On 18/07/2025 04:34, Adrián Larumbe wrote:
> On 16.05.2025 16:49, Lukas Zapolskas wrote:
>> To allow for combining the requests from multiple userspace clients, an
>> intermediary layer between the HW/FW interfaces and userspace is
>> created, containing the information for the counter requests and
>> tracking of insert and extract indices. Each session starts inactive and
>> must be explicitly activated via PERF_CONTROL.START, and explicitly
>> stopped via PERF_CONTROL.STOP. Userspace identifies a single client with
>> its session ID and the panthor file it is associated with.
>>
>> The SAMPLE and STOP commands both produce a single sample when called,
>> and these samples can be disambiguated via the opaque user data field
>> passed in the PERF_CONTROL uAPI. If this functionality is not desired,
>> these fields can be kept as zero, as the kernel copies this value into
>> the corresponding sample without attempting to interpret it.
>>
>> Currently, only manual sampling sessions are supported, providing
>> samples when userspace calls PERF_CONTROL.SAMPLE, and only a single
>> session is allowed at a time. Multiple sessions and periodic sampling
>> will be enabled in following patches.
>>
>> No protection is provided against the 32-bit hardware counter overflows,
>> so for the moment it is up to userspace to ensure that the counters are
>> sampled at a reasonable frequency.
>>
>> The counter set enum is added to the uapi to clarify the restrictions on
>> calling the interface.
>>
>> Signed-off-by: Lukas Zapolskas <lukas.zapols...@arm.com>
>> ---
>> drivers/gpu/drm/panthor/panthor_device.h | 3 +
>> drivers/gpu/drm/panthor/panthor_drv.c | 1 +
>> drivers/gpu/drm/panthor/panthor_perf.c | 694 ++++++++++++++++++++++-
>> drivers/gpu/drm/panthor/panthor_perf.h | 16 +
>> 4 files changed, 713 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/panthor/panthor_device.h
>> b/drivers/gpu/drm/panthor/panthor_device.h
>> index 818c4d96d448..3fa0882fe81b 100644
>> --- a/drivers/gpu/drm/panthor/panthor_device.h
>> +++ b/drivers/gpu/drm/panthor/panthor_device.h
>> @@ -225,6 +225,9 @@ struct panthor_file {
>> /** @ptdev: Device attached to this file. */
>> struct panthor_device *ptdev;
>>
>> + /** @drm_file: Corresponding drm_file */
>
>> + struct drm_file *drm_file;
>
> I'm sceptical about adding this here, and suspect we don't need it. I
> mentioned why in the
> review for the next patch.
>
I see what you mean. Will try that out, thanks.
>> +
>> /** @vms: VM pool attached to this file. */
>> struct panthor_vm_pool *vms;
>>
>> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c
>> b/drivers/gpu/drm/panthor/panthor_drv.c
>> index 9d2b716cca45..4c1381320859 100644
>> --- a/drivers/gpu/drm/panthor/panthor_drv.c
>> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
>> @@ -1356,6 +1356,7 @@ panthor_open(struct drm_device *ddev, struct drm_file
>> *file)
>> }
>>
>> pfile->ptdev = ptdev;
>> + pfile->drm_file = file;
>>
>> ret = panthor_vm_pool_create(pfile);
>> if (ret)
>> diff --git a/drivers/gpu/drm/panthor/panthor_perf.c
>> b/drivers/gpu/drm/panthor/panthor_perf.c
>> index 9365ce9fed04..15fa533731f3 100644
>> --- a/drivers/gpu/drm/panthor/panthor_perf.c
>> +++ b/drivers/gpu/drm/panthor/panthor_perf.c
>> @@ -2,13 +2,177 @@
>> /* Copyright 2023 Collabora Ltd */
>> /* Copyright 2025 Arm ltd. */
>>
>> -#include <linux/bitops.h>
>> +#include <drm/drm_gem.h>
>> #include <drm/panthor_drm.h>
>> +#include <linux/bitops.h>
>> +#include <linux/circ_buf.h>
>>
>> #include "panthor_device.h"
>> #include "panthor_fw.h"
>> #include "panthor_perf.h"
>>
>> +/**
>> + * PANTHOR_PERF_EM_BITS - Number of bits in a user-facing enable mask. This
>> must correspond
>> + * to the maximum number of counters available for
>> selection on the newest
>> + * Mali GPUs (128 as of the Mali-Gx15).
