[PATCH 1/2] drm: Introduce DRM_BRIDGE_OP_UPSTREAM_FIRST to alter bridge init order
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Tue Feb 22 06:33:59 UTC 2022
Hi Dave,
Thank you for the patch.
On Wed, Feb 16, 2022 at 04:59:43PM +0000, Dave Stevenson wrote:
> DSI sink devices typically want the DSI host powered up and configured
> before they are powered up. pre_enable is the place this would normally
> happen, but they are called in reverse order from panel/connector towards
> the encoder, which is the "wrong" order.
>
> Add a new flag DRM_BRIDGE_OP_UPSTREAM_FIRST that any bridge can set
> to swap the order of pre_enable (and post_disable) so that any upstream
> bridges are called first to create the desired state.
>
> eg:
> - Panel
> - Bridge 1
> - Bridge 2 DRM_BRIDGE_OP_UPSTREAM_FIRST
> - Bridge 3
> - Encoder
> Would result in pre_enable's being called as Panel, Bridge 1, Bridge 3,
> Bridge 2.
If there was a Bridge 4 between Bridge 3 and Encoder, would it be
Panel, Bridge 1, Bridge 3, Bridge 4, Bridge 2
? I'd capture that here, to be explicit.
> Signed-off-by: Dave Stevenson <dave.stevenson at raspberrypi.com>
> ---
> drivers/gpu/drm/drm_bridge.c | 197 +++++++++++++++++++++++++++++++++++++------
> include/drm/drm_bridge.h | 8 ++
> 2 files changed, 180 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index c96847fc0ebc..7c24e8340efa 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -522,21 +522,58 @@ EXPORT_SYMBOL(drm_bridge_chain_disable);
> * Calls &drm_bridge_funcs.post_disable op for all the bridges in the
> * encoder chain, starting from the first bridge to the last. These are called
> * after completing the encoder's prepare op.
Missing blank line, as well as in three locations below.
> + * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the post_disable for
> + * that bridge will be called before the previous one to reverse the pre_enable
> + * calling direction.
> *
> * Note: the bridge passed should be the one closest to the encoder
> */
> void drm_bridge_chain_post_disable(struct drm_bridge *bridge)
> {
> struct drm_encoder *encoder;
> + struct drm_bridge *next, *limit;
>
> if (!bridge)
> return;
>
> encoder = bridge->encoder;
> list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
> + limit = NULL;
> +
> + if (!list_is_last(&bridge->chain_node, &encoder->bridge_chain)) {
> + next = list_next_entry(bridge, chain_node);
> +
> + if (next->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
> + limit = next;
> +
> + list_for_each_entry_from(next, &encoder->bridge_chain,
> + chain_node) {
> + if (!(next->ops &
> + DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
> + next = list_prev_entry(next, chain_node);
> + limit = next;
> + break;
> + }
> + }
> +
> + list_for_each_entry_from_reverse(next, &encoder->bridge_chain,
> + chain_node) {
> + if (next == bridge)
> + break;
> +
> + if (next->funcs->post_disable)
> + next->funcs->post_disable(next);
> + }
> + }
> + }
> +
> if (bridge->funcs->post_disable)
> bridge->funcs->post_disable(bridge);
> +
> + if (limit)
> + bridge = limit;
> }
> +
> }
> EXPORT_SYMBOL(drm_bridge_chain_post_disable);
>
> @@ -577,22 +614,53 @@ EXPORT_SYMBOL(drm_bridge_chain_mode_set);
> * Calls &drm_bridge_funcs.pre_enable op for all the bridges in the encoder
> * chain, starting from the last bridge to the first. These are called
> * before calling the encoder's commit op.
> + * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the pre_enable for
> + * the previous bridge will be called before pre_enable of this bridge.
