Pipe CRC Support

This library wraps up the kernel's support for capturing pipe CRCs into a neat and tidy package. For the detailed usage see all the functions which work on igt_pipe_crc_t. This is supported on all platforms and outputs.

Actually using pipe CRCs to write modeset tests is a bit tricky though, so there is no way to directly check a CRC: Both the details of the plane blending, color correction and other hardware and how exactly the CRC is computed at each tap point vary by hardware generation and are not disclosed.

The only way to use igt_crc_t CRCs therefore is to compare CRCs among each another either for equality or difference. Otherwise CRCs must be treated as completely opaque values. Note that not even CRCs from different pipes or tap points on the same platform can be compared. Hence only use igt_assert_crc_equal() to inspect CRC values captured by the same igt_pipe_crc_t object.

Other debugfs interface wrappers

This covers the miscellaneous debugfs interface wrappers:

igt_debugfs_mount ()

const char *
igt_debugfs_mount (void);

This attempts to locate where debugfs is mounted on the filesystem, and if not found, will then try to mount debugfs at /sys/kernel/debug.

igt_debugfs_path ()

char *
igt_debugfs_path (int device,
                  char *path,
                  int pathlen);

This finds the debugfs directory corresponding to device .

igt_debugfs_dir ()

int
igt_debugfs_dir (int device);

This opens the debugfs directory corresponding to device for use with igt_sysfs_get() and related functions.

igt_debugfs_connector_dir ()

int
igt_debugfs_connector_dir (int device,
                           char *conn_name,
                           int mode);

This opens the debugfs directory corresponding to connector on the device for use with igt_sysfs_get() and related functions.

igt_debugfs_open ()

int
igt_debugfs_open (int fd,
                  const char *filename,
                  int mode);

This opens a debugfs file as a Unix file descriptor. The filename should be relative to the drm device's root, i.e. without "drm/$minor".

igt_debugfs_simple_read ()

int
igt_debugfs_simple_read (int dir,
                         const char *filename,
                         char *buf,
                         int size);

This function is similar to __igt_debugfs_read, the difference is that it expects the debugfs directory to be open and it's descriptor passed as the first argument.

igt_debugfs_search ()

bool
igt_debugfs_search (int fd,
                    const char *filename,
                    const char *substring);

Searches each line in filename for the substring specified in substring .

igt_debugfs_read()

#define             igt_debugfs_read(fd, filename, buf)

This is just a convenience wrapper for __igt_debugfs_read. See its documentation.

igt_assert_crc_equal ()

void
igt_assert_crc_equal (const igt_crc_t *a,
                      const igt_crc_t *b);

Compares two CRC values and fails the testcase if they don't match with igt_fail(). Note that due to CRC collisions CRC based testcase can only assert that CRCs match, never that they are different. Otherwise there might be random testcase failures when different screen contents end up with the same CRC by chance.

igt_check_crc_equal ()

bool
igt_check_crc_equal (const igt_crc_t *a,
                     const igt_crc_t *b);

Compares two CRC values and return whether they match.

igt_crc_to_string_extended ()

char *
igt_crc_to_string_extended (igt_crc_t *crc,
                            char delimiter,
                            int crc_size);

This function allocates a string and formats crc into it, depending on delimiter and crc_size . The caller is responsible for freeing the string.

This should only ever be used for diagnostic debug output.

igt_crc_to_string ()

char *
igt_crc_to_string (igt_crc_t *crc);

This function allocates a string and formats crc into it. The caller is responsible for freeing the string.