>> + */
>> +#define PANTHOR_PERF_EM_BITS (BITS_PER_TYPE(u64) * 2)
>> +
>> +enum panthor_perf_session_state {
>> + /** @PANTHOR_PERF_SESSION_ACTIVE: The session is active and can be used
>> for sampling. */
>> + PANTHOR_PERF_SESSION_ACTIVE = 0,
>> +
>> + /**
>> + * @PANTHOR_PERF_SESSION_OVERFLOW: The session encountered an overflow
>> in one of the
>> + * counters during the last sampling
>> period. This flag
>> + * gets propagated as part of samples
>> emitted for this
>> + * session, to ensure the userspace
>> client can gracefully
>> + * handle this data corruption.
>> + */
>> + PANTHOR_PERF_SESSION_OVERFLOW,
>> +
>> + /* Must be last */
>> + PANTHOR_PERF_SESSION_MAX,
>> +};
>> +
>> +struct panthor_perf_enable_masks {
>> + /**
>> + * @mask: Array of bitmasks indicating the counters userspace
>> requested, where
>> + * one bit represents a single counter. Used to build the
>> firmware configuration
>> + * and ensure that userspace clients obtain only the counters
>> they requested.
>> + */
>> + unsigned long
>> mask[DRM_PANTHOR_PERF_BLOCK_MAX][BITS_TO_LONGS(PANTHOR_PERF_EM_BITS)];
>> +};
>> +
>> +struct panthor_perf_counter_block {
>> + struct drm_panthor_perf_block_header header;
>> + u64 counters[];
>> +};
>
> This is a redefinition.
>
>> +/**
>> + * enum session_sample_type - Enum of the types of samples a session can
>> request.
>> + */
>> +enum session_sample_type {
>> + /** @SAMPLE_TYPE_NONE: A sample has not been requested by this session.
>> */
>> + SAMPLE_TYPE_NONE,
>> +
>> + /** @SAMPLE_TYPE_INITIAL: An initial sample has been requested by this
>> session. */
>> + SAMPLE_TYPE_INITIAL,
>> +
>> + /** @SAMPLE_TYPE_REGULAR: A regular sample has been requested by this
>> session. */
>> + SAMPLE_TYPE_REGULAR,
>> +};
>> +
>> +struct panthor_perf_session {
>> + DECLARE_BITMAP(state, PANTHOR_PERF_SESSION_MAX);
>> +
>> + /**
>> + * @pending_sample_request: The type of sample request that is
>> currently pending:
>> + * - when a sample is not requested, the data
>> should be accumulated
>> + * into the next slot of its ring buffer,
>> but the extract index
>> + * should not be updated, and the user-space
>> session must
>> + * not be signaled.
>> + * - when an initial sample is requested, the
>> data must not be
>> + * emitted into the target ring buffer and
>> the userspace client
>> + * must not be notified.
>> + * - when a regular sample is requested, the
>> data must be emitted
>> + * into the target ring buffer, and the
>> userspace client must
>> + * be signalled.
>> + */
>> + enum session_sample_type pending_sample_request;
>> +
>> + /**
>> + * @user_sample_size: The size of a single sample as exposed to
>> userspace. For the sake of
>> + * simplicity, the current implementation exposes
>> the same structure
>> + * as provided by firmware, after annotating the
>> sample and the blocks,
>> + * and zero-extending the counters themselves (to
>> account for in-kernel
>> + * accumulation).
>> + *
>> + * This may also allow further memory-optimizations
>> of compressing the
>> + * sample to provide only requested blocks, if
>> deemed to be worth the
>> + * additional complexity.
>> + */
>> + size_t user_sample_size;
>> +
>> + /**
>> + * @accum_idx: The last insert index indicates whether the current
>> sample
>> + * needs zeroing before accumulation. This is used to
>> disambiguate
>> + * between accumulating into an intermediate slot in
>> the user ring buffer
>> + * and zero-ing the buffer before copying data over.
>> + */
>> + u32 accum_idx;
>> +
>> + /**
>> + * @sample_freq_ns: Period between subsequent sample requests. Zero
>> indicates that
>> + * userspace will be responsible for requesting
>> samples.
>> + */
>> + u64 sample_freq_ns;
>> +
>> + /** @sample_start_ns: Sample request time, obtained from a monotonic
>> raw clock. */
>> + u64 sample_start_ns;
>> +
>> + /**
>> + * @user_data: Opaque handle passed in when starting a session,
>> requesting a sample (for
>> + * manual sampling sessions only) and when stopping a
>> session. This handle
>> + * allows the disambiguation of a sample in the ringbuffer.
