drm/i915: pipe config quirk infrastructure plus sdvo mode.flags fix

For various reasons the hw state readout might not be able to
faithfully match the hw state:
- broken hw (like the case which motivated this patch here where the
  sdvo encoder does not implemented mandatory functionality
  correctly).
- platforms which are not supported fully with the pipe config
  infrastructure
- if our code doesn't support a given hw configuration natively, e.g.
  special restrictions on the per-pipe panel fitters when they're used
  in high-quality scaling modes.

In all these cases both fastboot and the hw state cross checker need
to be aware of these cases and act accordingly. To be able to do this
add a new quirk flag to the pipe config structure.

The specific case at hand is an sdvo encoder which doesn't implement
the get_timings function, so adjusted_mode flags will be wrong. The
strange thing though is that the encoder _does_ work, even though it
doesn't implement any of the timings functions (so neither get nor
set, neither for input nor output timings).

Not that non-compliant sdvo encoder are any surprise at all ...

v2:
- Don't read random garbage from the dtd if the get_timings call
  failed (suggested by Chris).
- Still check the interlaced flag, that's read out from someplace
  else. We want maximal paranoia, after all.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -8091,6 +8091,9 @@ intel_pipe_config_compare(struct drm_device *dev,
 		return false; \
 	}
 
+#define PIPE_CONF_QUIRK(quirk)	\
+	((current_config->quirks | pipe_config->quirks) & (quirk))
+
 	PIPE_CONF_CHECK_I(cpu_transcoder);
 
 	PIPE_CONF_CHECK_I(has_pch_encoder);
@@ -8121,6 +8124,7 @@ intel_pipe_config_compare(struct drm_device *dev,
 	PIPE_CONF_CHECK_FLAGS(adjusted_mode.flags,
 			      DRM_MODE_FLAG_INTERLACE);
 
+	if (!PIPE_CONF_QUIRK(PIPE_CONFIG_QUIRK_MODE_SYNC_FLAGS)) {
 		PIPE_CONF_CHECK_FLAGS(adjusted_mode.flags,
 				      DRM_MODE_FLAG_PHSYNC);
 		PIPE_CONF_CHECK_FLAGS(adjusted_mode.flags,
@@ -8129,6 +8133,7 @@ intel_pipe_config_compare(struct drm_device *dev,
 				      DRM_MODE_FLAG_PVSYNC);
 		PIPE_CONF_CHECK_FLAGS(adjusted_mode.flags,
 				      DRM_MODE_FLAG_NVSYNC);
+	}
 
 	PIPE_CONF_CHECK_I(requested_mode.hdisplay);
 	PIPE_CONF_CHECK_I(requested_mode.vdisplay);
@@ -8145,6 +8150,7 @@ intel_pipe_config_compare(struct drm_device *dev,
 
 #undef PIPE_CONF_CHECK_I
 #undef PIPE_CONF_CHECK_FLAGS
+#undef PIPE_CONF_QUIRK
 
 	return true;
 }

drivers/gpu/drm/i915/intel_drv.h

@@ -193,6 +193,17 @@ typedef struct dpll {
 } intel_clock_t;
 
 struct intel_crtc_config {
+	/**
+	 * quirks - bitfield with hw state readout quirks
+	 *
+	 * For various reasons the hw state readout code might not be able to
+	 * completely faithfully read out the current state. These cases are
+	 * tracked with quirk flags so that fastboot and state checker can act
+	 * accordingly.
+	 */
+#define PIPE_CONFIG_QUIRK_MODE_SYNC_FLAGS (1<<0) /* unreliable sync mode.flags */
+	unsigned long quirks;
+
 	struct drm_display_mode requested_mode;
 	struct drm_display_mode adjusted_mode;
 	/* This flag must be set by the encoder's compute_config callback if it

drivers/gpu/drm/i915/intel_sdvo.c

@@ -1324,10 +1324,11 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder,
 
 	ret = intel_sdvo_get_input_timing(intel_sdvo, &dtd);
 	if (!ret) {
+		/* Some sdvo encoders are not spec compliant and don't
+		 * implement the mandatory get_timings function. */
 		DRM_DEBUG_DRIVER("failed to retrieve SDVO DTD\n");
-		return;
-	}
-
+		pipe_config->quirks |= PIPE_CONFIG_QUIRK_MODE_SYNC_FLAGS;
+	} else {
 		if (dtd.part2.dtd_flags & DTD_FLAG_HSYNC_POSITIVE)
 			flags |= DRM_MODE_FLAG_PHSYNC;
 		else
@@ -1337,6 +1338,7 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder,
 			flags |= DRM_MODE_FLAG_PVSYNC;
 		else
 			flags |= DRM_MODE_FLAG_NVSYNC;
+	}
 
 	pipe_config->adjusted_mode.flags |= flags;