the rproc's refcount, only the power refcount.
which means that the @rproc handle stays valid even after
rproc_shutdown() returns, and users can still use it with a subsequent
rproc_boot(), if needed.
Power off a remote processor (previously booted with rproc_boot()).
In case @rproc is still being used by an additional user(s), then
this function will just decrement the power refcount and exit,
without really powering off the device.
Every call to rproc_boot() must (eventually) be accompanied by a call
to rproc_shutdown(). Calling rproc_shutdown() redundantly is a bug.
.. note::
we're not decrementing the rproc's refcount, only the power refcount.
which means that the @rproc handle stays valid even after
rproc_shutdown() returns, and users can still use it with a subsequent
rproc_boot(), if needed.
::
struct rproc *rproc_get_by_phandle(phandle phandle)
- Find an rproc handle using a device tree phandle. Returns the rproc
handle on success, and NULL on failure. This function increments
the remote processor's refcount, so always use rproc_put() to
decrement it back once rproc isn't needed anymore.
3. Typical usage
Find an rproc handle using a device tree phandle. Returns the rproc
handle on success, and NULL on failure. This function increments
the remote processor's refcount, so always use rproc_put() to
decrement it back once rproc isn't needed anymore.
Typical usage
=============
#include <linux/remoteproc.h>
::
/* in case we were given a valid 'rproc' handle */
int dummy_rproc_example(struct rproc *my_rproc)
{
#include <linux/remoteproc.h>
/* in case we were given a valid 'rproc' handle */
int dummy_rproc_example(struct rproc *my_rproc)
{
int ret;
/* let's power on and boot our remote processor */
......@@ -80,84 +101,111 @@ int dummy_rproc_example(struct rproc *my_rproc)
/* let's shut it down now */
rproc_shutdown(my_rproc);
}
}
API for implementors
====================
4. API for implementors
::
struct rproc *rproc_alloc(struct device *dev, const char *name,
const struct rproc_ops *ops,
const char *firmware, int len)
- Allocate a new remote processor handle, but don't register
it yet. Required parameters are the underlying device, the
name of this remote processor, platform-specific ops handlers,
the name of the firmware to boot this rproc with, and the
length of private data needed by the allocating rproc driver (in bytes).
This function should be used by rproc implementations during
initialization of the remote processor.
After creating an rproc handle using this function, and when ready,
implementations should then call rproc_add() to complete
the registration of the remote processor.
On success, the new rproc is returned, and on failure, NULL.
Note: _never_ directly deallocate @rproc, even if it was not registered
yet. Instead, when you need to unroll rproc_alloc(), use rproc_free().
Allocate a new remote processor handle, but don't register
it yet. Required parameters are the underlying device, the
name of this remote processor, platform-specific ops handlers,
the name of the firmware to boot this rproc with, and the
length of private data needed by the allocating rproc driver (in bytes).
This function should be used by rproc implementations during
initialization of the remote processor.
After creating an rproc handle using this function, and when ready,
implementations should then call rproc_add() to complete
the registration of the remote processor.
On success, the new rproc is returned, and on failure, NULL.
.. note::
**never** directly deallocate @rproc, even if it was not registered
yet. Instead, when you need to unroll rproc_alloc(), use rproc_free().
::
void rproc_free(struct rproc *rproc)
- Free an rproc handle that was allocated by rproc_alloc.
This function essentially unrolls rproc_alloc(), by decrementing the
rproc's refcount. It doesn't directly free rproc; that would happen
only if there are no other references to rproc and its refcount now
dropped to zero.
Free an rproc handle that was allocated by rproc_alloc.
This function essentially unrolls rproc_alloc(), by decrementing the
rproc's refcount. It doesn't directly free rproc; that would happen
only if there are no other references to rproc and its refcount now
dropped to zero.
::
int rproc_add(struct rproc *rproc)
- Register @rproc with the remoteproc framework, after it has been
allocated with rproc_alloc().
This is called by the platform-specific rproc implementation, whenever
a new remote processor device is probed.
Returns 0 on success and an appropriate error code otherwise.
Note: this function initiates an asynchronous firmware loading
context, which will look for virtio devices supported by the rproc's
firmware.
If found, those virtio devices will be created and added, so as a result
of registering this remote processor, additional virtio drivers might get
probed.
Register @rproc with the remoteproc framework, after it has been
allocated with rproc_alloc().
This is called by the platform-specific rproc implementation, whenever
a new remote processor device is probed.
Returns 0 on success and an appropriate error code otherwise.
Note: this function initiates an asynchronous firmware loading
context, which will look for virtio devices supported by the rproc's
firmware.
If found, those virtio devices will be created and added, so as a result
of registering this remote processor, additional virtio drivers might get
probed.
::
int rproc_del(struct rproc *rproc)
- Unroll rproc_add().
This function should be called when the platform specific rproc
implementation decides to remove the rproc device. it should
_only_ be called if a previous invocation of rproc_add()
has completed successfully.
After rproc_del() returns, @rproc is still valid, and its
last refcount should be decremented by calling rproc_free().
Unroll rproc_add().
This function should be called when the platform specific rproc
implementation decides to remove the rproc device. it should
_only_ be called if a previous invocation of rproc_add()
has completed successfully.
Returns 0 on success and -EINVAL if @rproc isn't valid.
After rproc_del() returns, @rproc is still valid, and its
last refcount should be decremented by calling rproc_free().
Returns 0 on success and -EINVAL if @rproc isn't valid.
::
void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type)
- Report a crash in a remoteproc
This function must be called every time a crash is detected by the
platform specific rproc implementation. This should not be called from a
non-remoteproc driver. This function can be called from atomic/interrupt
context.
