We are about to replace the single-linked bridge list by a double-linked
one based on list.h, leading to the suppression of the encoder->bridge
field. But before we can do that we must provide a
drm_bridge_chain_get_first_bridge() bridge helper and patch all drivers
and core helpers to use it instead of directly accessing encoder->bridge.

Note that we still have 2 drivers (VC4 and Exynos) manipulating the
encoder->bridge field directly because they need to cut the bridge chain
in order to control the enable/disable sequence. This is definitely
not something we want to encourage, so let's keep those 2 oddities
around until we find a better solution.

Signed-off-by: Boris Brezillon <boris.brezil...@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
Reviewed-by: Neil Armstrong <narmstr...@baylibre.com>
---
Changes in v4:
* Coding style issues
* Add Rbs
* Adjust the commit message to explain why VC4 and exynos still
  access encoder->bridge directly

Changes in v3:
* None

Changes in v2:
* None
---
 drivers/gpu/drm/drm_atomic_helper.c    | 26 +++++++++++++++++---------
 drivers/gpu/drm/drm_encoder.c          |  3 ++-
 drivers/gpu/drm/drm_probe_helper.c     |  4 +++-
 drivers/gpu/drm/msm/edp/edp_bridge.c   | 10 ++++++++--
 drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 10 +++++++---
 include/drm/drm_bridge.h               | 15 +++++++++++++++
 6 files changed, 52 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
b/drivers/gpu/drm/drm_atomic_helper.c
index cf678be58fa4..29c3115bf9e2 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -419,6 +419,7 @@ 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;
                struct drm_encoder *encoder;
+               struct drm_bridge *bridge;
 
                WARN_ON(!!new_conn_state->best_encoder != 
!!new_conn_state->crtc);
 
@@ -435,7 +436,8 @@ mode_fixup(struct drm_atomic_state *state)
                encoder = new_conn_state->best_encoder;
                funcs = encoder->helper_private;
 
-               ret = drm_bridge_chain_mode_fixup(encoder->bridge,
+               bridge = drm_bridge_chain_get_first_bridge(encoder);
+               ret = drm_bridge_chain_mode_fixup(bridge,
                                        &new_crtc_state->mode,
                                        &new_crtc_state->adjusted_mode);
                if (!ret) {
@@ -493,6 +495,7 @@ static enum drm_mode_status mode_valid_path(struct 
drm_connector *connector,
                                            struct drm_crtc *crtc,
                                            const struct drm_display_mode *mode)
 {
+       struct drm_bridge *bridge;
        enum drm_mode_status ret;
 
        ret = drm_encoder_mode_valid(encoder, mode);
@@ -502,7 +505,8 @@ static enum drm_mode_status mode_valid_path(struct 
drm_connector *connector,
                return ret;
        }
 
-       ret = drm_bridge_chain_mode_valid(encoder->bridge, mode);
+       bridge = drm_bridge_chain_get_first_bridge(encoder);
+       ret = drm_bridge_chain_mode_valid(bridge, mode);
        if (ret != MODE_OK) {
                DRM_DEBUG_ATOMIC("[BRIDGE] mode_valid() failed\n");
                return ret;
@@ -985,6 +989,7 @@ disable_outputs(struct drm_device *dev, struct 
drm_atomic_state *old_state)
        for_each_oldnew_connector_in_state(old_state, connector, 
old_conn_state, new_conn_state, i) {
                const struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
+               struct drm_bridge *bridge;
 
                /* Shut down everything that's in the changeset and currently
                 * still on. So need to check the old, saved state. */
@@ -1021,7 +1026,8 @@ disable_outputs(struct drm_device *dev, struct 
drm_atomic_state *old_state)
                 * Each encoder has at most one connector (since we always steal
                 * it away), so we won't call disable hooks twice.
                 */
-               drm_atomic_bridge_chain_disable(encoder->bridge, old_state);
+               bridge = drm_bridge_chain_get_first_bridge(encoder);
+               drm_atomic_bridge_chain_disable(bridge, old_state);
 
