Re: [PATCH 4/5] drm_dp_cec: add plumbing in preparation for MST support

From: Sam McNally
Date: Wed Sep 09 2020 - 03:04:45 EST

On Tue, 8 Sep 2020 at 18:41, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
>
> On 01/09/2020 08:22, Sam McNally wrote:
> > From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> >
> > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> > [sammc@xxxxxxxxxxxx:
> > - rebased
> > - removed polling-related changes
> > - moved the calls to drm_dp_cec_(un)set_edid() into the next patch
> > ]
> > Signed-off-by: Sam McNally <sammc@xxxxxxxxxxxx>
> > ---
> >
> > .../display/amdgpu_dm/amdgpu_dm_mst_types.c | 2 +-
> > drivers/gpu/drm/drm_dp_cec.c | 22 ++++++++++---------
> > drivers/gpu/drm/i915/display/intel_dp.c | 2 +-
> > drivers/gpu/drm/nouveau/nouveau_connector.c | 2 +-
> > include/drm/drm_dp_helper.h | 6 +++--
> > 5 files changed, 19 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > index 461fa4da0a34..6e7075893ec9 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > @@ -419,7 +419,7 @@ void amdgpu_dm_initialize_dp_connector(struct amdgpu_display_manager *dm,
> >
> > drm_dp_aux_init(&aconnector->dm_dp_aux.aux);
> > drm_dp_cec_register_connector(&aconnector->dm_dp_aux.aux,
> > - &aconnector->base);
> > + &aconnector->base, false);
> >
> > if (aconnector->base.connector_type == DRM_MODE_CONNECTOR_eDP)
> > return;
> > diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
> > index 3ab2609f9ec7..04ab7b88055c 100644
> > --- a/drivers/gpu/drm/drm_dp_cec.c
> > +++ b/drivers/gpu/drm/drm_dp_cec.c
> > @@ -14,6 +14,7 @@
> > #include <drm/drm_connector.h>
> > #include <drm/drm_device.h>
> > #include <drm/drm_dp_helper.h>
> > +#include <drm/drm_dp_mst_helper.h>
> >
> > /*
> > * Unfortunately it turns out that we have a chicken-and-egg situation
> > @@ -338,8 +339,6 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid)
> > if (aux->cec.adap) {
> > if (aux->cec.adap->capabilities == cec_caps &&
> > aux->cec.adap->available_log_addrs == num_las) {
> > - /* Unchanged, so just set the phys addr */
> > - cec_s_phys_addr_from_edid(aux->cec.adap, edid);
> > goto unlock;
> > }
> > /*
> > @@ -364,15 +363,16 @@ void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid)
> > if (cec_register_adapter(aux->cec.adap, connector->dev->dev)) {
> > cec_delete_adapter(aux->cec.adap);
> > aux->cec.adap = NULL;
> > - } else {
> > - /*
> > - * Update the phys addr for the new CEC adapter. When called
> > - * from drm_dp_cec_register_connector() edid == NULL, so in
> > - * that case the phys addr is just invalidated.
> > - */
> > - cec_s_phys_addr_from_edid(aux->cec.adap, edid);
> > }
> > unlock:
> > + /*
> > + * Update the phys addr for the new CEC adapter. When called
> > + * from drm_dp_cec_register_connector() edid == NULL, so in
> > + * that case the phys addr is just invalidated.
> > + */
>
> The comment is no longer in sync with the code: if EDID == NULL, then
> nothing is done due to the edid check in the 'if' below.
>
> > + if (aux->cec.adap && edid) {
>
> I think this should just be: if (aux->cec.adap)
>
> Also, the {} aren't necessary here.
>
> > + cec_s_phys_addr_from_edid(aux->cec.adap, edid);
> > + }
> > mutex_unlock(&aux->cec.lock);
> > }
> > EXPORT_SYMBOL(drm_dp_cec_set_edid);
>
> Frankly, the changes to this function should be dropped completely, from
> what I can see they are not necessary. It was done in my original patch
> because of the way I handled mst, but you did it differently (and I think
> better), so these changes are no longer needed.
>
> I know I am actually commenting on my old patch, but that patch was from a
> work-in-progress git branch and was never meant as a 'proper' patch.
>
> However, what complicates matters is that after digging a bit more I discovered
> that commit 732300154980 ("drm: Do not call drm_dp_cec_set_edid() while registering
> DP connectors") changed drm_dp_cec_register_connector() so that it no longer
> calls drm_dp_cec_set_edid(), but the comments there and in this function were
> not updated. It would be nice if you can add a patch fixing these outdated
> comments.
>
> Regardless of that change in commit 732300154980, the edid pointer can still be
> NULL and the existing behavior should be kept (i.e. create a CEC device, but with
> an invalid physical address since there is no EDID for some reason).
>
> Regards,
>
> Hans
>

Thanks. Leaving drm_dp_cec_set_edid() unchanged combined with Lyude's
suggestion to use aux->is_remote removes the need for this patch
entirely.

> > @@ -418,6 +418,7 @@ EXPORT_SYMBOL(drm_dp_cec_unset_edid);
> > * drm_dp_cec_register_connector() - register a new connector
> > * @aux: DisplayPort AUX channel
> > * @connector: drm connector
> > + * @is_mst: set to true if this is an MST branch
> > *
> > * A new connector was registered with associated CEC adapter name and
> > * CEC adapter parent device. After registering the name and parent
> > @@ -425,12 +426,13 @@ EXPORT_SYMBOL(drm_dp_cec_unset_edid);
> > * CEC and to register a CEC adapter if that is the case.
> > */
> > void drm_dp_cec_register_connector(struct drm_dp_aux *aux,
> > - struct drm_connector *connector)
> > + struct drm_connector *connector, bool is_mst)
> > {
> > WARN_ON(aux->cec.adap);
> > if (WARN_ON(!aux->transfer))
> > return;
> > aux->cec.connector = connector;
> > + aux->cec.is_mst = is_mst;
> > INIT_DELAYED_WORK(&aux->cec.unregister_work,
> > drm_dp_cec_unregister_work);
> > }
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 82b9de274f65..744cb55572f9 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -6261,7 +6261,7 @@ intel_dp_connector_register(struct drm_connector *connector)
> > intel_dp->aux.dev = connector->kdev;
> > ret = drm_dp_aux_register(&intel_dp->aux);
> > if (!ret)
> > - drm_dp_cec_register_connector(&intel_dp->aux, connector);
> > + drm_dp_cec_register_connector(&intel_dp->aux, connector, false);
> > return ret;
> > }
> >
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c
> > index 49dd0cbc332f..671a70e95cd1 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_connector.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
> > @@ -1414,7 +1414,7 @@ nouveau_connector_create(struct drm_device *dev,
> > switch (type) {
> > case DRM_MODE_CONNECTOR_DisplayPort:
> > case DRM_MODE_CONNECTOR_eDP:
> > - drm_dp_cec_register_connector(&nv_connector->aux, connector);
> > + drm_dp_cec_register_connector(&nv_connector->aux, connector, false);
> > break;
> > }
> >
> > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> > index 85513eeb2196..12bca1b9512b 100644
> > --- a/include/drm/drm_dp_helper.h
> > +++ b/include/drm/drm_dp_helper.h
> > @@ -1495,12 +1495,14 @@ struct drm_connector;
> > * @lock: mutex protecting this struct
> > * @adap: the CEC adapter for CEC-Tunneling-over-AUX support.
> > * @connector: the connector this CEC adapter is associated with
> > + * @is_mst: this is an MST branch
> > * @unregister_work: unregister the CEC adapter
> > */
> > struct drm_dp_aux_cec {
> > struct mutex lock;
> > struct cec_adapter *adap;
> > struct drm_connector *connector;
> > + bool is_mst;
> > struct delayed_work unregister_work;
> > };
> >
> > @@ -1746,7 +1748,7 @@ drm_dp_has_quirk(const struct drm_dp_desc *desc, u32 edid_quirks,
> > #ifdef CONFIG_DRM_DP_CEC
> > void drm_dp_cec_irq(struct drm_dp_aux *aux);
> > void drm_dp_cec_register_connector(struct drm_dp_aux *aux,
> > - struct drm_connector *connector);
> > + struct drm_connector *connector, bool is_mst);
> > void drm_dp_cec_unregister_connector(struct drm_dp_aux *aux);
> > void drm_dp_cec_set_edid(struct drm_dp_aux *aux, const struct edid *edid);
> > void drm_dp_cec_unset_edid(struct drm_dp_aux *aux);
> > @@ -1757,7 +1759,7 @@ static inline void drm_dp_cec_irq(struct drm_dp_aux *aux)
> >
> > static inline void
> > drm_dp_cec_register_connector(struct drm_dp_aux *aux,
> > - struct drm_connector *connector)
> > + struct drm_connector *connector, bool is_mst)
> > {
> > }
> >
> >
>