Re: [PATCH 4/6] drm/dp: Introduce DP MST topology manager state to track DP link bw

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On Wed, 2017-01-04 at 10:33 +0100, Daniel Vetter wrote:
> On Tue, Jan 03, 2017 at 01:01:49PM -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 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@xxxxxxxxx>
> 
> Overall issue with the patch is that dp helpers now have 2 places where
> available_slots is stored: One for atomic drivers in ->state, and the
> legacy one. I think it'd be good to rework the legacy codepaths (i.e.
> drm_dp_find_vcpi_slots) to use mgr->state->avail_slots, and remove
> mgr->avail_slots entirely.

PATCH 2/6 does that. mgr->avail_slots is not updated in the legacy code
path, so the check turns out to be against mgr->total_slots. So, I did
just that, albeit explicitly. 

-DK

> 
> Another design concern below, but in principle this looks like what we
> need.
> -Daniel
> 
> 
> > ---
> >  drivers/gpu/drm/drm_atomic.c          | 66 +++++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/drm_atomic_helper.c   | 10 ++++++
> >  drivers/gpu/drm/drm_dp_mst_topology.c | 10 ++++++
> >  include/drm/drm_atomic.h              | 13 +++++++
> >  include/drm/drm_dp_mst_helper.h       | 13 +++++++
> >  5 files changed, 112 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 681d5f9..b8e2cea 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -31,6 +31,7 @@
> >  #include <drm/drm_mode.h>
> >  #include <drm/drm_plane_helper.h>
> >  #include <drm/drm_print.h>
> > +#include <drm/drm_dp_mst_helper.h>
> >  #include <linux/sync_file.h>
> >  
> >  #include "drm_crtc_internal.h"
> > @@ -62,6 +63,7 @@ void drm_atomic_state_default_release(struct drm_atomic_state *state)
> >  	kfree(state->connectors);
> >  	kfree(state->crtcs);
> >  	kfree(state->planes);
> > +	kfree(state->dp_mst_topologies);
> >  }
> >  EXPORT_SYMBOL(drm_atomic_state_default_release);
> >  
> > @@ -189,6 +191,18 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state)
> >  		state->planes[i].ptr = NULL;
> >  		state->planes[i].state = NULL;
> >  	}
> > +
> > +	for (i = 0; i < state->num_mst_topologies; i++) {
> > +		struct drm_dp_mst_topology_mgr *mgr = state->dp_mst_topologies[i].ptr;
> > +
> > +		if (!mgr)
> > +			continue;
> > +
> > +		kfree(state->dp_mst_topologies[i].state);
> > +		state->dp_mst_topologies[i].ptr = NULL;
> > +		state->dp_mst_topologies[i].state = NULL;
> > +	}
> > +
> >  }
> >  EXPORT_SYMBOL(drm_atomic_state_default_clear);
> >  
> > @@ -981,6 +995,58 @@ static void drm_atomic_plane_print_state(struct drm_printer *p,
> >  		plane->funcs->atomic_print_state(p, state);
> >  }
> >  
> > +struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
> > +		struct drm_dp_mst_topology_mgr *mgr)
> > +{
> > +
> > +	int ret, i;
> > +	size_t new_size;
> > +	struct __drm_dp_mst_topology_state *new_arr;
> > +	struct drm_dp_mst_topology_state *new_mst_state;
> > +	int num_topologies;
> > +	struct drm_mode_config *config = &mgr->dev->mode_config;
> > +
> > +	WARN_ON(!state->acquire_ctx);
> > +
> > +	ret = drm_modeset_lock(&config->connection_mutex, state->acquire_ctx);
> > +	if (ret)
> > +		return ERR_PTR(ret);
> > +
> > +	for (i = 0; i < state->num_mst_topologies; i++) {
> > +		if (mgr == state->dp_mst_topologies[i].ptr &&
> > +		    state->dp_mst_topologies[i].state) {
> > +			return state->dp_mst_topologies[i].state;
> > +		}
> > +	}
> > +
> > +	num_topologies = state->num_mst_topologies + 1;
> > +	new_size = sizeof(*state->dp_mst_topologies) * num_topologies;
> > +	new_arr = krealloc(state->dp_mst_topologies, new_size, GFP_KERNEL);
> > +	if (!new_arr)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	state->dp_mst_topologies = new_arr;
> > +	memset(&state->dp_mst_topologies[state->num_mst_topologies], 0,
> > +		sizeof(*state->dp_mst_topologies));
> > +
> > +	new_mst_state = kmalloc(sizeof(*mgr->state), GFP_KERNEL);
> > +	if (!new_mst_state)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	new_mst_state->avail_slots = mgr->state->avail_slots;
> > +	state->dp_mst_topologies[state->num_mst_topologies].state = new_mst_state;
> > +	state->dp_mst_topologies[state->num_mst_topologies].ptr = mgr;
> > +	state->num_mst_topologies = num_topologies;
> > +	new_mst_state->mgr = mgr;
> > +	mgr->state->state = state;
> > +
> > +	DRM_DEBUG_ATOMIC("Added [MST Topology w/ base connector:%d] %p state to %p\n",
> > +			 mgr->conn_base_id, new_mst_state, state);
> > +
> > +	return new_mst_state;
> > +}
> > +EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);
> > +
> >  /**
> >   * drm_atomic_get_connector_state - get connector state
> >   * @state: global atomic state object
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index 5e52244..1cd38b7 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -30,6 +30,7 @@
> >  #include <drm/drm_plane_helper.h>
> >  #include <drm/drm_crtc_helper.h>
> >  #include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_dp_mst_helper.h>
> >  #include <linux/dma-fence.h>
> >  
