From e3bc91842bf186ec149c852f48993235ef7ad27f Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 3 Jul 2012 10:21:06 +0100
Subject: [PATCH] sna: Allow booting on older kernels by disabling HW
 acceleration

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 src/sna/kgem.c       | 16 +++++++++++++++-
 src/sna/sna_driver.c | 15 +--------------
 2 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/src/sna/kgem.c b/src/sna/kgem.c
index 76f6cae1..43fa7050 100644
--- a/src/sna/kgem.c
+++ b/src/sna/kgem.c
@@ -595,6 +595,20 @@ static bool __kgem_throttle(struct kgem *kgem)
 	return drmIoctl(kgem->fd, DRM_IOCTL_I915_GEM_THROTTLE, NULL) == -EIO;
 }
 
+static bool is_hw_supported(struct kgem *kgem)
+{
+	if (DBG_NO_HW)
+		return false;
+
+	if (kgem->gen >= 60) /* Only if the kernel supports the BLT ring */
+		return gem_param(kgem, I915_PARAM_HAS_BLT) > 0;
+
+	if (kgem->gen <= 20) /* dynamic GTT is fubar */
+		return false;
+
+	return true;
+}
+
 void kgem_init(struct kgem *kgem, int fd, struct pci_device *dev, int gen)
 {
 	struct drm_i915_gem_get_aperture aperture;
@@ -607,7 +621,7 @@ void kgem_init(struct kgem *kgem, int fd, struct pci_device *dev, int gen)
 	kgem->fd = fd;
 	kgem->gen = gen;
 	kgem->wedged = __kgem_throttle(kgem);
-	kgem->wedged |= DBG_NO_HW;
+	kgem->wedged |= !is_hw_supported(kgem);
 
 	kgem->batch_size = ARRAY_SIZE(kgem->batch);
 	if (gen == 22)
diff --git a/src/sna/sna_driver.c b/src/sna/sna_driver.c
index 047b8654..f7eeca58 100644
--- a/src/sna/sna_driver.c
+++ b/src/sna/sna_driver.c
@@ -294,8 +294,7 @@ static int sna_open_drm_master(ScrnInfoPtr scrn)
 	struct sna *sna = to_sna(scrn);
 	struct pci_device *pci = sna->PciInfo;
 	drmSetVersion sv;
-	struct drm_i915_getparam gp;
-	int err, val;
+	int err;
 	char busid[20];
 	int fd;
 
@@ -335,18 +334,6 @@ static int sna_open_drm_master(ScrnInfoPtr scrn)
 		return -1;
 	}
 
-	val = FALSE;
-
-	VG_CLEAR(gp);
-	gp.param = I915_PARAM_HAS_BLT;
-	gp.value = &val;
-	if (drmIoctl(fd, DRM_IOCTL_I915_GETPARAM, &gp)) {
-		xf86DrvMsg(scrn->scrnIndex, X_ERROR,
-			   "Failed to detect BLT.  Kernel 2.6.37 required.\n");
-		drmClose(fd);
-		return -1;
-	}
-
 	dev = malloc(sizeof(*dev));
 	if (dev) {
 		int flags;