                /* Right function depends upon target state. */
                if (funcs) {
@@ -1035,8 +1041,7 @@ disable_outputs(struct drm_device *dev, struct 
drm_atomic_state *old_state)
                                funcs->dpms(encoder, DRM_MODE_DPMS_OFF);
                }
 
-               drm_atomic_bridge_chain_post_disable(encoder->bridge,
-                                                    old_state);
+               drm_atomic_bridge_chain_post_disable(bridge, old_state);
        }
 
        for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, 
new_crtc_state, i) {
@@ -1190,6 +1195,7 @@ crtc_set_mode(struct drm_device *dev, struct 
drm_atomic_state *old_state)
                const struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
                struct drm_display_mode *mode, *adjusted_mode;
+               struct drm_bridge *bridge;
 
                if (!new_conn_state->best_encoder)
                        continue;
@@ -1217,8 +1223,8 @@ crtc_set_mode(struct drm_device *dev, struct 
drm_atomic_state *old_state)
                        funcs->mode_set(encoder, mode, adjusted_mode);
                }
 
-               drm_bridge_chain_mode_set(encoder->bridge, mode,
-                                         adjusted_mode);
+               bridge = drm_bridge_chain_get_first_bridge(encoder);
+               drm_bridge_chain_mode_set(bridge, mode, adjusted_mode);
        }
 }
 
@@ -1317,6 +1323,7 @@ void drm_atomic_helper_commit_modeset_enables(struct 
drm_device *dev,
        for_each_new_connector_in_state(old_state, connector, new_conn_state, 
i) {
                const struct drm_encoder_helper_funcs *funcs;
                struct drm_encoder *encoder;
+               struct drm_bridge *bridge;
 
                if (!new_conn_state->best_encoder)
                        continue;
@@ -1335,7 +1342,8 @@ void drm_atomic_helper_commit_modeset_enables(struct 
drm_device *dev,
                 * Each encoder has at most one connector (since we always steal
                 * it away), so we won't call enable hooks twice.
                 */
-               drm_atomic_bridge_chain_pre_enable(encoder->bridge, old_state);
+               bridge = drm_bridge_chain_get_first_bridge(encoder);
+               drm_atomic_bridge_chain_pre_enable(bridge, old_state);
 
                if (funcs) {
                        if (funcs->atomic_enable)
@@ -1346,7 +1354,7 @@ void drm_atomic_helper_commit_modeset_enables(struct 
drm_device *dev,
                                funcs->commit(encoder);
                }
 
-               drm_atomic_bridge_chain_enable(encoder->bridge, old_state);
+               drm_atomic_bridge_chain_enable(bridge, old_state);
        }
 
        drm_atomic_helper_commit_writebacks(dev, old_state);
diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
index fcd3af1ac432..a2cc7e7241a9 100644
--- a/drivers/gpu/drm/drm_encoder.c
+++ b/drivers/gpu/drm/drm_encoder.c
@@ -167,9 +167,10 @@ void drm_encoder_cleanup(struct drm_encoder *encoder)
         */
 
        if (encoder->bridge) {
-               struct drm_bridge *bridge = encoder->bridge;
+               struct drm_bridge *bridge;
                struct drm_bridge *next;
 
+               bridge = drm_bridge_chain_get_first_bridge(encoder);
                while (bridge) {
                        next = drm_bridge_get_next_bridge(bridge);
                        drm_bridge_detach(bridge);
diff --git a/drivers/gpu/drm/drm_probe_helper.c 
b/drivers/gpu/drm/drm_probe_helper.c
index c3ea722065c4..576b4b7dcd89 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -101,6 +101,7 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
 
        /* Step 2: Validate against encoders and crtcs */
        drm_connector_for_each_possible_encoder(connector, encoder) {
+               struct drm_bridge *bridge;
                struct drm_crtc *crtc;
 
                ret = drm_encoder_mode_valid(encoder, mode);
@@ -112,7 +113,8 @@ drm_mode_validate_pipeline(struct drm_display_mode *mode,
                        continue;
                }
 
