[PATCH 5/6] drm/i915: check for the supported strides on HSW+ FBC

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

I could only find the restrictions for HSW+, but I think it's safe to
assume that the older platforms also can't support the configurations
HSW can't support. The older platforms probably have additional
restrictions, so we need to figure out those and implement them later.
Let's not block HSW+ FBC based on missing information for the older
platforms.

This may fix kms_frontbuffer_tracking failures depending on your
monitor configuration.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  1 +
 drivers/gpu/drm/i915/intel_fbc.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 52d07fb..4a4b2a9 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -936,6 +936,7 @@ struct i915_fbc {
 		FBC_CHIP_DEFAULT, /* disabled by default on this chip */
 		FBC_ROTATION, /* rotation is not supported */
 		FBC_IN_DBG_MASTER, /* kernel debugger is active */
+		FBC_BAD_STRIDE, /* stride is not supported */
 	} no_fbc_reason;
 
 	bool (*fbc_enabled)(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 0a24e96..7b65b00 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -501,6 +501,8 @@ const char *intel_no_fbc_reason_str(enum no_fbc_reason reason)
 		return "rotation unsupported";
 	case FBC_IN_DBG_MASTER:
 		return "Kernel debugger is active";
+	case FBC_BAD_STRIDE:
+		return "framebuffer stride not supported";
 	default:
 		MISSING_CASE(reason);
 		return "unknown reason";
@@ -804,6 +806,14 @@ static void __intel_fbc_update(struct drm_i915_private *dev_priv)
 		goto out_disable;
 	}
 
+	/* TODO: we need to figure out what are the stride restrictions for the
+	 * older platforms. */
+	if (fb->pitches[0] < 512 || fb->pitches[0] > 16384 ||
+	    (fb->pitches[0] & (64 - 1)) != 0) {
+		set_no_fbc_reason(dev_priv, FBC_BAD_STRIDE);
+		goto out_disable;
+	}
+
 	/* If the kernel debugger is active, always disable compression */
 	if (in_dbg_master()) {
 		set_no_fbc_reason(dev_priv, FBC_IN_DBG_MASTER);
-- 
2.1.4

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