[patch 05/56] agp/intel: Reduce extraneous PCI posting readsduring init

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.
------------------

From: Keith Packard <keithp@xxxxxxxxxx>

commit 44d494417278e49f5b42bd3ded1801b6d2254db8 upstream.

Instead of doing a posting read after each GTT entry update, do a single one
at the end of the writes. This should reduce boot time a tiny amount by
avoiding a lot of extra uncached reads.

Signed-off-by: Keith Packard <keithp@xxxxxxxxxx>
Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/char/agp/intel-agp.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/char/agp/intel-agp.c
+++ b/drivers/char/agp/intel-agp.c
@@ -217,8 +217,8 @@ static int intel_i810_configure(void)
 	if (agp_bridge->driver->needs_scratch_page) {
 		for (i = 0; i < current_size->num_entries; i++) {
 			writel(agp_bridge->scratch_page, intel_private.registers+I810_PTE_BASE+(i*4));
-			readl(intel_private.registers+I810_PTE_BASE+(i*4));	/* PCI posting. */
 		}
+		readl(intel_private.registers+I810_PTE_BASE+((i-1)*4));	/* PCI posting. */
 	}
 	global_cache_flush();
 	return 0;
@@ -778,8 +778,8 @@ static int intel_i830_configure(void)
 	if (agp_bridge->driver->needs_scratch_page) {
 		for (i = intel_private.gtt_entries; i < current_size->num_entries; i++) {
 			writel(agp_bridge->scratch_page, intel_private.registers+I810_PTE_BASE+(i*4));
-			readl(intel_private.registers+I810_PTE_BASE+(i*4));	/* PCI Posting. */
 		}
+		readl(intel_private.registers+I810_PTE_BASE+((i-1)*4));	/* PCI Posting. */
 	}
 
 	global_cache_flush();
@@ -994,8 +994,8 @@ static int intel_i915_configure(void)
 	if (agp_bridge->driver->needs_scratch_page) {
 		for (i = intel_private.gtt_entries; i < current_size->num_entries; i++) {
 			writel(agp_bridge->scratch_page, intel_private.gtt+i);
-			readl(intel_private.gtt+i);	/* PCI Posting. */
 		}
+		readl(intel_private.gtt+i-1);	/* PCI Posting. */
 	}
 
 	global_cache_flush();

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