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Commit | Line | Data |
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2cb7cef9 BS |
1 | From: Mark Langsdorf <mark.langsdorf@amd.com> |
2 | Subject: X86 powernow-k8 cpufreq: Get transition latency from acpi _PSS object | |
3 | References: bnc#464461 | |
4 | Patch-Mainline: not yet | |
5 | ||
6 | The ondemand kernel governor calculates the best sampling rate (how often | |
7 | to check for CPU load) from the CPU transition latency it gets from the | |
8 | low level cpufreq drivers. Powernow-k8 returned too high values resulting | |
9 | in poor performance. | |
10 | ||
11 | The transition latency returned from the ACPI _PSS object is also used by | |
12 | AMD's Windows PowerNow driver (thus should always be sane) and returns more | |
13 | exact values than the previous, algorithm to guess the transition latency. | |
14 | ||
15 | Signed-off-by: Thomas Renninger <trenn@suse.de> | |
16 | ||
17 | --- | |
18 | arch/x86/kernel/cpu/cpufreq/powernow-k8.c | 30 ++++++++++++++++++++++++------ | |
19 | 1 file changed, 24 insertions(+), 6 deletions(-) | |
20 | ||
21 | Index: linux-2.6.27/arch/x86/kernel/cpu/cpufreq/powernow-k8.c | |
22 | =================================================================== | |
23 | --- linux-2.6.27.orig/arch/x86/kernel/cpu/cpufreq/powernow-k8.c | |
24 | +++ linux-2.6.27/arch/x86/kernel/cpu/cpufreq/powernow-k8.c | |
25 | @@ -927,10 +927,23 @@ static void powernow_k8_cpu_exit_acpi(st | |
26 | acpi_processor_unregister_performance(&data->acpi_data, data->cpu); | |
27 | } | |
28 | ||
29 | +static int get_transition_latency(struct powernow_k8_data *data) | |
30 | +{ | |
31 | + int max_latency = 0; | |
32 | + int i; | |
33 | + for (i = 0; i < data->acpi_data.state_count; i++) { | |
34 | + int cur_latency = data->acpi_data.states[i].transition_latency | |
35 | + + data->acpi_data.states[i].bus_master_latency; | |
36 | + if (cur_latency > max_latency) | |
37 | + max_latency = cur_latency; | |
38 | + } | |
39 | + return max_latency; | |
40 | +} | |
41 | #else | |
42 | static int powernow_k8_cpu_init_acpi(struct powernow_k8_data *data) { return -ENODEV; } | |
43 | static void powernow_k8_cpu_exit_acpi(struct powernow_k8_data *data) { return; } | |
44 | static void powernow_k8_acpi_pst_values(struct powernow_k8_data *data, unsigned int index) { return; } | |
45 | +static int get_transition_latency(struct powernow_k8_data *data) { return 0; } | |
46 | #endif /* CONFIG_X86_POWERNOW_K8_ACPI */ | |
47 | ||
48 | /* Take a frequency, and issue the fid/vid transition command */ | |
49 | @@ -1030,6 +1043,7 @@ static int powernowk8_target(struct cpuf | |
50 | unsigned int newstate; | |
51 | int ret = -EIO; | |
52 | ||
53 | + | |
54 | if (!data) | |
55 | return -EINVAL; | |
56 | ||
57 | @@ -1161,7 +1175,16 @@ static int __cpuinit powernowk8_cpu_init | |
58 | kfree(data); | |
59 | return -ENODEV; | |
60 | } | |
61 | - } | |
62 | + /* Take a crude guess here. | |
63 | + * That guess was in microseconds, so multiply with 1000 */ | |
64 | + pol->cpuinfo.transition_latency = ( | |
65 | + ( (data->rvo + 8) * data->vstable * VST_UNITS_20US) + | |
66 | + ( (1 << data->irt) * 30) | |
67 | + ) * 1000; | |
68 | + } | |
69 | + else /* ACPI _PSS objects available */ | |
70 | + pol->cpuinfo.transition_latency = | |
71 | + get_transition_latency(data) * 1000; | |
72 | ||
73 | /* only run on specific CPU from here on */ | |
74 | oldmask = current->cpus_allowed; | |
75 | @@ -1192,11 +1215,6 @@ static int __cpuinit powernowk8_cpu_init | |
76 | pol->cpus = per_cpu(cpu_core_map, pol->cpu); | |
77 | data->available_cores = &(pol->cpus); | |
78 | ||
79 | - /* Take a crude guess here. | |
80 | - * That guess was in microseconds, so multiply with 1000 */ | |
81 | - pol->cpuinfo.transition_latency = (((data->rvo + 8) * data->vstable * VST_UNITS_20US) | |
82 | - + (3 * (1 << data->irt) * 10)) * 1000; | |
83 | - | |
84 | if (cpu_family == CPU_HW_PSTATE) | |
85 | pol->cur = find_khz_freq_from_pstate(data->powernow_table, data->currpstate); | |
86 | else |