> *
> * Note: the bridge passed should be the one closest to the encoder
> */
> void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
> {
> struct drm_encoder *encoder;
> - struct drm_bridge *iter;
> + struct drm_bridge *iter, *next, *limit;
>
> if (!bridge)
> return;
>
> encoder = bridge->encoder;
> +
> list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
> + if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
> + next = iter;
> + limit = bridge;
> + list_for_each_entry_from_reverse(next,
> + &encoder->bridge_chain,
> + chain_node) {
> + if (next == bridge)
> + break;
> +
> + if (!(next->ops &
> + DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
> + limit = list_prev_entry(next, chain_node);
> + break;
> + }
> + }
> +
> + list_for_each_entry_from(next, &encoder->bridge_chain, chain_node) {
> + if (next == iter)
> + break;
> +
> + if (next->funcs->pre_enable)
> + next->funcs->pre_enable(next);
> + }
> + }
> +
> if (iter->funcs->pre_enable)
> iter->funcs->pre_enable(iter);
>
> + if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST)
> + iter = limit;
> +
> if (iter == bridge)
> break;
> }
> @@ -667,6 +735,25 @@ void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
> }
> EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
>
> +static void drm_atomic_bridge_call_post_disable(struct drm_bridge *bridge,
> + struct drm_atomic_state *old_state)
> +{
> + if (bridge->funcs->atomic_post_disable) {
> + struct drm_bridge_state *old_bridge_state;
> +
> + old_bridge_state =
> + drm_atomic_get_old_bridge_state(old_state,
> + bridge);
> + if (WARN_ON(!old_bridge_state))
> + return;
> +
> + bridge->funcs->atomic_post_disable(bridge,
> + old_bridge_state);
> + } else if (bridge->funcs->post_disable) {
> + bridge->funcs->post_disable(bridge);
> + }
> +}
> +
> /**
> * drm_atomic_bridge_chain_post_disable - cleans up after disabling all bridges
> * in the encoder chain
> @@ -677,6 +764,9 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_disable);
> * &drm_bridge_funcs.post_disable) op for all the bridges in the encoder chain,
> * starting from the first bridge to the last. These are called after completing
> * &drm_encoder_helper_funcs.atomic_disable
> + * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the post_disable for
> + * that bridge will be called before the previous one to reverse the pre_enable
> + * calling direction.
> *
> * Note: the bridge passed should be the one closest to the encoder
> */
> @@ -684,30 +774,69 @@ void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
> struct drm_atomic_state *old_state)
> {
> struct drm_encoder *encoder;
> + struct drm_bridge *next, *limit;
>
> if (!bridge)
> return;
>
> encoder = bridge->encoder;
> +
> list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) {
> - if (bridge->funcs->atomic_post_disable) {
> - struct drm_bridge_state *old_bridge_state;
> + limit = NULL;
> +
> + if (!list_is_last(&bridge->chain_node, &encoder->bridge_chain)) {
> + next = list_next_entry(bridge, chain_node);
> +
> + if (next->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
> + limit = next;
> +
> + list_for_each_entry_from(next, &encoder->bridge_chain,
> + chain_node) {
> + if (!(next->ops &
> + DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
> + next = list_prev_entry(next, chain_node);
> + limit = next;
> + break;
> + }
> + }
> +
> + list_for_each_entry_from_reverse(next, &encoder->bridge_chain,
> + chain_node) {
> + if (next == bridge)
> + break;
> +
> + drm_atomic_bridge_call_post_disable(next,
> + old_state);
> + }
> + }
> + }
>
> - old_bridge_state =
> - drm_atomic_get_old_bridge_state(old_state,
> - bridge);
> - if (WARN_ON(!old_bridge_state))
> - return;
> + drm_atomic_bridge_call_post_disable(bridge, old_state);
>
> - bridge->funcs->atomic_post_disable(bridge,
> - old_bridge_state);
> - } else if (bridge->funcs->post_disable) {
> - bridge->funcs->post_disable(bridge);
> - }
> + if (limit)
> + bridge = limit;
> }
> }
> EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
>
> +static void drm_atomic_bridge_call_pre_enable(struct drm_bridge *bridge,
> + struct drm_atomic_state *old_state)
> +{
> + if (bridge->funcs->atomic_pre_enable) {
> + struct drm_bridge_state *old_bridge_state;
> +
> + old_bridge_state =
> + drm_atomic_get_old_bridge_state(old_state,
> + bridge);
> + if (WARN_ON(!old_bridge_state))
> + return;
> +
> + bridge->funcs->atomic_pre_enable(bridge, old_bridge_state);
> + } else if (bridge->funcs->pre_enable) {
> + bridge->funcs->pre_enable(bridge);
> + }
> +}
> +
> /**
> * drm_atomic_bridge_chain_pre_enable - prepares for enabling all bridges in
> * the encoder chain
> @@ -718,6 +847,8 @@ EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable);
> * &drm_bridge_funcs.pre_enable) 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_enable
> + * If a bridge sets the DRM_BRIDGE_OP_UPSTREAM_FIRST, then the pre_enable for
> + * the previous bridge will be called before pre_enable of this bridge.
