On 2020-01-22 12:16, Boris Brezillon wrote: > drm_bridge_state is extended to describe the input and output bus > configurations. These bus configurations are exposed through the > drm_bus_cfg struct which encodes the configuration of a physical > bus between two components in an output pipeline, usually between > two bridges, an encoder and a bridge, or a bridge and a connector. > > The bus configuration is stored in drm_bridge_state separately for > the input and output buses, as seen from the point of view of each > bridge. The bus configuration of a bridge output is usually identical > to the configuration of the next bridge's input, but may differ if > the signals are modified between the two bridges, for instance by an > inverter on the board. The input and output configurations of a > bridge may differ if the bridge modifies the signals internally, > for instance by performing format conversion, or*modifying signals > polarities. > > Bus format negotiation is automated by the core, drivers just have > to implement the ->atomic_get_{output,input}_bus_fmts() hooks if they > want to take part to this negotiation. Negotiation happens in reverse > order, starting from the last element of the chain (the one directly > connected to the display) up to the first element of the chain (the one > connected to the encoder). > During this negotiation all supported formats are tested until we find > one that works, meaning that the formats array should be in decreasing > preference order (assuming the driver has a preference order). > > Note that the bus format negotiation works even if some elements in the > chain don't implement the ->atomic_get_{output,input}_bus_fmts() hooks. > In that case, the core advertises only MEDIA_BUS_FMT_FIXED and lets > the previous bridge element decide what to do (most of the time, bridge > drivers will pick a default bus format or extract this piece of > information from somewhere else, like a FW property). > > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> > Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx> > [narmstrong: fixed doc in include/drm/drm_bridge.h:69 fmt->format] > Reviewed by: Jernej Skrabec <jernej.skrabec@xxxxxxxx> > Tested-by: Jonas Karlman <jonas@xxxxxxxxx> > --- > Changes in v7: > * Adapt the code to deal with the fact that not all bridges in the > chain have a bridge state > --- > drivers/gpu/drm/drm_atomic_helper.c | 41 +++++ > drivers/gpu/drm/drm_bridge.c | 253 +++++++++++++++++++++++++++- > include/drm/drm_atomic.h | 42 +++++ > include/drm/drm_atomic_helper.h | 8 + > include/drm/drm_bridge.h | 82 +++++++++ > 5 files changed, 425 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > index afe14f72a824..ea1926b5bb80 100644 > --- a/drivers/gpu/drm/drm_atomic_helper.c > +++ b/drivers/gpu/drm/drm_atomic_helper.c > @@ -3528,3 +3528,44 @@ int drm_atomic_helper_legacy_gamma_set(struct drm_crtc *crtc, > return ret; > } > EXPORT_SYMBOL(drm_atomic_helper_legacy_gamma_set); > + > +/** > + * drm_atomic_helper_bridge_propagate_bus_fmt() - Propagate output format to > + * the input end of a bridge > + * @bridge: bridge control structure > + * @bridge_state: new bridge state > + * @crtc_state: new CRTC state > + * @conn_state: new connector state > + * @output_fmt: tested output bus format > + * @num_input_fmts: will contain the size of the returned array > + * > + * This helper is a pluggable implementation of the > + * &drm_bridge_funcs.atomic_get_input_bus_fmts operation for bridges that don't > + * modify the bus configuration between their input and their output. It > + * returns an array of input formats with a single element set to @output_fmt. > + * > + * RETURNS: > + * a valid format array of size @num_input_fmts, or NULL if the allocation > + * failed > + */ > +u32 * > +drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge, > + struct drm_bridge_state *bridge_state, > + struct drm_crtc_state *crtc_state, > + struct drm_connector_state *conn_state, > + u32 output_fmt, > + unsigned int *num_input_fmts) > +{ > + u32 *input_fmts; > + > + input_fmts = kzalloc(sizeof(*input_fmts), GFP_KERNEL); > + if (!input_fmts) { > + *num_input_fmts = 0; > + return NULL; > + } > + > + *num_input_fmts = 1; > + input_fmts[0] = output_fmt; > + return input_fmts; > +} > +EXPORT_SYMBOL(drm_atomic_helper_bridge_propagate_bus_fmt); > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c > index dd3a2a9f87d3..0c28816146ba 100644 > --- a/drivers/gpu/drm/drm_bridge.c > +++ b/drivers/gpu/drm/drm_bridge.c > @@ -598,13 +598,247 @@ static int drm_atomic_bridge_check(struct drm_bridge *bridge, > return 0; > } > > +static int select_bus_fmt_recursive(struct drm_bridge *first_bridge, > + struct drm_bridge *cur_bridge, > + struct drm_crtc_state *crtc_state, > + struct drm_connector_state *conn_state, > + u32 out_bus_fmt) > +{ > + struct drm_bridge_state *cur_state; > + unsigned int num_in_bus_fmts, i; > + struct drm_bridge *prev_bridge; > + u32 *in_bus_fmts; > + int ret; > + > + prev_bridge = drm_bridge_get_prev_bridge(cur_bridge); > + cur_state = drm_atomic_get_new_bridge_state(crtc_state->state, > + cur_bridge); > + > + /* > + * If bus format negotiation is not supported by this bridge, let's > + * pass MEDIA_BUS_FMT_FIXED to the previous bridge in the chain and > + * hope that it can handle this situation gracefully (by providing > + * appropriate default values). > + */ > + if (!cur_bridge->funcs->atomic_get_input_bus_fmts) { > + if (cur_bridge != first_bridge) { > + ret = select_bus_fmt_recursive(first_bridge, > + prev_bridge, crtc_state, > + conn_state, > + MEDIA_BUS_FMT_FIXED); > + if (ret) > + return ret; > + } > + > + /* > + * Driver does not implement the atomic state hooks, but that's > + * fine, as long as it does not access the bridge state. > + */ > + if (cur_state) { > + cur_state->input_bus_cfg.format = MEDIA_BUS_FMT_FIXED; > + cur_state->output_bus_cfg.format = out_bus_fmt; > + } > + > + return 0; > + } > + > + /* > + * If the driver implements ->atomic_get_input_bus_fmts() it > + * should also implement the atomic state hooks. > + */ > + if (WARN_ON(!cur_state)) > + return -EINVAL; > + > + in_bus_fmts = cur_bridge->funcs->atomic_get_input_bus_fmts(cur_bridge, > + cur_state, > + crtc_state, > + conn_state, > + out_bus_fmt, > + &num_in_bus_fmts); > + if (!num_in_bus_fmts) > + return -ENOTSUPP; > + else if (!in_bus_fmts) > + return -ENOMEM; > + > + if (first_bridge == cur_bridge) { > + cur_state->input_bus_cfg.format = in_bus_fmts[0]; > + cur_state->output_bus_cfg.format = out_bus_fmt; > + kfree(in_bus_fmts); > + return 0; > + } > + > + for (i = 0; i < num_in_bus_fmts; i++) { > + ret = select_bus_fmt_recursive(first_bridge, prev_bridge, > + crtc_state, conn_state, > + in_bus_fmts[i]); > + if (ret != -ENOTSUPP) > + break; > + } > + > + if (!ret) { > + cur_state->input_bus_cfg.format = in_bus_fmts[i]; > + cur_state->output_bus_cfg.format = out_bus_fmt; > + } > + > + kfree(in_bus_fmts); > + return ret; > +} > + > +/* > + * This function is called by &drm_atomic_bridge_chain_check() just before > + * calling &drm_bridge_funcs.atomic_check() on all elements of the chain. > + * It performs bus format negotiation between bridge elements. The negotiation > + * happens in reverse order, starting from the last element in the chain up to > + * @bridge. > + * > + * Negotiation starts by retrieving supported output bus formats on the last > + * bridge element and testing them one by one. The test is recursive, meaning > + * that for each tested output format, the whole chain will be walked backward, > + * and each element will have to choose an input bus format that can be > + * transcoded to the requested output format. When a bridge element does not > + * support transcoding into a specific output format -ENOTSUPP is returned and > + * the next bridge element will have to try a different format. If none of the > + * combinations worked, -ENOTSUPP is returned and the atomic modeset will fail. > + * > + * This implementation is relying on > + * &drm_bridge_funcs.atomic_get_output_bus_fmts() and > + * &drm_bridge_funcs.atomic_get_input_bus_fmts() to gather supported > + * input/output formats. > + * > + * When &drm_bridge_funcs.atomic_get_output_bus_fmts() is not implemented by > + * the last element of the chain, &drm_atomic_bridge_chain_select_bus_fmts() > + * tries a single format: &drm_connector.display_info.bus_formats[0] if > + * available, MEDIA_BUS_FMT_FIXED otherwise. > + * > + * When &drm_bridge_funcs.atomic_get_input_bus_fmts() is not implemented, > + * &drm_atomic_bridge_chain_select_bus_fmts() skips the negotiation on the > + * bridge element that lacks this hook and asks the previous element in the > + * chain to try MEDIA_BUS_FMT_FIXED. It's up to bridge drivers to decide what > + * to do in that case (fail if they want to enforce bus format negotiation, or > + * provide a reasonable default if they need to support pipelines where not > + * all elements support bus format negotiation). > + */ > +static int > +drm_atomic_bridge_chain_select_bus_fmts(struct drm_bridge *bridge, > + struct drm_crtc_state *crtc_state, > + struct drm_connector_state *conn_state) > +{ > + struct drm_connector *conn = conn_state->connector; > + struct drm_encoder *encoder = bridge->encoder; > + struct drm_bridge_state *last_bridge_state; > + unsigned int i, num_out_bus_fmts; > + struct drm_bridge *last_bridge; > + u32 *out_bus_fmts; > + int ret = 0; > + > + last_bridge = list_last_entry(&encoder->bridge_chain, > + struct drm_bridge, chain_node); > + last_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state, > + last_bridge); > + > + if (last_bridge->funcs->atomic_get_output_bus_fmts) { > + const struct drm_bridge_funcs *funcs = last_bridge->funcs; > + > + /* > + * If the driver implements ->atomic_get_output_bus_fmts() it > + * should also implement the atomic state hooks. > + */ > + if (WARN_ON(last_bridge_state)) This looks wrong, with this changed to WARN_ON(!last_bridge_state) my RK3328 HDMI2.0/YUV444/YUV420/10-bit branch at [1] starts working. With WARN_ON(last_bridge_state) I get: [ 6.606658] WARNING: CPU: 0 PID: 167 at drivers/gpu/drm/drm_bridge.c:746 drm_atomic_bridge_chain_check+0x2b8/0x308 [ 6.606673] Hardware name: Pine64 Rock64 (DT) [ 6.606754] Call trace: [ 6.606759] drm_atomic_bridge_chain_check+0x2b8/0x308 [ 6.606764] drm_atomic_helper_check_modeset+0x89c/0xab8 [ 6.606768] drm_atomic_helper_check+0x1c/0xa0 [ 6.606772] drm_atomic_check_only+0x464/0x708 [ 6.606777] drm_atomic_commit+0x18/0x58 [1] https://github.com/Kwiboo/linux-rockchip/commits/next-20200122-bus-format Regards, Jonas > + return -EINVAL; > + > + out_bus_fmts = funcs->atomic_get_output_bus_fmts(last_bridge, > + last_bridge_state, > + crtc_state, > + conn_state, > + &num_out_bus_fmts); > + if (!num_out_bus_fmts) > + return -ENOTSUPP; > + else if (!out_bus_fmts) > + return -ENOMEM; > + } else { > + num_out_bus_fmts = 1; > + out_bus_fmts = kmalloc(sizeof(*out_bus_fmts), GFP_KERNEL); > + if (!out_bus_fmts) > + return -ENOMEM; > + > + if (conn->display_info.num_bus_formats && > + conn->display_info.bus_formats) > + out_bus_fmts[0] = conn->display_info.bus_formats[0]; > + else > + out_bus_fmts[0] = MEDIA_BUS_FMT_FIXED; > + } > + > + for (i = 0; i < num_out_bus_fmts; i++) { > + ret = select_bus_fmt_recursive(bridge, last_bridge, crtc_state, > + conn_state, out_bus_fmts[i]); > + if (ret != -ENOTSUPP) > + break; > + } > + > + kfree(out_bus_fmts); > + > + return ret; > +} > + > +static void > +drm_atomic_bridge_propagate_bus_flags(struct drm_bridge *bridge, > + struct drm_connector *conn, > + struct drm_atomic_state *state) > +{ > + struct drm_bridge_state *bridge_state, *next_bridge_state; > + struct drm_bridge *next_bridge; > + u32 output_flags = 0; > + > + bridge_state = drm_atomic_get_new_bridge_state(state, bridge); > + > + /* No bridge state attached to this bridge => nothing to propagate. */ > + if (!bridge_state) > + return; > + > + next_bridge = drm_bridge_get_next_bridge(bridge); > + > + /* > + * Let's try to apply the most common case here, that is, propagate > + * display_info flags for the last bridge, and propagate the input > + * flags of the next bridge element to the output end of the current > + * bridge when the bridge is not the last one. > + * There are exceptions to this rule, like when signal inversion is > + * happening at the board level, but that's something drivers can deal > + * with from their &drm_bridge_funcs.atomic_check() implementation by > + * simply overriding the flags value we've set here. > + */ > + if (!next_bridge) { > + output_flags = conn->display_info.bus_flags; > + } else { > + next_bridge_state = drm_atomic_get_new_bridge_state(state, > + next_bridge); > + /* > + * No bridge state attached to the next bridge, just leave the > + * flags to 0. > + */ > + if (next_bridge_state) > + output_flags = next_bridge_state->input_bus_cfg.flags; > + } > + > + bridge_state->output_bus_cfg.flags = output_flags; > + > + /* > + * Propage the output flags to the input end of the bridge. Again, it's > + * not necessarily what all bridges want, but that's what most of them > + * do, and by doing that by default we avoid forcing drivers to > + * duplicate the "dummy propagation" logic. > + */ > + bridge_state->input_bus_cfg.flags = output_flags; > +} > + > /** > * drm_atomic_bridge_chain_check() - Do an atomic check on the bridge chain > * @bridge: