On Wed, 20 Dec 2017, Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> wrote:
> Occasionally there are LINK_ADDRESS sideband messages timing out with the
> Lenovo MST dock + Dell MST monitor(w/ in-built branch) setup I have. These
> failures lead to the display not coming up on boot. Power cycling the port
> corresponding to the MST monitor's branch device and resending the message
> fixes the issue. I am not entirely sure if this is specific to my setup.
> However, as the power state is toggled conditionally on LINK_ADDRESS
> timeouts, this should not affect the working cases.
With stuff like this, I always wonder if catering for a failing setup
blocks us from improving working setups, because once we add this, we
can't regress it. For example, is there a valid scenario where we'd want
to fail fast here, instead of retrying?
Some nits below.
> Cc: Lyude <lyude@xxxxxxxxxx>
> Cc: Dave Airlie <airlied@xxxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 70dcfa58d3c2..e06defcdcf18 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1596,8 +1596,9 @@ static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
> int len;
> struct drm_dp_sideband_msg_tx *txmsg;
> int ret;
> + int attempts = 5;
>
> - txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
> +retry: txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
> if (!txmsg)
> return;
>
> @@ -1635,9 +1636,17 @@ static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
> }
> (*mgr->cbs->hotplug)(mgr);
> }
> + } else if (attempts--) {
You'll end up doing (attempts + 1) attempts, including the first one.
> + kfree(txmsg);
How about memset(txmsg, 0, sizoef(*txmsg)); here and move the goto label
down to avoid repeated allocations?
> + drm_dp_send_power_updown_phy(mstb->mgr, mstb->port_parent,
> + false);
> + drm_dp_send_power_updown_phy(mstb->mgr, mstb->port_parent,
> + true);
> + DRM_DEBUG_KMS("link address failed %d, retrying\n", ret);
Maybe do the debug message before you power down/up?
BR,
Jani.
> + goto retry;
> } else {
> mstb->link_address_sent = false;
> - DRM_DEBUG_KMS("link address failed %d\n", ret);
> + DRM_DEBUG_KMS("link address failed %d, giving up\n", ret);
> }
>
> kfree(txmsg);
--
Jani Nikula, Intel Open Source Technology Center
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