[PATCH 3/4] drm/dp/mst: Clear port->pdt when tearing down the i2c adapter

[Daniel Vetter]

On Wed, Oct 26, 2016 at 12:05:54PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The i2c adapter is only relevant for some peer device types, so
> let's clear the pdt if it's still the same as the old_pdt when we
> tear down the i2c adapter.
> 
> I don't really like this design pattern of updating port->whatever
> before doing the accompanying changes and passing around old_whatever
> to figure stuff out. Would make much more sense to me to the pass the
> new value around and only update the port->whatever when things are
> consistent. But let's try to work with what we have right now.
> 
> Cc: stable at vger.kernel.org
> Cc: Carlos Santa <carlos.santa at intel.com>
> Cc: Kirill A. Shutemov <kirill at shutemov.name>
> Tested-by: Carlos Santa <carlos.santa at intel.com>
> Tested-by: Kirill A. Shutemov <kirill at shutemov.name>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97666
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 04e457117980..956babc161e5 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -882,6 +882,9 @@ static void drm_dp_port_teardown_pdt(struct drm_dp_mst_port *port, int old_pdt)
>  		drm_dp_put_mst_branch_device(mstb);
>  		break;
>  	}
> +
> +	if (port->pdt == old_pdt)
> +		port->pdt = DP_PEER_DEVICE_NONE;

So from my understanding this is needed for the callsite in
drm_dp_destroy_connector_work(). All others are either the final destroy
path, or set up the ->pdt to something before calling this function. Only
this call site passes port->pdt. I think we should instead change this
callsite to set the port->pdt to NONE after the call, i.e.


diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 04e457117980..36f47092c703 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2919,6 +2919,7 @@ static void drm_dp_destroy_connector_work(struct work_struct *work)
 		mgr->cbs->destroy_connector(mgr, port->connector);
 
 		drm_dp_port_teardown_pdt(port, port->pdt);
+		port->pdt = DP_PEER_DEVICE_NONE;
 
 		if (!port->input && port->vcpi.vcpi > 0) {
 			drm_dp_mst_reset_vcpi_slots(mgr, port);


I think that would be more consistent than spreading the control flow even
more like in your patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch