diff options
| author | Patrick Rudolph <siro@das-labor.org> | 2016-11-11 19:17:56 +0100 |
|---|---|---|
| committer | Patrick Rudolph <siro@das-labor.org> | 2016-11-20 14:59:59 +0100 |
| commit | bec669685cdd77e12cdf8fad2e68d39218cfdba7 (patch) | |
| tree | 497874d9ba7d28ad87b6899f159dfcda4e81798c /src/northbridge | |
| parent | 78c5f0cc029ab877ab5bf018abed18684c038602 (diff) | |
nb/intel/sandybridge/raminit: Fix CAS Write Latency
As documented in DDR3 spec for MR2 the CWL is based on DDR frequency.
There's no to little difference for most memory modules operating at DDR3-1333.
It might fix problems for memory modules that operate at a higher frequency and
memory modules with low CL values should work even better.
Tested on Lenovo T420 with DDR3-1333 CL9 and DDR3-1600 CL11.
No regressions found.
Change-Id: Ib90b5de872a219cf80b4976b6dfae6bc02e298f4
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/17389
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Diffstat (limited to 'src/northbridge')
| -rw-r--r-- | src/northbridge/intel/sandybridge/raminit.c | 38 |
1 files changed, 27 insertions, 11 deletions
diff --git a/src/northbridge/intel/sandybridge/raminit.c b/src/northbridge/intel/sandybridge/raminit.c index 46dc7c7843..8123014e91 100644 --- a/src/northbridge/intel/sandybridge/raminit.c +++ b/src/northbridge/intel/sandybridge/raminit.c @@ -491,17 +491,33 @@ static void dram_find_common_params(ramctr_timing *ctrl) die("No valid DIMMs found"); } -static u8 get_CWL(u8 CAS) +/* CAS write latency. To be programmed in MR2. + * See DDR3 SPEC for MR2 documentation. */ +static u8 get_CWL(u32 tCK) { - /* Get CWL based on CAS using the following rule: - * _________________________________________ - * CAS: | 4T | 5T | 6T | 7T | 8T | 9T | 10T | 11T | - * CWL: | 5T | 5T | 5T | 6T | 6T | 7T | 7T | 8T | - */ - static const u8 cas_cwl_map[] = { 5, 5, 5, 6, 6, 7, 7, 8 }; - if (CAS > 11) + /* Get CWL based on tCK using the following rule: */ + switch (tCK) { + case TCK_1333MHZ: + return 12; + case TCK_1200MHZ: + case TCK_1100MHZ: + return 11; + case TCK_1066MHZ: + case TCK_1000MHZ: + return 10; + case TCK_933MHZ: + case TCK_900MHZ: + return 9; + case TCK_800MHZ: + case TCK_700MHZ: return 8; - return cas_cwl_map[CAS - 4]; + case TCK_666MHZ: + return 7; + case TCK_533MHZ: + return 6; + default: + return 5; + } } /* Frequency multiplier. */ @@ -713,7 +729,7 @@ static void dram_timing(ramctr_timing * ctrl) val32 = (1000 << 8) / ctrl->tCK; printk(BIOS_DEBUG, "Selected DRAM frequency: %u MHz\n", val32); - /* Find CAS and CWL latencies */ + /* Find CAS latency */ val = (ctrl->tAA + ctrl->tCK - 1) / ctrl->tCK; printk(BIOS_DEBUG, "Minimum CAS latency : %uT\n", val); /* Find lowest supported CAS latency that satisfies the minimum value */ @@ -734,7 +750,7 @@ static void dram_timing(ramctr_timing * ctrl) printk(BIOS_DEBUG, "Selected CAS latency : %uT\n", val); ctrl->CAS = val; - ctrl->CWL = get_CWL(ctrl->CAS); + ctrl->CWL = get_CWL(ctrl->tCK); printk(BIOS_DEBUG, "Selected CWL latency : %uT\n", ctrl->CWL); /* Find tRCD */ |