[coreboot-gerrit] New patch to review for coreboot: nb/intel/sandybridge/romstage: Read fuse bits for max MEM Clk

[Patrick Rudolph (siro@das-labor.org)]

Patrick Rudolph (siro at das-labor.org) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/13487

-gerrit

commit 65bedcf9b5efb47548bdf8c8c373fa207cfdd4e2
Author: Patrick Rudolph <siro at das-labor.org>
Date:   Tue Jan 26 20:02:14 2016 +0100

    nb/intel/sandybridge/romstage: Read fuse bits for max MEM Clk
    
    Instead of hardcoding the maximum supported DDR frequency to
    800Mhz (DDR3-1600), read the fuse bits that encode this information.
    
    Test system:
     * Intel IvyBridge
     * Gigabyte GA-B75M-D3H
    
    Change-Id: I515a2695a490f16aeb946bfaf3a1e860c607cba9
    Signed-off-by: Patrick Rudolph <siro at das-labor.org>
---
 src/include/device/dram/ddr3.h               |  4 ++-
 src/northbridge/intel/sandybridge/romstage.c | 46 +++++++++++++++++++---------
 2 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/src/include/device/dram/ddr3.h b/src/include/device/dram/ddr3.h
index de75aee..525f497 100644
--- a/src/include/device/dram/ddr3.h
+++ b/src/include/device/dram/ddr3.h
@@ -33,8 +33,10 @@
  * These values are in 1/256 ns units.
  * @{
  */
+#define TCK_1333MHZ     192
+#define TCK_1200MHZ     212
 #define TCK_1066MHZ     240
-#define TCK_933MHZ	275
+#define TCK_933MHZ      275
 #define TCK_800MHZ      320
 #define TCK_666MHZ      384
 #define TCK_533MHZ      480
diff --git a/src/northbridge/intel/sandybridge/romstage.c b/src/northbridge/intel/sandybridge/romstage.c
index 34d759f..d1fedc7 100644
--- a/src/northbridge/intel/sandybridge/romstage.c
+++ b/src/northbridge/intel/sandybridge/romstage.c
@@ -36,30 +36,48 @@
 
 #define HOST_BRIDGE	PCI_DEVFN(0, 0)
 #define DEFAULT_TCK	TCK_800MHZ
+#define CAPID0_B 0xe8
 
 static unsigned int get_mem_min_tck(void)
 {
+	u32 reg32;
 	const struct device *dev;
 	const struct northbridge_intel_sandybridge_config *cfg;
 
 	dev = dev_find_slot(0, HOST_BRIDGE);
-	if (!(dev && dev->chip_info))
-		return DEFAULT_TCK;
-
-	cfg = dev->chip_info;
+	cfg = NULL;
+	if (dev)
+		cfg = dev->chip_info;
 
 	/* If this is zero, it just means devicetree.cb didn't set it */
-	if (cfg->max_mem_clock_mhz == 0)
+	if (!cfg || cfg->max_mem_clock_mhz == 0) {
+		/* read Capabilities B Register DMFC bits */
+		reg32 = pci_read_config32(PCI_DEV(0, 0, 0), CAPID0_B);
+		reg32 = (reg32 >> 4) & 0x7;
+
+		switch (reg32) {
+		case 7: return TCK_533MHZ;
+		case 6: return TCK_666MHZ;
+		case 5: return TCK_800MHZ;
+		case 4: return TCK_933MHZ;
+		case 3: return TCK_1066MHZ;
+		case 2: return TCK_1200MHZ;
+		case 1: return TCK_1333MHZ;
+		/* reserved: */
+		default:
+			break;
+		}
 		return DEFAULT_TCK;
-
-	if (cfg->max_mem_clock_mhz >= 800)
-		return TCK_800MHZ;
-	else if (cfg->max_mem_clock_mhz >= 666)
-		return TCK_666MHZ;
-	else if (cfg->max_mem_clock_mhz >= 533)
-		return TCK_533MHZ;
-	else
-		return TCK_400MHZ;
+	} else {
+		if (cfg->max_mem_clock_mhz >= 800)
+			return TCK_800MHZ;
+		else if (cfg->max_mem_clock_mhz >= 666)
+			return TCK_666MHZ;
+		else if (cfg->max_mem_clock_mhz >= 533)
+			return TCK_533MHZ;
+		else
+			return TCK_400MHZ;
+	}
 }
 
 void main(unsigned long bist)