Quoting Manasi Navare (2018-12-06 00:54:07)
> DSC can be supported per DP connector. This patch adds a per connector
> debugfs node to expose DSC support capability by the kernel.
> The same node can be used from userspace to force DSC enable.
So this has a nice deadlock that is killing icl sporadically...
> +static int i915_dsc_fec_support_show(struct seq_file *m, void *data)
> +{
> + struct drm_connector *connector = m->private;
> + struct drm_device *dev = connector->dev;
> + struct drm_crtc *crtc;
> + struct intel_dp *intel_dp;
> + struct drm_modeset_acquire_ctx ctx;
> + struct intel_crtc_state *crtc_state = NULL;
> + int ret = 0;
> + bool try_again = false;
> +
> + drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE);
> +
> + do {
> + ret = drm_modeset_lock(&dev->mode_config.connection_mutex,
> + &ctx);
> + if (ret) {
> + ret = -EINTR;
> + break;
> + }
> + crtc = connector->state->crtc;
> + if (connector->status != connector_status_connected || !crtc) {
> + ret = -ENODEV;
> + break;
> + }
> + ret = drm_modeset_lock(&crtc->mutex, &ctx);
> + if (ret == -EDEADLK) {
> + ret = drm_modeset_backoff(&ctx);
> + if (!ret) {
> + try_again = true;
try_again is never cleared on the next loop, so after you hit the
backoff, we never escape on success.
Reported-by: Tomi Sarvela <tomi.p.sarvela@xxxxxxxxx>
-Chris
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