>> + */
>> + u64 user_data;
>> +
>> + /**
>> + * @eventfd: Event file descriptor context used to signal userspace of
>> a new sample
>> + * being emitted.
>> + */
>> + struct eventfd_ctx *eventfd;
>> +
>> + /**
>> + * @enabled_counters: This session's requested counters. Note that
>> these cannot change
>> + * for the lifetime of the session.
>> + */
>> + struct panthor_perf_enable_masks *enabled_counters;
>> +
>> + /** @ringbuf_slots: Slots in the user-facing ringbuffer. */
>> + size_t ringbuf_slots;
>> +
>> + /** @ring_buf: BO for the userspace ringbuffer. */
>> + struct drm_gem_object *ring_buf;
>> +
>> + /**
>> + * @control_buf: BO for the insert and extract indices.
>> + */
>> + struct drm_gem_object *control_buf;
>> +
>> + /** @control: The mapped insert and extract indices. */
>> + struct drm_panthor_perf_ringbuf_control *control;
>> +
>> + /** @samples: The mapping of the @ring_buf into the kernel's VA space.
>> */
>> + u8 *samples;
>> +
>> + /**
>> + * @pending: The list node used by the sampler to track the sessions
>> that have not yet
>> + * received a sample.
>> + */
>> + struct list_head pending;
>> +
>> + /**
>> + * @sessions: The list node used by the sampler to track the sessions
>> waiting for a sample.
>> + */
>> + struct list_head sessions;
>> +
>> + /**
>> + * @pfile: The panthor file which was used to create a session, used
>> for the postclose
>> + * handling and to prevent a misconfigured userspace from
>> closing unrelated
>> + * sessions.
>> + */
>> + struct panthor_file *pfile;
>> +
>> + /**
>> + * @ref: Session reference count. The sample delivery to userspace is
>> asynchronous, meaning
>> + * the lifetime of the session must extend at least until the
>> sample is exposed to
>> + * userspace.
>> + */
>> + struct kref ref;
>> +};
>> +
>> struct panthor_perf {
>> /** @next_session: The ID of the next session. */
>> u32 next_session;
>> @@ -72,6 +236,122 @@ static void panthor_perf_info_init(struct
>> panthor_device *ptdev)
>> perf_info->sample_size = session_get_user_sample_size(perf_info);
>> }
>>
>> +static struct panthor_perf_enable_masks *panthor_perf_create_em(struct
>> drm_panthor_perf_cmd_setup
>> + *setup_args)
>> +{
>> + struct panthor_perf_enable_masks *em = kmalloc(sizeof(*em), GFP_KERNEL);
>> + if (IS_ERR_OR_NULL(em))
>> + return em;
>> +
>> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_FW],
>> + setup_args->fw_enable_mask, PANTHOR_PERF_EM_BITS);
>> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_CSHW],
>> + setup_args->cshw_enable_mask, PANTHOR_PERF_EM_BITS);
>> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_TILER],
>> + setup_args->tiler_enable_mask, PANTHOR_PERF_EM_BITS);
>> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_MEMSYS],
>> + setup_args->memsys_enable_mask, PANTHOR_PERF_EM_BITS);
>> + bitmap_from_arr64(em->mask[DRM_PANTHOR_PERF_BLOCK_SHADER],
>> + setup_args->shader_enable_mask, PANTHOR_PERF_EM_BITS);
>> +
>> + return em;
>> +}
>> +
>> +static u64 session_read_extract_idx(struct panthor_perf_session *session)
>> +{
>> + const u64 slots = session->ringbuf_slots;
>> +
>> + /* Userspace will update their own extract index to indicate that a
>> sample is consumed
>> + * from the ringbuffer, and we must ensure we read the latest value.
>> + */
>> + return smp_load_acquire(&session->control->extract_idx) % slots;
>> +}
>> +
>> +static u64 session_read_insert_idx(struct panthor_perf_session *session)
>> +{
>> + const u64 slots = session->ringbuf_slots;
>> +
>> + /*
>> + * Userspace is able to write to the insert index, since it is mapped
>> + * on the same page as the extract index. This should not happen
>> + * in regular operation.
