On 12/5/18 4:01 PM, Kazlauskas, Nicholas wrote: > On 2018-12-05 3:44 p.m., Grodzovsky, Andrey wrote: >> >> >> On 12/05/2018 03:42 PM, Kazlauskas, Nicholas wrote: >>> On 2018-12-05 3:26 p.m., Grodzovsky, Andrey wrote: >>>> >>>> On 12/05/2018 02:59 PM, Nicholas Kazlauskas wrote: >>>>> [Why] >>>>> Legacy cursor plane updates from drm helpers go through the full >>>>> atomic codepath. A high volume of cursor updates through this slow >>>>> code path can cause subsequent page-flips to skip vblank intervals >>>>> since each individual update is slow. >>>>> >>>>> This problem is particularly noticeable for the compton compositor. >>>>> >>>>> [How] >>>>> A fast path for cursor plane updates is added by using DRM asynchronous >>>>> commit support provided by async_check and async_update. These don't do >>>>> a full state/flip_done dependency stall and they don't block other >>>>> commit work. >>>>> >>>>> However, DC still expects itself to be single-threaded for anything >>>>> that can issue register writes. Screen corruption or hangs can occur >>>>> if write sequences overlap. Every call that potentially perform >>>>> register writes needs to be guarded for asynchronous updates to work. >>>>> The dc_lock mutex was added for this. >>>> As far as page flip related register writes concerned this I think this >>>> was never an issue - we always >>>> supported fully concurrent page flips on different CRTCs meaning writing >>>> surface address concurrently >>>> on different pipes. So Are you sure you can't do cursor update >>>> concurrently against at least page flips ? >>>> I am not sure about full updates. >>>> >>>> Andrey >>> I think this was true before we started locking the pipes around cursor >>> updates (and probably only for dce). The problem that occur here is >>> writing to the lock register from multiple threads at the same time. >>> >>> In general I think the "contract" between dm/dc now is that anything >>> from dc that does register write sequences can't be called from multiple >>> threads. >>> >>> Nicholas Kazlauskas >> >> Ok, do note that you also serialize all the page flips now which looks >> unneeded - maybe consider r/w lock to at least avoid that. >> >> Andrey > > Yeah, they definitely shouldn't be happening at the same time as the > cursor calls. > > I'd need to look into whether it's okay now to do concurrent writes from > the stream update functions though, but I'd imagine it's not something > we'd want to be doing. A r/w lock would work if we could though. > > Nicholas Kazlauskas
A reader/writer lock wouldn't help here, actually. Fast updates (and page flips in particular) need to lock the pipe as well, see: commit_planes_for_stream. Nicholas Kazlauskas > >> >>> >>>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106175 >>>>> >>>>> Cc: Leo Li <sunpeng...@amd.com> >>>>> Cc: Harry Wentland <harry.wentl...@amd.com> >>>>> Signed-off-by: Nicholas Kazlauskas <nicholas.kazlaus...@amd.com> >>>>> --- >>>>> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 67 >>>>> ++++++++++++++++++- >>>>> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 8 +++ >>>>> 2 files changed, 73 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>> index 23d61570df17..4df14a50a8ac 100644 >>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c >>>>> @@ -57,6 +57,7 @@ >>>>> >>>>> #include <drm/drmP.h> >>>>> #include <drm/drm_atomic.h> >>>>> +#include <drm/drm_atomic_uapi.h> >>>>> #include <drm/drm_atomic_helper.h> >>>>> #include <drm/drm_dp_mst_helper.h> >>>>> #include <drm/drm_fb_helper.h> >>>>> @@ -133,6 +134,8 @@ static void amdgpu_dm_atomic_commit_tail(struct >>>>> drm_atomic_state *state); >>>>> static int amdgpu_dm_atomic_check(struct drm_device *dev, >>>>> struct drm_atomic_state *state); >>>>> >>>>> +static void handle_cursor_update(struct drm_plane *plane, >>>>> + struct drm_plane_state *old_plane_state); >>>>> >>>>> >>>>> >>>>> @@ -402,6 +405,8 @@ static int amdgpu_dm_init(struct amdgpu_device *adev) >>>>> /* Zero all the fields */ >>>>> memset(&init_data, 0, sizeof(init_data)); >>>>> >>>>> + mutex_init(&adev->dm.dc_lock); >>>>> + >>>>> if(amdgpu_dm_irq_init(adev)) { >>>>> DRM_ERROR("amdgpu: failed to initialize DM IRQ >>>>> support.