> >  #include "drm_crtc_internal.h"
> > @@ -1992,6 +1993,15 @@ void drm_atomic_helper_swap_state(struct drm_atomic_state *state,
> >  		connector->state->state = NULL;
> >  	}
> >  
> > +	for (i = 0; i < state->num_mst_topologies; i++) {
> > +		struct drm_dp_mst_topology_mgr *mgr;
> > +
> > +		mgr = state->dp_mst_topologies[i].ptr;
> > +		mgr->state->state = state;
> > +		swap(state->dp_mst_topologies[i].state, mgr->state);
> > +		mgr->state->state = NULL;
> > +	}
> 
> I'm not sure we want to tie the dp mst helpers that closely with the
> atomic machinery, otoh it makes things a lot easier. My concern is that
> drm_atomic_state is a core structure, whereas the dp_mst stuff is a
> helper, which means we have a control inversion here compared to the
> normal pattern.
> 
> > +
> >  	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> >  		crtc->state->state = state;
> >  		swap(state->crtcs[i].state, crtc->state);
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index d42a6c0..1be19e1 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -2042,6 +2042,9 @@ 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;
> > +
> >  		/* add initial branch device at LCT 1 */
> >  		mstb = drm_dp_add_mst_branch_device(1, NULL);
> >  		if (mstb == NULL) {
> > @@ -2973,6 +2976,11 @@ int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
> >  	mgr->proposed_vcpis = kcalloc(max_payloads, sizeof(struct drm_dp_vcpi *), GFP_KERNEL);
> >  	if (!mgr->proposed_vcpis)
> >  		return -ENOMEM;
> > +	mgr->state = kzalloc(sizeof(*mgr->state), GFP_KERNEL);
> > +	if (!mgr->state)
> > +		return -ENOMEM;
> > +	mgr->state->mgr = mgr;
> > +
> >  	set_bit(0, &mgr->payload_mask);
> >  	if (test_calc_pbn_mode() < 0)
> >  		DRM_ERROR("MST PBN self-test failed\n");
> > @@ -2995,6 +3003,8 @@ void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
> >  	kfree(mgr->proposed_vcpis);
> >  	mgr->proposed_vcpis = NULL;
> >  	mutex_unlock(&mgr->payload_lock);
> > +	kfree(mgr->state);
> > +	mgr->state = NULL;
> >  	mgr->dev = NULL;
> >  	mgr->aux = NULL;
> >  }
> > diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> > index fd2d971..7ac5ed6 100644
> > --- a/include/drm/drm_atomic.h
> > +++ b/include/drm/drm_atomic.h
> > @@ -153,6 +153,11 @@ struct __drm_connnectors_state {
> >  	struct drm_connector_state *state;
> >  };
> >  
> > +struct __drm_dp_mst_topology_state {
> > +	struct drm_dp_mst_topology_mgr *ptr;
> > +	struct drm_dp_mst_topology_state *state;
> 
> One way to fix that control inversion I mentioned above is to use void*
> pionters here, and then have callbacks for atomic_destroy and swap_state
> on top. A bit more shuffling, but we could then use that for other driver
> private objects.
> 
> Other option is to stuff it into intel_atomic_state.
> 
> > +};
> > +
> >  /**
> >   * struct drm_atomic_state - the global state object for atomic updates
> >   * @ref: count of all references to this state (will not be freed until zero)
> > @@ -164,6 +169,8 @@ struct __drm_connnectors_state {
> >   * @crtcs: pointer to array of CRTC pointers
> >   * @num_connector: size of the @connectors and @connector_states arrays
> >   * @connectors: pointer to array of structures with per-connector data
> > + * @num_mst_topologies: size of the @dp_mst_topologies array
> > + * @dp_mst_topologies: pointer to array of structures with per-MST topology manager data
> >   * @acquire_ctx: acquire context for this atomic modeset state update
> >   */
> >  struct drm_atomic_state {
> > @@ -177,6 +184,8 @@ struct drm_atomic_state {
> >  	struct __drm_crtcs_state *crtcs;
> >  	int num_connector;
> >  	struct __drm_connnectors_state *connectors;
> > +	int num_mst_topologies;
> > +	struct __drm_dp_mst_topology_state *dp_mst_topologies;
> >  
> >  	struct drm_modeset_acquire_ctx *acquire_ctx;
> >  
> > @@ -250,6 +259,10 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> >  		struct drm_connector_state *state, struct drm_property *property,
> >  		uint64_t val);
> >  
> > +struct drm_dp_mst_topology_state * __must_check
> > +drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
> > +				  struct drm_dp_mst_topology_mgr *mgr);
> > +
> >  /**
> >   * drm_atomic_get_existing_crtc_state - get crtc state, if it exists
> >   * @state: global atomic state object
> > diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
> > index 98d3c73..0a9bf20 100644
> > --- a/include/drm/drm_dp_mst_helper.h
> > +++ b/include/drm/drm_dp_mst_helper.h
> > @@ -403,6 +403,12 @@ 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 +487,11 @@ struct drm_dp_mst_topology_mgr {
> >  	int pbn_div;
> >  
> >  	/**
> > +	 *  @state: MST topology manager state for atomic modesetting drivers
> > +	 */
> > +	struct drm_dp_mst_topology_state *state;
> > +
> > +	/**
> >  	 * @qlock: protects @tx_msg_downq, the tx_slots in struct
> >  	 * &drm_dp_mst_branch and txmsg->state once they are queued
> >  	 */
> > @@ -596,4 +607,6 @@ 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
> > 
> 

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