>
> Why would userspace be able to write into the insert index? I guess in a
> ringbuffer setup, UM updates the extract index when it consumes a
> sample, and the kernel increases the insert index when it writes a new
> sample into the user-facing ringbuffer.
>
Currently, the insert index is mapped at a fixed offset from the extract index
on the same
user visible page. Since they're both mapped as read/write, the user could
write to it
and we need to handle that case to ensure there's no overflow.
>> + */
>> + return smp_load_acquire(&session->control->insert_idx) % slots;
>> +}
>> +
>> +static void session_get(struct panthor_perf_session *session)
>> +{
>> + kref_get(&session->ref);
>> +}
>> +
>> +static void session_free(struct kref *ref)
>> +{
>> + struct panthor_perf_session *session = container_of(ref,
>> typeof(*session), ref);
>> +
>> + if (session->samples && session->ring_buf) {
>> + struct iosys_map map = IOSYS_MAP_INIT_VADDR(session->samples);
>> +
>> + drm_gem_vunmap_unlocked(session->ring_buf, &map);
>
> drm_gem_vunmap_unlocked() isn't declared in drm_gem.h when I rebase the
> patch series onto drm-misc. I guess it means either you're basing this patch
> series on a previous WIP branch or else it's misspelt?
>
Looks like I was based on an old commit, the unlocked variants were renamed to
drop the `_unlocked` postfix
in [0]. Will fix these up.
>> + drm_gem_object_put(session->ring_buf);
>> + }
>> +
>> + if (session->control && session->control_buf) {
>> + struct iosys_map map = IOSYS_MAP_INIT_VADDR(session->control);
>> +
>> + drm_gem_vunmap_unlocked(session->control_buf, &map);
>> + drm_gem_object_put(session->control_buf);
>> + }
>> +
>> + eventfd_ctx_put(session->eventfd);
>> +
>> + kfree(session);
>> +}
>> +
>> +static void session_put(struct panthor_perf_session *session)
>> +{
>> + kref_put(&session->ref, session_free);
>> +}
>> +
>> +/**
>> + * session_find - Find a session associated with the given session ID and
>> + * panthor_file.
>> + * @pfile: Panthor file.
>> + * @perf: Panthor perf.
>> + * @sid: Session ID.
>> + *
>> + * The reference count of a valid session is increased to ensure it does
>> not disappear
>> + * in the window between the XA lock being dropped and the internal session
>> functions
>> + * being called.
>> + *
>> + * Return: valid session pointer or an ERR_PTR.
>> + */
>> +static struct panthor_perf_session *session_find(struct panthor_file *pfile,
>> + struct panthor_perf *perf, u32 sid)
>> +{
>> + struct panthor_perf_session *session;
>> +
>> + if (!perf)
>> + return ERR_PTR(-EINVAL);
>> +
>> + xa_lock(&perf->sessions);
>> + session = xa_load(&perf->sessions, sid);
>> +
>> + if (!session || xa_is_err(session)) {
>> + xa_unlock(&perf->sessions);
>> + return ERR_PTR(-EBADF);
>> + }
>> +
>> + if (session->pfile != pfile) {
>> + xa_unlock(&perf->sessions);
>> + return ERR_PTR(-EINVAL);
>> + }
>> +
>> + session_get(session);
>> + xa_unlock(&perf->sessions);
>> +
>> + return session;
>> +}
>> +
>> /**
>> * panthor_perf_init - Initialize the performance counter subsystem.
>> * @ptdev: Panthor device
>> @@ -109,6 +389,412 @@ int panthor_perf_init(struct panthor_device *ptdev)
>> return ret;
>> }
>>
>> +static int session_validate_set(u8 set)
>> +{
>> + if (set > DRM_PANTHOR_PERF_SET_TERTIARY)
>> + return -EINVAL;
>> +
>> + if (set == DRM_PANTHOR_PERF_SET_PRIMARY)
>> + return 0;
>> +
>> + if (set > DRM_PANTHOR_PERF_SET_PRIMARY)
>> + return capable(CAP_PERFMON) ? 0 : -EACCES;
>> +
>> + return -EINVAL;
>> +}
>> +
>> +/**
>> + * panthor_perf_session_setup - Create a user-visible session.
>> + *
>> + * @ptdev: Handle to the panthor device.
>> + * @perf: Handle to the perf control structure.
>> + * @setup_args: Setup arguments passed in via ioctl.
>> + * @pfile: Panthor file associated with the request.
>> + *
>> + * Creates a new session associated with the session ID returned. When
>> initialized, the
>> + * session must explicitly request sampling to start with a successive call
>> to PERF_CONTROL.START.
>> + *
>> + * Return: non-negative session identifier on success or negative error
>> code on failure.
>> + */
>> +int panthor_perf_session_setup(struct panthor_device *ptdev, struct
>> panthor_perf *perf,
>> + struct drm_panthor_perf_cmd_setup *setup_args,
>> + struct panthor_file *pfile)
>> +{
>> + struct panthor_perf_session *session;
>> + struct drm_gem_object *ringbuffer;
>> + struct drm_gem_object *control;
>> + const size_t slots = setup_args->sample_slots;
>> + struct panthor_perf_enable_masks *em;
>> + struct iosys_map rb_map, ctrl_map;
>> + size_t user_sample_size;
>> + int session_id;
>> + int ret;
>> +
>> + ret = session_validate_set(setup_args->block_set);
>> + if (ret) {
>> + drm_err(&ptdev->base, "Did not meet requirements for set %d\n",
>> + setup_args->block_set);
>> + return ret;
>> + }
>> +
>> + session = kzalloc(sizeof(*session), GFP_KERNEL);
>> + if (ZERO_OR_NULL_PTR(session))
>> + return -ENOMEM;
>> +
>> + ringbuffer = drm_gem_object_lookup(pfile->drm_file,
>> setup_args->ringbuf_handle);
>> + if (!ringbuffer) {
>> + drm_err(&ptdev->base, "Could not find handle %d!\n",
>> setup_args->ringbuf_handle);
>> + ret = -EINVAL;
>> + goto cleanup_session;
>> + }
>> +
>> + control = drm_gem_object_lookup(pfile->drm_file,
>> setup_args->control_handle);
>> + if (!control) {
>> + drm_err(&ptdev->base, "Could not find handle %d!\n",
>> setup_args->control_handle);
>> + ret = -EINVAL;
>> + goto cleanup_ringbuf;
>> + }
>> +
>> + user_sample_size = session_get_user_sample_size(&ptdev->perf_info) *
>> slots;
>> +
>> + if (ringbuffer->size != PFN_ALIGN(user_sample_size)) {
>> + drm_err(&ptdev->base, "Incorrect ringbuffer size from
>> userspace: user %zu vs kernel %lu\n",
>> + ringbuffer->size, PFN_ALIGN(user_sample_size));
>> + ret = -ENOMEM;
>> + goto cleanup_control;
>> + }
>> +
>> + ret = drm_gem_vmap_unlocked(ringbuffer, &rb_map);
>
> Same here, drm_gem_vmap_unlocked() isn't declared in any header files.
>
Will get this one too, thanks.
>> + if (ret)
>> + goto cleanup_control;
>> +
>> + ret = drm_gem_vmap_unlocked(control, &ctrl_map);
>> + if (ret)
>> + goto cleanup_ring_map;
>> +
>> + session->eventfd = eventfd_ctx_fdget(setup_args->fd);
>> + if (IS_ERR(session->eventfd)) {
>> + drm_err(&ptdev->base, "Invalid eventfd %d!\n", setup_args->fd);
>> + ret = PTR_ERR_OR_ZERO(session->eventfd) ?: -EINVAL;
>> + goto cleanup_control_map;
>> + }
>> +
>> + em = panthor_perf_create_em(setup_args);
>> + if (IS_ERR_OR_NULL(em)) {
>> + ret = -ENOMEM;
>> + goto cleanup_eventfd;
>> + }
>> +
>> + INIT_LIST_HEAD(&session->sessions);
>> + INIT_LIST_HEAD(&session->pending);
>> +
>> + session->control = ctrl_map.vaddr;
>> + *session->control = (struct drm_panthor_perf_ringbuf_control) { 0 };
>> +
>> + session->samples = rb_map.vaddr;
>> +
>> + /* TODO This will need validation when we support periodic sampling
>> sessions */
>> + if (setup_args->sample_freq_ns) {
>> + ret = -EOPNOTSUPP;
>> + goto cleanup_em;
>> + }
>> +
>> + ret = xa_alloc_cyclic(&perf->sessions, &session_id, session,
>> perf->session_range,
>> + &perf->next_session, GFP_KERNEL);
>> + if (ret < 0) {
>> + drm_err(&ptdev->base, "System session limit exceeded.\n");
>> + ret = -EBUSY;
>> + goto cleanup_em;
>> + }
>> +
>> + kref_init(&session->ref);
>> + session->enabled_counters = em;
>> +
>> + session->sample_freq_ns = setup_args->sample_freq_ns;
>> + session->user_sample_size = user_sample_size;
>> + session->ring_buf = ringbuffer;