5. Implementation callbacks
Report a crash in a remoteproc
This function must be called every time a crash is detected by the
platform specific rproc implementation. This should not be called from a
non-remoteproc driver. This function can be called from atomic/interrupt
context.
Implementation callbacks
========================
These callbacks should be provided by platform-specific remoteproc
drivers:
/**
* struct rproc_ops - platform-specific device handlers
* @start: power on the device and boot it
* @stop: power off the device
* @kick: kick a virtqueue (virtqueue id given as a parameter)
*/
struct rproc_ops {
drivers::
/**
* struct rproc_ops - platform-specific device handlers
* @start: power on the device and boot it
* @stop: power off the device
* @kick: kick a virtqueue (virtqueue id given as a parameter)
*/
struct rproc_ops {
int (*start)(struct rproc *rproc);
int (*stop)(struct rproc *rproc);
void (*kick)(struct rproc *rproc, int vqid);
};
};
Every remoteproc implementation should at least provide the ->start and ->stop
handlers. If rpmsg/virtio functionality is also desired, then the ->kick handler
......@@ -179,7 +227,8 @@ the exact virtqueue index to look in is optional: it is easy (and not
too expensive) to go through the existing virtqueues and look for new buffers
in the used rings.
6. Binary Firmware Structure
Binary Firmware Structure
=========================
At this point remoteproc only supports ELF32 firmware binaries. However,
it is quite expected that other platforms/devices which we'd want to
......@@ -207,43 +256,43 @@ resource entries that publish the existence of supported features
or configurations by the remote processor, such as trace buffers and
supported virtio devices (and their configurations).
The resource table begins with this header:
/**
* struct resource_table - firmware resource table header
* @ver: version number
* @num: number of resource entries
* @reserved: reserved (must be zero)
* @offset: array of offsets pointing at the various resource entries
*
* The header of the resource table, as expressed by this structure,
* contains a version number (should we need to change this format in the
* future), the number of available resource entries, and their offsets
* in the table.
*/
struct resource_table {
The resource table begins with this header::
/**
* struct resource_table - firmware resource table header
* @ver: version number
* @num: number of resource entries
* @reserved: reserved (must be zero)
* @offset: array of offsets pointing at the various resource entries
*
* The header of the resource table, as expressed by this structure,
* contains a version number (should we need to change this format in the
* future), the number of available resource entries, and their offsets
* in the table.
*/
struct resource_table {
u32 ver;
u32 num;
u32 reserved[2];
u32 offset[0];
} __packed;
} __packed;
Immediately following this header are the resource entries themselves,
each of which begins with the following resource entry header:
/**
* struct fw_rsc_hdr - firmware resource entry header
* @type: resource type
* @data: resource data
*
* Every resource entry begins with a 'struct fw_rsc_hdr' header providing
* its @type. The content of the entry itself will immediately follow
* this header, and it should be parsed according to the resource type.
*/
struct fw_rsc_hdr {
each of which begins with the following resource entry header::
/**
* struct fw_rsc_hdr - firmware resource entry header
* @type: resource type
* @data: resource data
*
* Every resource entry begins with a 'struct fw_rsc_hdr' header providing
* its @type. The content of the entry itself will immediately follow
* this header, and it should be parsed according to the resource type.
*/
struct fw_rsc_hdr {
u32 type;
u8 data[0];
} __packed;
} __packed;
Some resources entries are mere announcements, where the host is informed
of specific remoteproc configuration. Other entries require the host to
......@@ -252,32 +301,32 @@ is expected, where the firmware requests a resource, and once allocated,
the host should provide back its details (e.g. address of an allocated
memory region).
Here are the various resource types that are currently supported:
/**
* enum fw_resource_type - types of resource entries
*
* @RSC_CARVEOUT: request for allocation of a physically contiguous
* memory region.
* @RSC_DEVMEM: request to iommu_map a memory-based peripheral.
* @RSC_TRACE: announces the availability of a trace buffer into which
* the remote processor will be writing logs.
* @RSC_VDEV: declare support for a virtio device, and serve as its
* virtio header.
* @RSC_LAST: just keep this one at the end
*
* Please note that these values are used as indices to the rproc_handle_rsc
* lookup table, so please keep them sane. Moreover, @RSC_LAST is used to
* check the validity of an index before the lookup table is accessed, so
* please update it as needed.
*/
enum fw_resource_type {
Here are the various resource types that are currently supported::
/**
* enum fw_resource_type - types of resource entries
*
* @RSC_CARVEOUT: request for allocation of a physically contiguous
* memory region.
* @RSC_DEVMEM: request to iommu_map a memory-based peripheral.
* @RSC_TRACE: announces the availability of a trace buffer into which
* the remote processor will be writing logs.
* @RSC_VDEV: declare support for a virtio device, and serve as its
* virtio header.
* @RSC_LAST: just keep this one at the end
*
* Please note that these values are used as indices to the rproc_handle_rsc
* lookup table, so please keep them sane. Moreover, @RSC_LAST is used to
* check the validity of an index before the lookup table is accessed, so
* please update it as needed.
*/
enum fw_resource_type {
RSC_CARVEOUT = 0,
RSC_DEVMEM = 1,
RSC_TRACE = 2,
RSC_VDEV = 3,
RSC_LAST = 4,
};
};
For more details regarding a specific resource type, please see its
dedicated structure in include/linux/remoteproc.h.
......@@ -286,7 +335,8 @@ We also expect that platform-specific resource entries will show up
at some point. When that happens, we could easily add a new RSC_PLATFORM
type, and hand those resources to the platform-specific rproc driver to handle.
7. Virtio and remoteproc
Virtio and remoteproc
=====================
The firmware should provide remoteproc information about virtio devices
that it supports, and their configurations: a RSC_VDEV resource entry
......
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