This should only ever be used for diagnostic debug output.

igt_require_pipe_crc ()

void
igt_require_pipe_crc (int fd);

Convenience helper to check whether pipe CRC capturing is supported by the kernel. Uses igt_skip to automatically skip the test/subtest if this isn't the case.

igt_pipe_crc_new ()

igt_pipe_crc_t *
igt_pipe_crc_new (int fd,
                  enum pipe pipe,
                  enum intel_pipe_crc_source source);

This sets up a new pipe CRC capture object for the given pipe and source in blocking mode.

igt_pipe_crc_new_nonblock ()

igt_pipe_crc_t *
igt_pipe_crc_new_nonblock (int fd,
                           enum pipe pipe,
                           enum intel_pipe_crc_source source);

This sets up a new pipe CRC capture object for the given pipe and source in nonblocking mode.

igt_pipe_crc_free ()

void
igt_pipe_crc_free (igt_pipe_crc_t *pipe_crc);

Frees all resources associated with pipe_crc .

igt_pipe_crc_start ()

void
igt_pipe_crc_start (igt_pipe_crc_t *pipe_crc);

Starts the CRC capture process on pipe_crc .

igt_pipe_crc_stop ()

void
igt_pipe_crc_stop (igt_pipe_crc_t *pipe_crc);

Stops the CRC capture process on pipe_crc .

igt_pipe_crc_get_crcs ()

int
igt_pipe_crc_get_crcs (igt_pipe_crc_t *pipe_crc,
                       int n_crcs,
                       igt_crc_t **out_crcs);

Read up to n_crcs from pipe_crc . This function does not block, and will return early if not enough CRCs can be captured, if pipe_crc has been opened using igt_pipe_crc_new_nonblock(). It will block until n_crcs are retrieved if pipe_crc has been opened using igt_pipe_crc_new(). out_crcs is alloced by this function and must be released with free() by the caller.

Callers must start and stop the capturing themselves by calling igt_pipe_crc_start() and igt_pipe_crc_stop(). For one-shot CRC collecting look at igt_pipe_crc_collect_crc().

igt_pipe_crc_drain ()

void
igt_pipe_crc_drain (igt_pipe_crc_t *pipe_crc);

Discards all currently queued CRC values from pipe_crc . This function does not block, and is useful to flush pipe_crc . Afterwards you can get a fresh CRC with igt_pipe_crc_get_single().

igt_pipe_crc_get_single ()

void
igt_pipe_crc_get_single (igt_pipe_crc_t *pipe_crc,
                         igt_crc_t *out_crc);

Read a single crc from pipe_crc . This function blocks even when nonblocking CRC is requested.

Callers must start and stop the capturing themselves by calling igt_pipe_crc_start() and igt_pipe_crc_stop(). For one-shot CRC collecting look at igt_pipe_crc_collect_crc().

If capturing has been going on for a while and a fresh crc is required, you should use igt_pipe_crc_get_current() instead.

igt_pipe_crc_get_current ()

void
igt_pipe_crc_get_current (int drm_fd,
                          igt_pipe_crc_t *pipe_crc,
                          igt_crc_t *crc);

Same as igt_pipe_crc_get_single(), but will wait until a new CRC can be captured. This is useful for retrieving the current CRC in a more race free way than igt_pipe_crc_drain() + igt_pipe_crc_get_single().

igt_pipe_crc_collect_crc ()

void
igt_pipe_crc_collect_crc (igt_pipe_crc_t *pipe_crc,
                          igt_crc_t *out_crc);

Read a single CRC from pipe_crc . This function blocks until the CRC is retrieved, irrespective of whether pipe_crc has been opened with igt_pipe_crc_new() or igt_pipe_crc_new_nonblock(). out_crc must be allocated by the caller.

This function takes care of the pipe_crc book-keeping, it will start/stop the collection of the CRC.

This function also calls the interactive debug with the "crc" domain, so you can make use of this feature to actually see the screen that is being CRC'd.

For continuous CRC collection look at igt_pipe_crc_start(), igt_pipe_crc_get_crcs() and igt_pipe_crc_stop().

igt_hpd_storm_set_threshold ()

void
igt_hpd_storm_set_threshold (int fd,
                             unsigned int threshold);

Convienence helper to configure the HPD storm detection threshold for i915 through debugfs. Useful for hotplugging tests where HPD storm detection might get in the way and slow things down.

If the system does not support HPD storm detection, this function does nothing.

See: https://01.org/linuxgraphics/gfx-docs/drm/gpu/i915.htmlhotplug

igt_hpd_storm_reset ()

void
igt_hpd_storm_reset (int fd);

Convienence helper to reset HPD storm detection to it's default settings. If hotplug detection was disabled on any ports due to an HPD storm, it will be immediately re-enabled. Always called on exit if the HPD storm detection threshold was modified during any tests.