-               ret = drm_bridge_chain_mode_valid(encoder->bridge, mode);
+               bridge = drm_bridge_chain_get_first_bridge(encoder);
+               ret = drm_bridge_chain_mode_valid(bridge, mode);
                if (ret != MODE_OK) {
                        /* There is also no point in continuing for crtc check
                         * here. */
diff --git a/drivers/gpu/drm/msm/edp/edp_bridge.c 
b/drivers/gpu/drm/msm/edp/edp_bridge.c
index 2950bba4aca9..b65b5cc2dba2 100644
--- a/drivers/gpu/drm/msm/edp/edp_bridge.c
+++ b/drivers/gpu/drm/msm/edp/edp_bridge.c
@@ -55,8 +55,14 @@ static void edp_bridge_mode_set(struct drm_bridge *bridge,
        DBG("set mode: " DRM_MODE_FMT, DRM_MODE_ARG(mode));
 
        list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
-               if ((connector->encoder != NULL) &&
-                       (connector->encoder->bridge == bridge)) {
+               struct drm_encoder *encoder = connector->encoder;
+               struct drm_bridge *first_bridge;
+
+               if (!connector->encoder)
+                       continue;
+
+               first_bridge = drm_bridge_chain_get_first_bridge(encoder);
+               if (bridge == first_bridge) {
                        msm_edp_ctrl_timing_cfg(edp->ctrl,
                                adjusted_mode, &connector->display_info);
                        break;
diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c 
b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
index 2da46e3dc4ae..f2ae4c410244 100644
--- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c
@@ -14,6 +14,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_device.h>
 #include <drm/drm_fb_cma_helper.h>
@@ -680,9 +681,10 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc 
*crtc,
                        rcdu->encoders[RCAR_DU_OUTPUT_LVDS0 + rcrtc->index];
                const struct drm_display_mode *mode =
                        &crtc->state->adjusted_mode;
+               struct drm_bridge *bridge;
 
-               rcar_lvds_clk_enable(encoder->base.bridge,
-                                    mode->clock * 1000);
+               bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
+               rcar_lvds_clk_enable(bridge, mode->clock * 1000);
        }
 
        rcar_du_crtc_start(rcrtc);
@@ -702,12 +704,14 @@ static void rcar_du_crtc_atomic_disable(struct drm_crtc 
*crtc,
            rstate->outputs == BIT(RCAR_DU_OUTPUT_DPAD0)) {
                struct rcar_du_encoder *encoder =
                        rcdu->encoders[RCAR_DU_OUTPUT_LVDS0 + rcrtc->index];
+               struct drm_bridge *bridge;
 
                /*
                 * Disable the LVDS clock output, see
                 * rcar_du_crtc_atomic_enable().
                 */
-               rcar_lvds_clk_disable(encoder->base.bridge);
+               bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
+               rcar_lvds_clk_disable(bridge);
        }
 
        spin_lock_irq(&crtc->dev->event_lock);
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 46fc17c63a44..bd78c256b1ed 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -25,6 +25,7 @@
 
 #include <linux/list.h>
 #include <linux/ctype.h>
+#include <drm/drm_encoder.h>
 #include <drm/drm_mode_object.h>
 #include <drm/drm_modes.h>
 
@@ -422,6 +423,20 @@ drm_bridge_get_next_bridge(struct drm_bridge *bridge)
        return bridge->next;
 }
 
+/**
+ * drm_bridge_chain_get_first_bridge() - Get the first bridge in the chain
+ * @encoder: encoder object
+ *
+ * RETURNS:
+ * the first bridge in the chain, or NULL if @encoder has no bridge attached
+ * to it.
+ */
+static inline struct drm_bridge *
+drm_bridge_chain_get_first_bridge(struct drm_encoder *encoder)
+{
+       return encoder->bridge;
+}
+
 bool drm_bridge_chain_mode_fixup(struct drm_bridge *bridge,
                                 const struct drm_display_mode *mode,
                                 struct drm_display_mode *adjusted_mode);
-- 
2.23.0

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