agp/intel: Experiment with a 855GM GWB bit
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=27187
Tested-by: Thorsten Vollmer <thorsten@thvo.de> (DFI-ACP G5M150-N w/852GME)
Tested-by: Moritz Brunner <2points@gmx.org> (Asus M2400N/i855GM)
Tested-by: Indan Zupancic <indan@nul.nu> (Thinkpad X40/855GM rev 02)
Tested-by: Eric Anholt <eric@anholt.net> (865G)
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/char/agp/intel-agp.h b/drivers/char/agp/intel-agp.h
index c195bfe..5feebe2 100644
--- a/drivers/char/agp/intel-agp.h
+++ b/drivers/char/agp/intel-agp.h
@@ -130,6 +130,7 @@
#define INTEL_GMCH_GMS_STOLEN_352M (0xd << 4)
#define I915_IFPADDR 0x60
+#define I830_HIC 0x70
/* Intel 965G registers */
#define I965_MSAC 0x62
diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
index fab3d32..0d09b53 100644
--- a/drivers/char/agp/intel-gtt.c
+++ b/drivers/char/agp/intel-gtt.c
@@ -21,6 +21,7 @@
#include <linux/kernel.h>
#include <linux/pagemap.h>
#include <linux/agp_backend.h>
+#include <linux/delay.h>
#include <asm/smp.h>
#include "agp.h"
#include "intel-agp.h"
@@ -70,12 +71,8 @@
u32 __iomem *gtt; /* I915G */
bool clear_fake_agp; /* on first access via agp, fill with scratch */
int num_dcache_entries;
- union {
- void __iomem *i9xx_flush_page;
- void *i8xx_flush_page;
- };
+ void __iomem *i9xx_flush_page;
char *i81x_gtt_table;
- struct page *i8xx_page;
struct resource ifp_resource;
int resource_valid;
struct page *scratch_page;
@@ -722,28 +719,6 @@
static void i830_cleanup(void)
{
- if (intel_private.i8xx_flush_page) {
- kunmap(intel_private.i8xx_flush_page);
- intel_private.i8xx_flush_page = NULL;
- }
-
- __free_page(intel_private.i8xx_page);
- intel_private.i8xx_page = NULL;
-}
-
-static void intel_i830_setup_flush(void)
-{
- /* return if we've already set the flush mechanism up */
- if (intel_private.i8xx_page)
- return;
-
- intel_private.i8xx_page = alloc_page(GFP_KERNEL);
- if (!intel_private.i8xx_page)
- return;
-
- intel_private.i8xx_flush_page = kmap(intel_private.i8xx_page);
- if (!intel_private.i8xx_flush_page)
- i830_cleanup();
}
/* The chipset_flush interface needs to get data that has already been
@@ -758,14 +733,27 @@
*/
static void i830_chipset_flush(void)
{
- unsigned int *pg = intel_private.i8xx_flush_page;
+ unsigned long timeout = jiffies + msecs_to_jiffies(1000);
- memset(pg, 0, 1024);
+ /* Forcibly evict everything from the CPU write buffers.
+ * clflush appears to be insufficient.
+ */
+ wbinvd_on_all_cpus();
- if (cpu_has_clflush)
- clflush_cache_range(pg, 1024);
- else if (wbinvd_on_all_cpus() != 0)
- printk(KERN_ERR "Timed out waiting for cache flush.\n");
+ /* Now we've only seen documents for this magic bit on 855GM,
+ * we hope it exists for the other gen2 chipsets...
+ *
+ * Also works as advertised on my 845G.
+ */
+ writel(readl(intel_private.registers+I830_HIC) | (1<<31),
+ intel_private.registers+I830_HIC);
+
+ while (readl(intel_private.registers+I830_HIC) & (1<<31)) {
+ if (time_after(jiffies, timeout))
+ break;
+
+ udelay(50);
+ }
}
static void i830_write_entry(dma_addr_t addr, unsigned int entry,
@@ -849,8 +837,6 @@
intel_private.gtt_bus_addr = reg_addr + I810_PTE_BASE;
- intel_i830_setup_flush();
-
return 0;
}