>> + session->ringbuf_slots = slots;
>> + session->control_buf = control;
>> + session->pfile = pfile;
>> + session->accum_idx = U32_MAX;
>> +
>> + return session_id;
>> +
>> +cleanup_em:
>> + kfree(em);
>> +
>> +cleanup_eventfd:
>> + eventfd_ctx_put(session->eventfd);
>> +
>> +cleanup_control_map:
>> + drm_gem_vunmap_unlocked(control, &ctrl_map);
>> +
>> +cleanup_ring_map:
>> + drm_gem_vunmap_unlocked(ringbuffer, &rb_map);
>> +
>> +cleanup_control:
>> + drm_gem_object_put(control);
>> +
>> +cleanup_ringbuf:
>> + drm_gem_object_put(ringbuffer);
>> +
>> +cleanup_session:
>> + kfree(session);
>> +
>> + return ret;
>> +}
>> +
>> +static int session_stop(struct panthor_perf *perf, struct
>> panthor_perf_session *session,
>> + u64 user_data)
>> +{
>> + if (!test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
>> + return 0;
>> +
>> + const u64 extract_idx = session_read_extract_idx(session);
>> + const u64 insert_idx = session_read_insert_idx(session);
>> +
>> + /* Must have at least one slot remaining in the ringbuffer to sample. */
>> + if (WARN_ON_ONCE(!CIRC_SPACE_TO_END(insert_idx, extract_idx,
>> session->ringbuf_slots)))
>> + return -EBUSY;
>> +
>> + session->user_data = user_data;
>> +
>> + clear_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state);
>> +
>> + /* TODO Calls to the FW interface will go here in later patches. */
>> + return 0;
>> +}
>> +
>> +static int session_start(struct panthor_perf *perf, struct
>> panthor_perf_session *session,
>> + u64 user_data)
>> +{
>> + if (test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
>> + return 0;
>> +
>> + set_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state);
>> +
>> + /*
>> + * For manual sampling sessions, a start command does not correspond to
>> a sample,
>> + * and so the user data gets discarded.
>> + */
>> + if (session->sample_freq_ns)
>> + session->user_data = user_data;
>> +
>> + /* TODO Calls to the FW interface will go here in later patches. */
>> + return 0;
>> +}
>> +
>> +static int session_sample(struct panthor_perf *perf, struct
>> panthor_perf_session *session,
>> + u64 user_data)
>> +{
>> + if (!test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
>> + return 0;
>> +
>> + const u64 extract_idx = session_read_extract_idx(session);
>> + const u64 insert_idx = session_read_insert_idx(session);
>> +
>> + /* Manual sampling for periodic sessions is forbidden. */
>> + if (session->sample_freq_ns)
>> + return -EINVAL;
>> +
>> + /*
>> + * Must have at least two slots remaining in the ringbuffer to sample:
>> one for
>> + * the current sample, and one for a stop sample, since a stop command
>> should
>> + * always be acknowledged by taking a final sample and stopping the
>> session.
>> + */
>> + if (CIRC_SPACE_TO_END(insert_idx, extract_idx, session->ringbuf_slots)
>> < 2)
>> + return -EBUSY;
>> +
>> + session->sample_start_ns = ktime_get_raw_ns();
>> + session->user_data = user_data;
>> +
>> + return 0;
>> +}
>> +
>> +static int session_destroy(struct panthor_perf *perf, struct
>> panthor_perf_session *session)
>> +{
>> + session_put(session);
>> +
>> + return 0;
>> +}
>> +
>> +static int session_teardown(struct panthor_perf *perf, struct
>> panthor_perf_session *session)
>> +{
>> + if (test_bit(PANTHOR_PERF_SESSION_ACTIVE, session->state))
>> + return -EINVAL;
>> +
>> + if (READ_ONCE(session->pending_sample_request) == SAMPLE_TYPE_NONE)
>> + return -EBUSY;
>> +
>> + return session_destroy(perf, session);
>> +}
>> +
>> +/**
>> + * panthor_perf_session_teardown - Teardown the session associated with the
>> @sid.
>> + * @pfile: Open panthor file.
>> + * @perf: Handle to the perf control structure.