\n"); >>>>> goto error; >>>>> @@ -516,6 +521,9 @@ static void amdgpu_dm_fini(struct amdgpu_device *adev) >>>>> /* DC Destroy TODO: Replace destroy DAL */ >>>>> if (adev->dm.dc) >>>>> dc_destroy(&adev->dm.dc); >>>>> + >>>>> + mutex_destroy(&adev->dm.dc_lock); >>>>> + >>>>> return; >>>>> } >>>>> >>>>> @@ -3615,10 +3623,43 @@ static int dm_plane_atomic_check(struct drm_plane >>>>> *plane, >>>>> return -EINVAL; >>>>> } >>>>> >>>>> +static int dm_plane_atomic_async_check(struct drm_plane *plane, >>>>> + struct drm_plane_state *new_plane_state) >>>>> +{ >>>>> + /* Only support async updates on cursor planes. */ >>>>> + if (plane->type != DRM_PLANE_TYPE_CURSOR) >>>>> + return -EINVAL; >>>>> + >>>>> + return 0; >>>>> +} >>>>> + >>>>> +static void dm_plane_atomic_async_update(struct drm_plane *plane, >>>>> + struct drm_plane_state *new_state) >>>>> +{ >>>>> + struct drm_plane_state *old_state = >>>>> + drm_atomic_get_old_plane_state(new_state->state, plane); >>>>> + >>>>> + if (plane->state->fb != new_state->fb) >>>>> + drm_atomic_set_fb_for_plane(plane->state, new_state->fb); >>>>> + >>>>> + plane->state->src_x = new_state->src_x; >>>>> + plane->state->src_y = new_state->src_y; >>>>> + plane->state->src_w = new_state->src_w; >>>>> + plane->state->src_h = new_state->src_h; >>>>> + plane->state->crtc_x = new_state->crtc_x; >>>>> + plane->state->crtc_y = new_state->crtc_y; >>>>> + plane->state->crtc_w = new_state->crtc_w; >>>>> + plane->state->crtc_h = new_state->crtc_h; >>>>> + >>>>> + handle_cursor_update(plane, old_state); >>>>> +} >>>>> + >>>>> static const struct drm_plane_helper_funcs dm_plane_helper_funcs = { >>>>> .prepare_fb = dm_plane_helper_prepare_fb, >>>>> .cleanup_fb = dm_plane_helper_cleanup_fb, >>>>> .atomic_check = dm_plane_atomic_check, >>>>> + .atomic_async_check = dm_plane_atomic_async_check, >>>>> + .atomic_async_update = dm_plane_atomic_async_update >>>>> }; >>>>> >>>>> /* >>>>> @@ -4307,6 +4348,7 @@ static int get_cursor_position(struct drm_plane >>>>> *plane, struct drm_crtc *crtc, >>>>> static void handle_cursor_update(struct drm_plane *plane, >>>>> struct drm_plane_state >>>>> *old_plane_state) >>>>> { >>>>> + struct amdgpu_device *adev = plane->dev->dev_private; >>>>> struct amdgpu_framebuffer *afb = >>>>> to_amdgpu_framebuffer(plane->state->fb); >>>>> struct drm_crtc *crtc = afb ? plane->state->crtc : >>>>> old_plane_state->crtc; >>>>> struct dm_crtc_state *crtc_state = crtc ? >>>>> to_dm_crtc_state(crtc->state) : NULL; >>>>> @@ -4331,9 +4373,12 @@ static void handle_cursor_update(struct drm_plane >>>>> *plane, >>>>> >>>>> if (!position.enable) { >>>>> /* turn off cursor */ >>>>> - if (crtc_state && crtc_state->stream) >>>>> + if (crtc_state && crtc_state->stream) { >>>>> + mutex_lock(&adev->dm.dc_lock); >>>>> >>>>> dc_stream_set_cursor_position(crtc_state->stream, >>>>> &position); >>>>> + mutex_unlock(&adev->dm.dc_lock); >>>>> + } >>>>> return; >>>>> } >>>>> >>>>> @@ -4351,6 +4396,7 @@ static void handle_cursor_update(struct drm_plane >>>>> *plane, >>>>> attributes.pitch = attributes.width; >>>>> >>>>> if (crtc_state->stream) { >>>>> + mutex_lock(&adev->dm.dc_lock); >>>>> if (!dc_stream_set_cursor_attributes(crtc_state->stream, >>>>> &attributes)) >>>>> DRM_ERROR("DC failed to set cursor >>>>> attributes\n"); >>>>> @@ -4358,6 +4404,7 @@ static void handle_cursor_update(struct