> *
> * Note: the bridge passed should be the one closest to the encoder
> */
> @@ -725,26 +856,42 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
> struct drm_atomic_state *old_state)
> {
> struct drm_encoder *encoder;
> - struct drm_bridge *iter;
> + struct drm_bridge *iter, *next, *limit;
>
> if (!bridge)
> return;
>
> encoder = bridge->encoder;
> +
> list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
> - if (iter->funcs->atomic_pre_enable) {
> - struct drm_bridge_state *old_bridge_state;
> + if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST) {
> + next = iter;
> + limit = bridge;
> + list_for_each_entry_from_reverse(next,
> + &encoder->bridge_chain,
> + chain_node) {
> + if (next == bridge)
> + break;
> +
> + if (!(next->ops &
> + DRM_BRIDGE_OP_UPSTREAM_FIRST)) {
> + limit = list_prev_entry(next, chain_node);
> + break;
> + }
> + }
> +
> + list_for_each_entry_from(next, &encoder->bridge_chain, chain_node) {
> + if (next == iter)
> + break;
> +
> + drm_atomic_bridge_call_pre_enable(next, old_state);
> + }
> + }
This is hard to understand, I have trouble figuring out if it does the
right thing when multiple bridges set the DRM_BRIDGE_OP_UPSTREAM_FIRST
flag (or actually even when a single bridge does so). Comments would
help, but I wonder if it wouldn't be simpler to switch to a recursive
implementation.
It also seems that merging the legacy and atomic versions of the code
would be a good idea. They could both call into a shared implementation,
with the legacy version passing a NULL state, and the atomic op being
considered only if the state is not NULL.
>
> - old_bridge_state =
> - drm_atomic_get_old_bridge_state(old_state,
> - iter);
> - if (WARN_ON(!old_bridge_state))
> - return;
> + drm_atomic_bridge_call_pre_enable(iter, old_state);
>
> - iter->funcs->atomic_pre_enable(iter, old_bridge_state);
> - } else if (iter->funcs->pre_enable) {
> - iter->funcs->pre_enable(iter);
> - }
> + if (iter->ops & DRM_BRIDGE_OP_UPSTREAM_FIRST)
> + iter = limit;
>
> if (iter == bridge)
> break;
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index f27b4060faa2..523ec9d8f3f8 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -725,6 +725,14 @@ enum drm_bridge_ops {
> * this flag shall implement the &drm_bridge_funcs->get_modes callback.
> */
> DRM_BRIDGE_OP_MODES = BIT(3),
> + /**
> + * @DRM_BRIDGE_OP_UPSTREAM_FIRST: The bridge can requires
s/can //
> + * that the upstream node pre_enable is called before its pre_enable,
s/node/bridge/ ?
> + * and conversely for post_disables. This is most frequently a
s/post_disables/post_disable/
Bonus points if you use the correct markup to link to those operations.
> + * requirement for DSI devices which need the host to be initialised
> + * before them.
> + */
> + DRM_BRIDGE_OP_UPSTREAM_FIRST = BIT(4),
> };
>
> /**
--
Regards,
Laurent Pinchart
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