bridge control structure > * @crtc_state: new CRTC state > * @conn_state: new connector state > * > - * Calls &drm_bridge_funcs.atomic_check() (falls back on > + * First trigger a bus format negotiation before calling > + * &drm_bridge_funcs.atomic_check() (falls back on > * &drm_bridge_funcs.mode_fixup()) op for all the bridges in the encoder chain, > * starting from the last bridge to the first. These are called before calling > * &drm_encoder_helper_funcs.atomic_check() > @@ -616,16 +850,33 @@ int drm_atomic_bridge_chain_check(struct drm_bridge *bridge, > struct drm_crtc_state *crtc_state, > struct drm_connector_state *conn_state) > { > + struct drm_connector *conn = conn_state->connector; > struct drm_encoder *encoder; > struct drm_bridge *iter; > + int ret; > > if (!bridge) > return 0; > > + ret = drm_atomic_bridge_chain_select_bus_fmts(bridge, crtc_state, > + conn_state); > + if (ret) > + return ret; > + > encoder = bridge->encoder; > list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) { > int ret; > > + /* > + * Bus flags are propagated by default. If a bridge needs to > + * tweak the input bus flags for any reason, it should happen > + * in its &drm_bridge_funcs.atomic_check() implementation such > + * that preceding bridges in the chain can propagate the new > + * bus flags. > + */ > + drm_atomic_bridge_propagate_bus_flags(iter, conn, > + crtc_state->state); > + > ret = drm_atomic_bridge_check(iter, crtc_state, conn_state); > if (ret) > return ret; > diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h > index 82a888769b3d..52d65a055491 100644 > --- a/include/drm/drm_atomic.h > +++ b/include/drm/drm_atomic.h > @@ -995,6 +995,38 @@ drm_atomic_crtc_effectively_active(const struct drm_crtc_state *state) > return state->active || state->self_refresh_active; > } > > +/** > + * struct drm_bus_cfg - bus configuration > + * > + * This structure stores the configuration of a physical bus between two > + * components in an output pipeline, usually between two bridges, an encoder > + * and a bridge, or a bridge and a connector. > + * > + * The bus configuration is stored in &drm_bridge_state separately for the > + * input and output buses, as seen from the point of view of each bridge. The > + * bus configuration of a bridge output is usually identical to the > + * configuration of the next bridge's input, but may differ if the signals are > + * modified between the two bridges, for instance by an inverter on the board. > + * The input and output configurations of a bridge may differ if the bridge > + * modifies the signals internally, for instance by performing format > + * conversion, or modifying signals polarities. > + */ > +struct drm_bus_cfg { > + /** > + * @format: format used on this bus (one of the MEDIA_BUS_FMT_* format) > + * > + * This field should not be directly modified by drivers > + * (&drm_atomic_bridge_chain_select_bus_fmts() takes care of the bus > + * format negotiation). > + */ > + u32 format; > + > + /** > + * @flags: DRM_BUS_* flags used on this bus > + */ > + u32 flags; > +}; > + > /** > * struct drm_bridge_state - Atomic bridge state object > */ > @@ -1008,6 +1040,16 @@ struct drm_bridge_state { > * @bridge: the bridge this state refers to > */ > struct drm_bridge *bridge; > + > + /** > + * @input_bus_cfg: input bus configuration > + */ > + struct drm_bus_cfg input_bus_cfg; > + > + /** > + * @output_bus_cfg: input bus configuration > + */ > + struct drm_bus_cfg output_bus_cfg; > }; > > static inline struct drm_bridge_state * > diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h > index 9db3cac48f4f..b268180c97eb 100644 > --- a/include/drm/drm_atomic_helper.h > +++ b/include/drm/drm_atomic_helper.h > @@ -224,4 +224,12 @@ drm_atomic_plane_disabling(struct drm_plane_state *old_plane_state, > return old_plane_state->crtc && !new_plane_state->crtc; > } > > +u32 * > +drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge, > + struct drm_bridge_state *bridge_state, > + struct drm_crtc_state *crtc_state, > + struct drm_connector_state *conn_state, > + u32 output_fmt, > + unsigned int *num_input_fmts); > + > #endif /* DRM_ATOMIC_HELPER_H_ */ > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h > index 04815ab948dd..e9f407993c8b 100644 > --- a/include/drm/drm_bridge.h > +++ b/include/drm/drm_bridge.h > @@ -370,6 +370,72 @@ struct drm_bridge_funcs { > void (*atomic_destroy_state)(struct drm_bridge *bridge, > struct drm_bridge_state *state); > > + /** > + * @atomic_get_output_bus_fmts: > + * > + * Return the supported bus formats on the output end of a bridge. > + * The returned array must be allocated with kmalloc() and will be > + * freed by the caller. If the allocation fails, NULL should be > + * returned. num_output_fmts must be set to the returned array size. > + * Formats listed in the returned array should be listed in decreasing > + * preference order (the core will try all formats until it finds one > + * that works). > + * > + * This method is only called on the last element of the bridge chain > + * as part of the bus format negotiation process that happens in > + * &drm_atomic_bridge_chain_select_bus_fmts(). > + * This method is optional. When not implemented, the core will > + * fall back to &drm_connector.display_info.bus_formats[0] if > + * &drm_connector.display_info.num_bus_formats > 0, > + * or to MEDIA_BUS_FMT_FIXED otherwise. > + */ > + u32 *(*atomic_get_output_bus_fmts)(struct drm_bridge *bridge, > + struct drm_bridge_state *bridge_state, > + struct drm_crtc_state *crtc_state, > + struct drm_connector_state *conn_state, > + unsigned int *num_output_fmts); > + > + /** > + * @atomic_get_input_bus_fmts: > + * > + * Return the supported bus formats on the input end of a bridge for > + * a specific output bus format. > + * > + * The returned array must be allocated with kmalloc() and will be > + * freed by the caller. If the allocation fails, NULL should be > + * returned. num_output_fmts must be set to the returned array size. > + * Formats listed in the returned array should be listed in decreasing > + * preference order (the core will try all formats until it finds one > + * that works). When the format is not supported NULL should be > + * returned and *num_output_fmts should be set to 0. > + * > + * This method is called on all elements of the bridge chain as part of > + * the bus format negotiation process that happens in > + * &drm_atomic_bridge_chain_select_bus_fmts(). > + * This method is optional. When not implemented, the core will bypass > + * bus format negotiation on this element of the bridge without > + * failing, and the previous element in the chain will be passed > + * MEDIA_BUS_FMT_FIXED as its output bus format. > + * > + * Bridge drivers that need to support being linked to bridges that are > + * not supporting bus format negotiation should handle the > + * output_fmt == MEDIA_BUS_FMT_FIXED case appropriately, by selecting a > + * sensible default value or extracting this information from somewhere > + * else (FW property, &drm_display_mode, &drm_display_info, ...) > + * > + * Note: Even if input format selection on the first bridge has no > + * impact on the negotiation process (bus format negotiation stops once > + * we reach the first element of the chain), drivers are expected to > + * return accurate input formats as the input format may be used to > + * configure the CRTC output appropriately. > + */ > + u32 *(*atomic_get_input_bus_fmts)(struct drm_bridge *bridge, > + struct drm_bridge_state *bridge_state, > + struct drm_crtc_state *crtc_state, > + struct drm_connector_state *conn_state, > + u32 output_fmt, > + unsigned int *num_input_fmts); > + > /** > * @atomic_check: > * > @@ -384,6 +450,14 @@ struct drm_bridge_funcs { > * called when &drm_bridge_funcs.atomic_check() is implemented, so only > * one of them should be provided. > * > + * If drivers need to tweak &drm_bridge_state.input_bus_cfg.flags or > + * &drm_bridge_state.output_bus_cfg.flags it should should happen in > + * this function. By default the &drm_bridge_state.output_bus_cfg.flags > + * field is set to the next bridge > + * &drm_bridge_state.input_bus_cfg.flags value or > + * &drm_connector.display_info.bus_flags if the bridge is the last > + * element in the chain. > + * > * RETURNS: > * zero if the check passed, a negative error code otherwise. > */ > @@ -571,6 +645,14 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge, > void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge, > struct drm_atomic_state *state); > > +u32 * > +drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge, > + struct drm_bridge_state *bridge_state, > + struct drm_crtc_state *crtc_state, > + struct drm_connector_state *conn_state, > + u32 output_fmt, > + unsigned int *num_input_fmts); > + > #ifdef CONFIG_DRM_PANEL_BRIDGE > struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel); > struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel, >