radeon: Default to leaving AGP transfer mode and fast writes unchanged.

Based on the assumption that firmware should have set up the card and host
bridge appropriately for these settings, this may actually be safer, at least
for the transfer rate; leaving fast writes enabled is hopefully safe as well,
it certainly is on my sytem.

See https://bugs.freedesktop.org/show_bug.cgi?id=9284 .

1 files changed, 52 insertions, 15 deletions

diff --git a/src/radeon_dri.c b/src/radeon_dri.c
index e2238252..35e41545 100644
--- a/src/radeon_dri.c
+++ b/src/radeon_dri.c
@@ -723,10 +723,60 @@ static Bool RADEONSetAgpMode(RADEONInfoPtr info, ScreenPtr pScreen)
     unsigned long mode   = drmAgpGetMode(info->drmFD);	/* Default mode */
     unsigned int  vendor = drmAgpVendorId(info->drmFD);
     unsigned int  device = drmAgpDeviceId(info->drmFD);
+    CARD32 agp_status = INREG(RADEON_AGP_STATUS) & mode;
+    Bool is_v3 = (agp_status & RADEON_AGPv3_MODE);
+    unsigned int defaultMode;
+    MessageType from;
+
+    if (is_v3) {
+	defaultMode = (agp_status & RADEON_AGPv3_8X_MODE) ? 8 : 4;
+    } else {
+	if (agp_status & RADEON_AGP_4X_MODE) defaultMode = 4;
+	else if (agp_status & RADEON_AGP_2X_MODE) defaultMode = 2;
+	else defaultMode = 1;
+    }
+
+    from = X_DEFAULT;
+
+    if (xf86GetOptValInteger(info->Options, OPTION_AGP_MODE, &info->agpMode)) {
+	if (info->agpMode < is_v3 ? 4 : 1 || info->agpMode > is_v3 ? 8 : 4 ||
+	    info->agpMode & (info->agpMode - 1)) {
+	    xf86DrvMsg(pScreen->myNum, X_ERROR,
+		       "Illegal AGP Mode: %d (valid values: %s), leaving at "
+		       "%dx\n", info->agpMode, is_v3 ? "4, 8" : "1, 2, 4",
+		       defaultMode);
+	    info->agpMode = defaultMode;
+	} else
+	    from = X_CONFIG;
+    } else
+	info->agpMode = defaultMode;
+
+    xf86DrvMsg(pScreen->myNum, from, "Using AGP %dx\n", info->agpMode);
+
+    info->agpFastWrite = (agp_status & RADEON_AGP_FW_MODE);
+
+    from = xf86GetOptValInteger(info->Options, OPTION_AGP_FW,
+				&info->agpFastWrite) ? X_CONFIG : X_DEFAULT;
+
+    if (info->agpFastWrite &&
+	(vendor == PCI_VENDOR_AMD) &&
+	(device == PCI_CHIP_AMD761)) {
+
+	/* Disable fast write for AMD 761 chipset, since they cause
+	 * lockups when enabled.
+	 */
+	info->agpFastWrite = FALSE;
+	from = X_DEFAULT;
+	xf86DrvMsg(pScreen->myNum, X_WARNING,
+		   "[agp] Not enabling Fast Writes on AMD 761 chipset to avoid "
+		   "lockups");
+    }
+
+    xf86DrvMsg(pScreen->myNum, from, "AGP Fast Writes %sabled\n",
+	       info->agpFastWrite ? "en" : "dis");
 
     mode &= ~RADEON_AGP_MODE_MASK;
-    if ((mode & RADEON_AGPv3_MODE) &&
-	(INREG(RADEON_AGP_STATUS) & RADEON_AGPv3_MODE)) {
+    if (is_v3) {
 	/* only set one mode bit for AGPv3 */
 	switch (info->agpMode) {
 	case 8:          mode |= RADEON_AGPv3_8X_MODE; break;
@@ -743,19 +793,6 @@ static Bool RADEONSetAgpMode(RADEONInfoPtr info, ScreenPtr pScreen)
 	}
     }
 
-    if (info->agpFastWrite &&
-	(vendor == PCI_VENDOR_AMD) &&
-	(device == PCI_CHIP_AMD761)) {
-
-	/* Disable fast write for AMD 761 chipset, since they cause
-	 * lockups when enabled.
-	 */
-	info->agpFastWrite = FALSE;
-	xf86DrvMsg(pScreen->myNum, X_WARNING,
-		   "[agp] Not enabling Fast Writes on AMD 761 chipset to avoid "
-		   "lockups");
-    }
-
     if (info->agpFastWrite) mode |= RADEON_AGP_FW_MODE;
 
     xf86DrvMsg(pScreen->myNum, X_INFO,