Patch set updated for coreboot: device/dram/ddr2: Add function to select common CAS en freq

[Arthur Heymans]

Arthur Heymans ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/18320

-gerrit

commit 38870e4f8a07064659fc0da5104ad08d738b7eaf
Author: Arthur Heymans 
Date:   Fri Feb 10 12:08:16 2017 +0100

device/dram/ddr2: Add function to select common CAS en freq

This function finds highest common CAS and select tCLK based on
    the dimm with highest minumum tCLK at that selected CAS.

Change-Id: I3ab39d38a243edddfde8f70ebd23f79ff774e90e
    Signed-off-by: Arthur Heymans 
---
 src/device/dram/ddr2.c         | 57 ++++++++++++++++++++++++++++++++++++++++++
 src/include/device/dram/ddr2.h |  3 ++-
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/src/device/dram/ddr2.c b/src/device/dram/ddr2.c
index c2bfe0c..835546f 100644
--- a/src/device/dram/ddr2.c
+++ b/src/device/dram/ddr2.c
@@ -2,6 +2,7 @@
  * This file is part of the coreboot project.
  *
  * Copyright (C) 2017 Patrick Rudolph 
+ * Copyright (C) 2017 Arthur Heymans 
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -635,3 +636,59 @@ void dram_print_spd_ddr2(const dimm_attr *dimm)
    print_us("  tPLL              : ", dimm->tPLL);
    print_us("  tRR               : ", dimm->tRR);
 }
+
+u32 get_common_freq_cas(u8 cas_mask, const dimm_attr *dimm, int num_dimms,
+			u8 *selected_cas)
+{
+	int i, high_common_cas;
+	u32 tCLK = 0;
+
+	for (i = 0; i < num_dimms; i++) {
+		if (dimm[i].dimm_type == SPD_DIMM_TYPE_UNDEFINED)
+			continue;
+		cas_mask &= dimm[i].cas_supported;
+	}
+
+	if (!cas_mask) {
+		printk(BIOS_DEBUG, "No common supported CAS\n");
+		return 0;
+	}
+
+	high_common_cas = spd_get_msbs(cas_mask);
+	for (i = 0; i < num_dimms; i++) {
+		if (dimm[i].dimm_type == SPD_DIMM_TYPE_UNDEFINED)
+			continue;
+		if (dimm[i].cycle_time[high_common_cas] == 0)
+			printk(BIOS_DEBUG, "No minimum tCLK defined for dimm %d at CAS %d\n",
+				i, high_common_cas);
+		if (tCLK < dimm[i].cycle_time[high_common_cas])
+			tCLK = dimm[i].cycle_time[high_common_cas];
+	}
+
+	if (tCLK == 0) {
+		printk(BIOS_DEBUG, "No valid minimum tCLK found\n");
+		return 0;
+	}
+
+	if (tCLK <= TCK_800MHZ) {
+		tCLK = TCK_800MHZ;
+	} else if (tCLK <= TCK_666MHZ) {
+		tCLK = TCK_666MHZ;
+	} else if (tCLK <= TCK_533MHZ) {
+		tCLK = TCK_533MHZ;
+	} else if (tCLK <= TCK_400MHZ) {
+		tCLK = TCK_400MHZ;
+	} else if (tCLK <= TCK_333MHZ) {
+		tCLK = TCK_333MHZ;
+	} else if (tCLK <= TCK_266MHZ) {
+		tCLK = TCK_266MHZ;
+	} else if (tCLK <= TCK_200MHZ) {
+		tCLK = TCK_200MHZ;
+	} else {
+		printk(BIOS_DEBUG, "Too slow common tCLK found\n");
+		return 0;
+	}
+
+	*selected_cas = high_common_cas;
+	return tCLK;
+}
diff --git a/src/include/device/dram/ddr2.h b/src/include/device/dram/ddr2.h
index ae02c40..4c33b1b 100644
--- a/src/include/device/dram/ddr2.h
+++ b/src/include/device/dram/ddr2.h
@@ -210,6 +210,7 @@ u32 spd_decode_spd_size_ddr2(u8 byte0);
 u32 spd_decode_eeprom_size_ddr2(u8 byte1);
 int spd_decode_ddr2(dimm_attr *dimm, spd_raw_data spd);
 void dram_print_spd_ddr2(const dimm_attr *dimm);
-
+u32 get_common_freq_cas(u8 cas_mask, const dimm_attr *dimm, int num_dimms,
+			 u8 *selected_cas);

#endif /* DEVICE_DRAM_DDR2L_H */