If the system does not support HPD storm detection, this function does nothing.

See: https://01.org/linuxgraphics/gfx-docs/drm/gpu/i915.htmlhotplug

igt_hpd_storm_detected ()

bool
igt_hpd_storm_detected (int fd);

Checks whether or not i915 has detected an HPD interrupt storm on any of the system's ports.

This function always returns false on systems that do not support HPD storm detection.

See: https://01.org/linuxgraphics/gfx-docs/drm/gpu/i915.htmlhotplug

igt_require_hpd_storm_ctl ()

void
igt_require_hpd_storm_ctl (int fd);

Skips the current test if the system does not have HPD storm detection.

See: https://01.org/linuxgraphics/gfx-docs/drm/gpu/i915.htmlhotplug

igt_drop_caches_has ()

bool
igt_drop_caches_has (int fd,
                     uint64_t val);

This queries the debugfs to see if it supports the full set of desired operations.

igt_drop_caches_set ()

void
igt_drop_caches_set (int fd,
                     uint64_t val);

This calls the debugfs interface the drm/i915 GEM driver exposes to drop or evict certain classes of gem buffer objects.

igt_disable_prefault ()

void
igt_disable_prefault (void);

Disable prefaulting in certain gem ioctls through the debugfs interface. As usual this installs an exit handler to clean up and re-enable prefaulting even when the test exited abnormally.

igt_enable_prefault() will enable normale operation again.

igt_enable_prefault ()

void
igt_enable_prefault (void);

Enable prefault (again) through the debugfs interface.

igt_get_stable_obj_count ()

int
igt_get_stable_obj_count (int driver);

This puts the driver into a stable (quiescent) state and then returns the current number of gem buffer objects as reported in the i915_gem_objects debugFS interface.

igt_debugfs_dump ()

void
igt_debugfs_dump (int device,
                  const char *filename);

igt_pipe_crc_t

typedef struct _igt_pipe_crc igt_pipe_crc_t;

Pipe CRC support structure. Needs to be allocated and set up with igt_pipe_crc_new() for a specific pipe and pipe CRC source value.

DRM_MAX_CRC_NR

#define DRM_MAX_CRC_NR 10

igt_crc_t

typedef struct {
	uint32_t frame;
	bool has_valid_frame;
	int n_words;
	uint32_t crc[DRM_MAX_CRC_NR];
} igt_crc_t;

Pipe CRC value. All other members than frame are private and should not be inspected by testcases.

enum intel_pipe_crc_source

Enumeration of all supported pipe CRC sources. Not all platforms and all outputs support all of them. Generic tests should just use INTEL_PIPE_CRC_SOURCE_AUTO. It should always map to an end-of-pipe CRC suitable for checking planes, cursor, color correction and any other output-agnostic features.

DROP_UNBOUND

#define DROP_UNBOUND 0x1

Drop all currently unbound gem buffer objects from the cache.

DROP_BOUND

#define DROP_BOUND 0x2

Drop all inactive objects which are bound into some gpu address space.

DROP_RETIRE

#define DROP_RETIRE 0x4

Wait for all outstanding gpu commands to complete, but do not take any further actions.

DROP_ACTIVE

#define DROP_ACTIVE 0x8

Also drop active objects once retired.

DROP_FREED

#define DROP_FREED 0x10

Also drop freed objects.

DROP_SHRINK_ALL

#define DROP_SHRINK_ALL 0x20

Force all unpinned buffers to be evicted from their GTT and returned to the system.

DROP_IDLE

#define DROP_IDLE 0x40

Flush the driver's idle_worker, releasing internal caches and wakerefs.

DROP_RESET_ACTIVE

#define DROP_RESET_ACTIVE 0x80

Cancel all outstanding requests by forcing a gpu reset

DROP_RESET_SEQNO

#define DROP_RESET_SEQNO 0x100

Reset the global request seqno counter back to 0

DROP_ALL

#define             DROP_ALL

All of the above DROP_ flags combined.