drm_plane >>>>> *plane, >>>>> if (!dc_stream_set_cursor_position(crtc_state->stream, >>>>> &position)) >>>>> DRM_ERROR("DC failed to set cursor position\n"); >>>>> + mutex_unlock(&adev->dm.dc_lock); >>>>> } >>>>> } >>>>> >>>>> @@ -4573,6 +4620,7 @@ static void amdgpu_dm_do_flip(struct drm_crtc *crtc, >>>>> &acrtc_state->stream->vrr_infopacket; >>>>> } >>>>> >>>>> + mutex_lock(&adev->dm.dc_lock); >>>>> dc_commit_updates_for_stream(adev->dm.dc, >>>>> surface_updates, >>>>> 1, >>>>> @@ -4580,6 +4628,7 @@ static void amdgpu_dm_do_flip(struct drm_crtc *crtc, >>>>> &stream_update, >>>>> &surface_updates->surface, >>>>> state); >>>>> + mutex_unlock(&adev->dm.dc_lock); >>>>> >>>>> DRM_DEBUG_DRIVER("%s Flipping to hi: 0x%x, low: 0x%x \n", >>>>> __func__, >>>>> @@ -4594,6 +4643,7 @@ static void amdgpu_dm_do_flip(struct drm_crtc *crtc, >>>>> * with a dc_plane_state and follow the atomic model a bit more >>>>> closely here. >>>>> */ >>>>> static bool commit_planes_to_stream( >>>>> + struct amdgpu_display_manager *dm, >>>>> struct dc *dc, >>>>> struct dc_plane_state **plane_states, >>>>> uint8_t new_plane_count, >>>>> @@ -4670,11 +4720,13 @@ static bool commit_planes_to_stream( >>>>> updates[i].scaling_info = &scaling_info[i]; >>>>> } >>>>> >>>>> + mutex_lock(&dm->dc_lock); >>>>> dc_commit_updates_for_stream( >>>>> dc, >>>>> updates, >>>>> new_plane_count, >>>>> dc_stream, stream_update, plane_states, state); >>>>> + mutex_unlock(&dm->dc_lock); >>>>> >>>>> kfree(flip_addr); >>>>> kfree(plane_info); >>>>> @@ -4780,7 +4832,8 @@ static void amdgpu_dm_commit_planes(struct >>>>> drm_atomic_state *state, >>>>> >>>>> dc_stream_attach->abm_level = acrtc_state->abm_level; >>>>> >>>>> - if (false == commit_planes_to_stream(dm->dc, >>>>> + if (false == commit_planes_to_stream(dm, >>>>> + dm->dc, >>>>> >>>>> plane_states_constructed, >>>>> planes_count, >>>>> acrtc_state, >>>>> @@ -4950,7 +5003,9 @@ static void amdgpu_dm_atomic_commit_tail(struct >>>>> drm_atomic_state *state) >>>>> >>>>> if (dc_state) { >>>>> dm_enable_per_frame_crtc_master_sync(dc_state); >>>>> + mutex_lock(&dm->dc_lock); >>>>> WARN_ON(!dc_commit_state(dm->dc, dc_state)); >>>>> + mutex_unlock(&dm->dc_lock); >>>>> } >>>>> >>>>> for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) { >>>>> @@ -5012,6 +5067,7 @@ static void amdgpu_dm_atomic_commit_tail(struct >>>>> drm_atomic_state *state) >>>>> >>>>> /*TODO How it works with MPO ?*/ >>>>> if (!commit_planes_to_stream( >>>>> + dm, >>>>> dm->dc, >>>>> status->plane_states, >>>>> status->plane_count, >>>>> @@ -5904,6 +5960,13 @@ static int amdgpu_dm_atomic_check(struct >>>>> drm_device *dev, >>>>> ret = -EINVAL; >>>>> goto fail; >>>>> } >>>>> + } else if (state->legacy_cursor_update) { >>>>> + /* >>>>> + * This is a fast cursor update coming from the plane update >>>>> + * helper, check if it can be done asynchronously for better >>>>> + * performance. >>>>> + */ >>>>> + state->async_update = !drm_atomic_helper_async_check(dev, >>>>> state); >>>>> } >>>>> >>>>> /* Must be success */ >>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h >>>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h >>>>> index 4326dc256491..25bb91ee80ba 100644 >>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h >>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h >>>>> @@ -134,6 +134,14 @@ struct amdgpu_display_manager { >>>>> >>>>> struct drm_modeset_lock atomic_obj_lock; >>>>> >>>>> + /** >>>>> + * @dc_lock: >>>>> + * >>>>> + * Guards access to DC functions that can issue register write >>>>> + * sequences. >>>>> + */ >>>>> + struct mutex dc_lock; >>>>> + >>>>> /** >>>>> * @irq_handler_list_low_tab: >>>>> * >> > _______________________________________________ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
