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Wed, 08 Jan 2025 09:53:53 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:5485:d4b2:c087:b497]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a1c84705esm53745644f8f.44.2025.01.08.09.53.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Jan 2025 09:53:53 -0800 (PST) Date: Wed, 8 Jan 2025 18:53:51 +0100 From: Simona Vetter To: Dmitry Baryshkov Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Clark , Abhinav Kumar , Sean Paul , Marijn Suijten , Chandan Uddaraju , Jeykumar Sankaran , Jordan Crouse , Sravanthi Kollukuduru , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Archit Taneja , Rajesh Yadav , linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, Simona Vetter Subject: Re: [PATCH 2/6] drm/atomic: prepare to check that drivers follow restrictions for needs_modeset Message-ID: Mail-Followup-To: Dmitry Baryshkov , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Clark , Abhinav Kumar , Sean Paul , Marijn Suijten , Chandan Uddaraju , Jeykumar Sankaran , Jordan Crouse , Sravanthi Kollukuduru , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Archit Taneja , Rajesh Yadav , linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org References: <20241222-drm-dirty-modeset-v1-0-0e76a53eceb9@linaro.org> <20241222-drm-dirty-modeset-v1-2-0e76a53eceb9@linaro.org> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241222-drm-dirty-modeset-v1-2-0e76a53eceb9@linaro.org> X-Operating-System: Linux phenom 6.12.3-amd64 On Sun, Dec 22, 2024 at 07:00:42AM +0200, Dmitry Baryshkov wrote: > Some drivers might fail to follow the restrictions documented for > drm_atomic_helper_check_modesets(). In order to catch such an issues, > add the drm_atomic_state->dirty_needs_modeset field and check it in > drm_atomic_check_only(). Make sure that neither of atomic_check() > callbacks can set that field without calling > drm_atomic_helper_check_modesets() again. > > Suggested-by: Simona Vetter > Signed-off-by: Dmitry Baryshkov Thanks a lot of creating this patch. But looking at it I'm not so sure I actually had a good idea, since there's still lots of ways for drivers to change drm_atomic_crtc_needs_modeset() that we miss. And trying to use an inverted bitfield of all crtc that we've run through in check_modeset, and then in atomic_check_only compare it against all crtc that need a modeset also has corner cases it gets wrong I think, like just not using the helpers in specific case, I think something like i915's fastset would trip that. Plus there's lots more corners that drivers have gotten creatively wrong, so I feel like really clear docs is the best we can do. So unless you think it was really useful to fix msm I feel like best to skip this. Apologies for making you put work in here :-/ -Sima > --- > drivers/gpu/drm/drm_atomic.c | 3 ++ > drivers/gpu/drm/drm_atomic_helper.c | 77 +++++++++++++++++++++++++++++++++---- > include/drm/drm_atomic.h | 10 +++++ > 3 files changed, 82 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c > index 9ea2611770f43ce7ccba410406d5f2c528aab022..202e4e64bd31921d0a4d4b86605b501311e14c33 100644 > --- a/drivers/gpu/drm/drm_atomic.c > +++ b/drivers/gpu/drm/drm_atomic.c > @@ -1449,6 +1449,9 @@ int drm_atomic_check_only(struct drm_atomic_state *state) > } > } > > + WARN_RATELIMIT(state->dirty_needs_modeset, > + "Driver changed needs_modeset under drm_atomic_helper_check_modeset()"); > + > if (!state->allow_modeset) { > for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) { > if (drm_atomic_crtc_needs_modeset(new_crtc_state)) { > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > index f26887c3fe8b194137200f9f2426653274c50fda..2c62840416f4b807d6a880b5c30ae024a16af528 100644 > --- a/drivers/gpu/drm/drm_atomic_helper.c > +++ b/drivers/gpu/drm/drm_atomic_helper.c > @@ -433,6 +433,7 @@ mode_fixup(struct drm_atomic_state *state) > > for_each_new_connector_in_state(state, connector, new_conn_state, i) { > const struct drm_encoder_helper_funcs *funcs; > + bool old_needs_modeset = false; > struct drm_encoder *encoder; > struct drm_bridge *bridge; > > @@ -451,6 +452,9 @@ mode_fixup(struct drm_atomic_state *state) > encoder = new_conn_state->best_encoder; > funcs = encoder->helper_private; > > + if (new_crtc_state) > + old_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > bridge = drm_bridge_chain_get_first_bridge(encoder); > ret = drm_atomic_bridge_chain_check(bridge, > new_crtc_state, > @@ -479,6 +483,12 @@ mode_fixup(struct drm_atomic_state *state) > return -EINVAL; > } > } > + > + if (new_crtc_state) { > + bool new_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > + state->dirty_needs_modeset |= (new_needs_modeset != old_needs_modeset); > + } > } > > for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) { > @@ -574,6 +584,36 @@ mode_valid(struct drm_atomic_state *state) > return 0; > } > > +static int > +connector_atomic_check(struct drm_atomic_state *state, > + struct drm_connector *connector, > + struct drm_connector_state *old_connector_state, > + struct drm_connector_state *new_connector_state) > +{ > + const struct drm_connector_helper_funcs *funcs = connector->helper_private; > + struct drm_crtc_state *new_crtc_state; > + bool old_needs_modeset = false; > + int ret; > + > + if (new_connector_state->crtc) > + new_crtc_state = drm_atomic_get_new_crtc_state(state, new_connector_state->crtc); > + if (new_crtc_state) > + old_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > + if (funcs->atomic_check) > + ret = funcs->atomic_check(connector, state); > + else > + ret = 0; > + > + if (new_crtc_state) { > + bool new_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > + state->dirty_needs_modeset |= (new_needs_modeset != old_needs_modeset); > + } > + > + return ret; > +} > + > /** > * drm_atomic_helper_check_modeset - validate state object for modeset changes > * @dev: DRM device > @@ -628,6 +668,8 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, > int i, ret; > unsigned int connectors_mask = 0, user_connectors_mask = 0; > > + state->dirty_needs_modeset = false; > + > for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) > user_connectors_mask |= BIT(i); > > @@ -683,8 +725,6 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, > return ret; > > for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) { > - const struct drm_connector_helper_funcs *funcs = connector->helper_private; > - > WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex)); > > /* > @@ -710,8 +750,8 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, > new_crtc_state->connectors_changed = true; > } > > - if (funcs->atomic_check) > - ret = funcs->atomic_check(connector, state); > + ret = connector_atomic_check(state, connector, > + old_connector_state, new_connector_state); > if (ret) { > drm_dbg_atomic(dev, > "[CONNECTOR:%d:%s] driver check failed\n", > @@ -752,13 +792,11 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, > * has been called on them when a modeset is forced. > */ > for_each_oldnew_connector_in_state(state, connector, old_connector_state, new_connector_state, i) { > - const struct drm_connector_helper_funcs *funcs = connector->helper_private; > - > if (connectors_mask & BIT(i)) > continue; > > - if (funcs->atomic_check) > - ret = funcs->atomic_check(connector, state); > + ret = connector_atomic_check(state, connector, > + old_connector_state, new_connector_state); > if (ret) { > drm_dbg_atomic(dev, > "[CONNECTOR:%d:%s] driver check failed\n", > @@ -994,6 +1032,7 @@ drm_atomic_helper_check_planes(struct drm_device *dev, > > for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) { > const struct drm_plane_helper_funcs *funcs; > + bool old_needs_modeset = false; > > WARN_ON(!drm_modeset_is_locked(&plane->mutex)); > > @@ -1006,6 +1045,12 @@ drm_atomic_helper_check_planes(struct drm_device *dev, > if (!funcs || !funcs->atomic_check) > continue; > > + if (new_plane_state->crtc) > + new_crtc_state = drm_atomic_get_new_crtc_state(state, > + new_plane_state->crtc); > + if (new_crtc_state) > + old_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > ret = funcs->atomic_check(plane, state); > if (ret) { > drm_dbg_atomic(plane->dev, > @@ -1013,16 +1058,26 @@ drm_atomic_helper_check_planes(struct drm_device *dev, > plane->base.id, plane->name); > return ret; > } > + > + if (new_crtc_state) { > + bool new_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > + state->dirty_needs_modeset |= (new_needs_modeset != old_needs_modeset); > + } > } > > for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) { > const struct drm_crtc_helper_funcs *funcs; > + bool old_needs_modeset = false; > > funcs = crtc->helper_private; > > if (!funcs || !funcs->atomic_check) > continue; > > + if (new_crtc_state) > + old_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > ret = funcs->atomic_check(crtc, state); > if (ret) { > drm_dbg_atomic(crtc->dev, > @@ -1030,6 +1085,12 @@ drm_atomic_helper_check_planes(struct drm_device *dev, > crtc->base.id, crtc->name); > return ret; > } > + > + if (new_crtc_state) { > + bool new_needs_modeset = drm_atomic_crtc_needs_modeset(new_crtc_state); > + > + state->dirty_needs_modeset |= (new_needs_modeset != old_needs_modeset); > + } > } > > return ret; > diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h > index 31ca88deb10d262fb3a3f8e14d2afe24f8410cb1..7b0dbd3c8a3df340399a458aaf79263f0fdc24e5 100644 > --- a/include/drm/drm_atomic.h > +++ b/include/drm/drm_atomic.h > @@ -408,6 +408,16 @@ struct drm_atomic_state { > */ > bool duplicated : 1; > > + /** > + * @dirty_needs_modeset: > + * > + * Indicates whether the drm_atomic_crtc_needs_modeset() changed in an > + * unexpected way. Usually this means that driver implements atomic > + * helpers using drm_atomic_crtc_needs_modeset(), but mode_changed has > + * toggled by one of its atomic_check() callbacks. > + */ > + bool dirty_needs_modeset : 1; > + > /** > * @planes: > * > > -- > 2.39.5 > -- Simona Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch