[PATCH v2 5/9] drm/dp: Introduce MST topology state

[Daniel Vetter]

On Tue, Jan 24, 2017 at 03:49:33PM -0800, Dhinakaran Pandiyan wrote:
> Link bandwidth is shared between multiple display streams in DP MST
> configurations. The DP MST topology manager structure maintains the
> shared link bandwidth for a primary link directly connected to the GPU. For
> atomic modesetting drivers, checking if there is sufficient link bandwidth
> for a mode needs to be done during the atomic_check phase to avoid failed
> modesets. Let's encsapsulate the available link bw information in a
> private state structure so that bw can be allocated and released atomically
> for each of the ports sharing the primary link.
> 
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>

Yeah, I like how this neatly hides all the atomic state tracking now, and
just leaves the mst specific logic in the mst helpers.

> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 60 +++++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_mst_helper.h       | 20 ++++++++++++
>  2 files changed, 80 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index b871d4e..247286b 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -2042,6 +2042,8 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
>  			goto out_unlock;
>  		}
>  
> +		/* max. time slots - one slot for MTP header */
> +		mgr->state->avail_slots = 63;

We can't reset atomic state on each hotplug, that would wreak the atomic
tracking. E.g. there might still be a pipe around running on this output,
and then we'd go above 63 slots when we release that one. You need to init
this once in drm_dp_mst_topology_mgr_init() and then make sure it's always
accurate.

>  		/* add initial branch device at LCT 1 */
>  		mstb = drm_dp_add_mst_branch_device(1, NULL);
>  		if (mstb == NULL) {
> @@ -2935,6 +2937,55 @@ static void drm_dp_destroy_connector_work(struct work_struct *work)
>  		(*mgr->cbs->hotplug)(mgr);
>  }
>  
> +void drm_dp_mst_destroy_state(void *obj_state)
> +{
> +	kfree(obj_state);
> +}
> +
> +void drm_dp_mst_swap_state(void *obj, void **obj_state_ptr)
> +{
> +	struct drm_dp_mst_topology_mgr *mgr = obj;
> +	struct drm_dp_mst_topology_state **topology_state_ptr;
> +
> +	topology_state_ptr = (struct drm_dp_mst_topology_state **)obj_state_ptr;
> +
> +	mgr->state->state = (*topology_state_ptr)->state;
> +	swap(*topology_state_ptr, mgr->state);
> +	mgr->state->state = NULL;
> +}
> +
> +void *drm_dp_mst_duplicate_state(struct drm_atomic_state *state, void *obj)
> +{
> +	struct drm_dp_mst_topology_mgr *mgr = obj;
> +	struct drm_dp_mst_topology_state *new_mst_state;
> +
> +	if (WARN_ON(!mgr->state))
> +		return NULL;
> +
> +	new_mst_state = kmalloc(sizeof(*new_mst_state), GFP_KERNEL);
> +	if (new_mst_state) {
> +		new_mst_state->avail_slots = mgr->state->avail_slots;
> +		new_mst_state->mgr = mgr;
> +		new_mst_state->state = state;
> +	}

kmemdup is less code :-)

> +
> +	return new_mst_state;
> +}
> +
> +static const struct drm_private_state_funcs mst_state_funcs = {
> +	.swap_state = drm_dp_mst_swap_state,
> +	.destroy_state = drm_dp_mst_destroy_state,
> +	.duplicate_state = drm_dp_mst_duplicate_state,
> +};
> +

Needs a few lines of kernel-doc here since it's an exported function.

Cheers, Daniel

> +struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
> +								    struct drm_dp_mst_topology_mgr *mgr)
> +{
> +		return drm_atomic_get_priv_obj_state(state, mgr,
> +						     &mst_state_funcs);
> +}
> +EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);
> +
>  /**
>   * drm_dp_mst_topology_mgr_init - initialise a topology manager
>   * @mgr: manager struct to initialise
> @@ -2979,6 +3030,12 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
>  	if (test_calc_pbn_mode() < 0)
>  		DRM_ERROR("MST PBN self-test failed\n");
>  
> +	mgr->state = kzalloc(sizeof(*mgr->state), GFP_KERNEL);
> +	if (mgr->state == NULL)
> +		return -ENOMEM;
> +	mgr->state->mgr = mgr;
> +	mgr->funcs = &mst_state_funcs;
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL(drm_dp_mst_topology_mgr_init);
> @@ -2999,6 +3056,9 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
>  	mutex_unlock(&mgr->payload_lock);
>  	mgr->dev = NULL;
>  	mgr->aux = NULL;
> +	kfree(mgr->state);
> +	mgr->state = NULL;
> +	mgr->funcs = NULL;
>  }
>  EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);
>  
> diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
> index 98d3c73..8cbdbfa 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -24,6 +24,7 @@
>  
>  #include <linux/types.h>
>  #include <drm/drm_dp_helper.h>
> +#include <drm/drm_atomic.h>
>  
>  struct drm_dp_mst_branch;
>  
> @@ -403,6 +404,12 @@ struct drm_dp_payload {
>  	int vcpi;
>  };
>  
> +struct drm_dp_mst_topology_state {
> +	int avail_slots;
> +	struct drm_atomic_state *state;
> +	struct drm_dp_mst_topology_mgr *mgr;
> +};
> +
>  /**
>   * struct drm_dp_mst_topology_mgr - DisplayPort MST manager
>   *
> @@ -481,6 +488,16 @@ struct drm_dp_mst_topology_mgr {
>  	int pbn_div;
>  
>  	/**
> +	 * @state: State information for topology manager
> +	 */
> +	struct drm_dp_mst_topology_state *state;
> +
> +	/**
> +	 * @funcs: Atomic helper callbacks
> +	 */
> +	const struct drm_private_state_funcs *funcs;
> +
> +	/**
>  	 * @qlock: protects @tx_msg_downq, the tx_slots in struct
>  	 * &drm_dp_mst_branch and txmsg->state once they are queued
>  	 */
> @@ -596,4 +613,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
>  
>  void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr);
>  int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr);
> +struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
> +								    struct drm_dp_mst_topology_mgr *mgr);
> +
>  #endif
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch