drm/i915: Sanitize watermarks after hardware state readout (v4)
Although we can do a good job of reading out hardware state, the
graphics firmware may have programmed the watermarks in a creative way
that doesn't match how i915 would have chosen to program them. We
shouldn't trust the firmware's watermark programming, but should rather
re-calculate how we think WM's should be programmed and then shove those
values into the hardware.
We can do this pretty easily by creating a dummy top-level state,
running it through the check process to calculate all the values, and
then just programming the watermarks for each CRTC.
v2: Move watermark sanitization after our BIOS fb reconstruction; the
watermark calculations that we do here need to look at pstate->fb,
which isn't setup yet in intel_modeset_setup_hw_state(), even
though we have an enabled & visible plane.
v3:
- Don't move 'active = optimal' watermark assignment; we just undo
that change in the next patch anyway. (Ville)
- Move atomic helper locking fix to separate patch. (Maarten)
v4:
- Grab connection_mutex before calling atomic helper to duplicate
state. The connector loop inside the helper will throw a WARN
if we don't hold something to protect the connector list (and the
helper itself doesn't try to lock the list).
- Make failure to calculate watermarks for inherited state a WARN()
since it probably indicates a serious problem in either our state
readout code or our watermark code for this platform.
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index c1a3969..043adfa 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15276,6 +15276,78 @@
intel_enable_gt_powersave(dev);
}
+/*
+ * Calculate what we think the watermarks should be for the state we've read
+ * out of the hardware and then immediately program those watermarks so that
+ * we ensure the hardware settings match our internal state.
+ *
+ * We can calculate what we think WM's should be by creating a duplicate of the
+ * current state (which was constructed during hardware readout) and running it
+ * through the atomic check code to calculate new watermark values in the
+ * state object.
+ */
+static void sanitize_watermarks(struct drm_device *dev)
+{
+ struct drm_i915_private *dev_priv = to_i915(dev);
+ struct drm_atomic_state *state;
+ struct drm_crtc *crtc;
+ struct drm_crtc_state *cstate;
+ struct drm_modeset_acquire_ctx ctx;
+ int ret;
+ int i;
+
+ /* Only supported on platforms that use atomic watermark design */
+ if (!dev_priv->display.program_watermarks)
+ return;
+
+ /*
+ * We need to hold connection_mutex before calling duplicate_state so
+ * that the connector loop is protected.
+ */
+ drm_modeset_acquire_init(&ctx, 0);
+retry:
+ ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
+ if (ret == -EDEADLK) {
+ drm_modeset_backoff(&ctx);
+ goto retry;
+ } else if (WARN_ON(ret)) {
+ return;
+ }
+
+ state = drm_atomic_helper_duplicate_state(dev, &ctx);
+ if (WARN_ON(IS_ERR(state)))
+ return;
+
+ ret = intel_atomic_check(dev, state);
+ if (ret) {
+ /*
+ * If we fail here, it means that the hardware appears to be
+ * programmed in a way that shouldn't be possible, given our
+ * understanding of watermark requirements. This might mean a
+ * mistake in the hardware readout code or a mistake in the
+ * watermark calculations for a given platform. Raise a WARN
+ * so that this is noticeable.
+ *
+ * If this actually happens, we'll have to just leave the
+ * BIOS-programmed watermarks untouched and hope for the best.
+ */
+ WARN(true, "Could not determine valid watermarks for inherited state\n");
+ return;
+ }
+
+ /* Write calculated watermark values back */
+ to_i915(dev)->wm.config = to_intel_atomic_state(state)->wm_config;
+ for_each_crtc_in_state(state, crtc, cstate, i) {
+ struct intel_crtc_state *cs = to_intel_crtc_state(cstate);
+
+ dev_priv->display.program_watermarks(cs);
+ }
+
+ drm_atomic_state_free(state);
+ drm_modeset_drop_locks(&ctx);
+ drm_modeset_acquire_fini(&ctx);
+}
+
void intel_modeset_init(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
@@ -15396,6 +15468,13 @@
*/
intel_find_initial_plane_obj(crtc, &plane_config);
}
+
+ /*
+ * Make sure hardware watermarks really match the state we read out.
+ * Note that we need to do this after reconstructing the BIOS fb's
+ * since the watermark calculation done here will use pstate->fb.
+ */
+ sanitize_watermarks(dev);
}
static void intel_enable_pipe_a(struct drm_device *dev)