>> + * @sid: Session identifier.
>> + *
>> + * Destroys a stopped session where the last sample has been explicitly
>> consumed
>> + * or discarded. Active sessions will be ignored.
>> + *
>> + * Return: 0 on success, negative error code on failure.
>> + */
>> +int panthor_perf_session_teardown(struct panthor_file *pfile, struct
>> panthor_perf *perf, u32 sid)
>> +{
>> + int err;
>> + struct panthor_perf_session *session;
>> +
>> + xa_lock(&perf->sessions);
>> + session = __xa_store(&perf->sessions, sid, NULL, GFP_KERNEL);
>> +
>> + if (xa_is_err(session)) {
>> + err = xa_err(session);
>> + goto restore;
>> + }
>> +
>> + if (session->pfile != pfile) {
>> + err = -EINVAL;
>> + goto restore;
>> + }
>> +
>> + session_get(session);
>> + xa_unlock(&perf->sessions);
>> +
>> + err = session_teardown(perf, session);
>> +
>> + session_put(session);
>> +
>> + return err;
>> +
>> +restore:
>> + __xa_store(&perf->sessions, sid, session, GFP_KERNEL);
>> + xa_unlock(&perf->sessions);
>> +
>> + return err;
>> +}
>> +
>> +/**
>> + * panthor_perf_session_start - Start sampling on a stopped session.
>> + * @pfile: Open panthor file.
>> + * @perf: Handle to the panthor perf control structure.
>> + * @sid: Session identifier for the desired session.
>> + * @user_data: An opaque value passed in from userspace.
>> + *
>> + * A session counts as stopped when it is created or when it is explicitly
>> stopped after being
>> + * started. Starting an active session is treated as a no-op.
>> + *
>> + * The @user_data parameter will be associated with all subsequent samples
>> for a periodic
>> + * sampling session and will be ignored for manual sampling ones in favor
>> of the user data
>> + * passed in the PERF_CONTROL.SAMPLE ioctl call.
>> + *
>> + * Return: 0 on success, negative error code on failure.
>> + */
>> +int panthor_perf_session_start(struct panthor_file *pfile, struct
>> panthor_perf *perf,
>> + u32 sid, u64 user_data)
>> +{
>> + struct panthor_perf_session *session = session_find(pfile, perf, sid);
>> + int err;
>> +
>> + if (IS_ERR_OR_NULL(session))
>> + return IS_ERR(session) ? PTR_ERR(session) : -EINVAL;
>> +
>> + err = session_start(perf, session, user_data);
>> +
>> + session_put(session);
>> +
>> + return err;
>> +}
>> +
>> +/**
>> + * panthor_perf_session_stop - Stop sampling on an active session.
>> + * @pfile: Open panthor file.
>> + * @perf: Handle to the panthor perf control structure.
>> + * @sid: Session identifier for the desired session.
>> + * @user_data: An opaque value passed in from userspace.
>> + *
>> + * A session counts as active when it has been explicitly started via the
>> PERF_CONTROL.START
>> + * ioctl. Stopping a stopped session is treated as a no-op.
>> + *
>> + * To ensure data is not lost when sampling is stopping, there must always
>> be at least one slot
>> + * available for the final automatic sample, and the stop command will be
>> rejected if there is not.
>> + *
>> + * The @user_data will always be associated with the final sample.
>> + *
>> + * Return: 0 on success, negative error code on failure.
>> + */
>> +int panthor_perf_session_stop(struct panthor_file *pfile, struct
>> panthor_perf *perf,
>> + u32 sid, u64 user_data)
>> +{
>> + struct panthor_perf_session *session = session_find(pfile, perf, sid);
>> + int err;
>> +
>> + if (IS_ERR_OR_NULL(session))
>> + return IS_ERR(session) ? PTR_ERR(session) : -EINVAL;
>> +
>> + err = session_stop(perf, session, user_data);
>> +
>> + session_put(session);
>> +
>> + return err;
>> +}
>> +
>> +/**
>> + * panthor_perf_session_sample - Request a sample on a manual sampling
>> session.
>> + * @pfile: Open panthor file.
>> + * @perf: Handle to the panthor perf control structure.
>> + * @sid: Session identifier for the desired session.
>> + * @user_data: An opaque value passed in from userspace.
>> + *
>> + * Only an active manual sampler is permitted to request samples directly.
>> Failing to meet either
>> + * of these conditions will cause the sampling request to be rejected.
>> Requesting a manual sample
>> + * with a full ringbuffer will see the request being rejected.
>> + *
>> + * The @user_data will always be unambiguously associated one-to-one with
>> the resultant sample.
>> + *
>> + * Return: 0 on success, negative error code on failure.
>> + */
>> +int panthor_perf_session_sample(struct panthor_file *pfile, struct
>> panthor_perf *perf,
>> + u32 sid, u64 user_data)
>> +{
>> + struct panthor_perf_session *session = session_find(pfile, perf, sid);
>> + int err;
>> +
>> + if (IS_ERR_OR_NULL(session))
>> + return IS_ERR(session) ? PTR_ERR(session) : -EINVAL;
>> +
>> + err = session_sample(perf, session, user_data);
>> +
>> + session_put(session);
>> +
>> + return err;
>> +}
>> +
>> +/**
>> + * panthor_perf_session_destroy - Destroy a sampling session associated
>> with the @pfile.
>> + * @perf: Handle to the panthor perf control structure.
>> + * @pfile: The file being closed.
>> + *
>> + * Must be called when the corresponding userspace process is destroyed and
>> cannot close its
>> + * own sessions. As such, we offer no guarantees about data delivery.
>> + */
>> +void panthor_perf_session_destroy(struct panthor_file *pfile, struct
>> panthor_perf *perf)
>> +{
>> + unsigned long sid;
>> + struct panthor_perf_session *session;
>> +
>> + if (!pfile || !perf)
>> + return;
>> +
>> + xa_for_each(&perf->sessions, sid, session)
>> + {
>> + if (session->pfile == pfile) {
>> + session_destroy(perf, session);
>> + xa_erase(&perf->sessions, sid);
>> + }
>> + }
>> +}
>> +
>> /**
>> * panthor_perf_unplug - Terminate the performance counter subsystem.
>> * @ptdev: Panthor device.
>> @@ -124,8 +810,14 @@ void panthor_perf_unplug(struct panthor_device *ptdev)
>> return;
>>
>> if (!xa_empty(&perf->sessions)) {
>> + unsigned long sid;
>> + struct panthor_perf_session *session;
>> +
>> drm_err(&ptdev->base,
>> "Performance counter sessions active when unplugging
>> the driver!");
>> +
>> + xa_for_each(&perf->sessions, sid, session)
>> + session_destroy(perf, session);
>> }
>>
>> xa_destroy(&perf->sessions);
>> diff --git a/drivers/gpu/drm/panthor/panthor_perf.h
>> b/drivers/gpu/drm/panthor/panthor_perf.h
>> index e4805727b9e7..89d61cd1f017 100644
>> --- a/drivers/gpu/drm/panthor/panthor_perf.h
>> +++ b/drivers/gpu/drm/panthor/panthor_perf.h
>> @@ -7,10 +7,26 @@
>>
>> #include <linux/types.h>
>>
>> +struct drm_panthor_perf_cmd_setup;
>> struct panthor_device;
>> +struct panthor_file;
>> +struct panthor_perf;
>>
>> int panthor_perf_init(struct panthor_device *ptdev);
>> void panthor_perf_unplug(struct panthor_device *ptdev);
>>
>> +int panthor_perf_session_setup(struct panthor_device *ptdev, struct
>> panthor_perf *perf,
>> + struct drm_panthor_perf_cmd_setup *setup_args,
>> + struct panthor_file *pfile);
>> +int panthor_perf_session_teardown(struct panthor_file *pfile, struct
>> panthor_perf *perf,
>> + u32 sid);
>> +int panthor_perf_session_start(struct panthor_file *pfile, struct
>> panthor_perf *perf,
>> + u32 sid, u64 user_data);
>> +int panthor_perf_session_stop(struct panthor_file *pfile, struct
>> panthor_perf *perf,
>> + u32 sid, u64 user_data);
>> +int panthor_perf_session_sample(struct panthor_file *pfile, struct
>> panthor_perf *perf,
>> + u32 sid, u64 user_data);
>> +void panthor_perf_session_destroy(struct panthor_file *pfile, struct
>> panthor_perf *perf);
>> +
>> #endif /* __PANTHOR_PERF_H__ */
>>
>> --
>> 2.33.0.dirty
>
>
> Adrian Larumbe
[0]:
https://lore.kernel.org/dri-devel/20250322212608.40511-2-dmitry.osipe...@collabora.com/
