Commit 52a2638b authored by Rafal Bilski's avatar Rafal Bilski Committed by Linus Torvalds
Browse files

Longhaul: add auto enabled "revid_errata" option

VIA C3 Ezra-T has RevisionID equal to 1, but it needs RevisionKey to be 0
or CPU will ignore new frequency and will continue to work at old
frequency.  New "revid_errata" option will force RevisionKey to be set to
0, whatever RevisionID is.

Additionaly "Longhaul" will not silently ignore unsuccessful transition.
It will try to check if "revid_errata" or "disable_acpi_c3" options need to
be enabled for this processor/system.

Same for Longhaul ver.  2 support.  It will be disabled if none of above
options will work.

 Best case scenario (with patch apllied and v2 enabled):
 longhaul: VIA C3 'Ezra' [C5C] CPU detected.  Longhaul v2 supported.
 longhaul: Using northbridge support.
 longhaul: VRM 8.5
 longhaul: Max VID=1.350  Min VID=1.050, 13 possible voltage scales
 longhaul: f: 300000 kHz, index: 0, vid: 1050 mV
 longhaul: Voltage scaling enabled.
 Worst case scenario:
 longhaul: VIA C3 'Ezra-T' [C5M] CPU detected.  Powersaver supported.
 longhaul: Using northbridge support.
 longhaul: Using ACPI support.
 longhaul: VRM 8.5
 longhaul: Claims to support voltage scaling but min & max are both 1.250. Voltage scaling disabled
 longhaul: Failed to set requested frequency!
 longhaul: Enabling "Ignore Revision ID" option.
 longhaul: Failed to set requested frequency!
 longhaul: Disabling ACPI C3 support.
 longhaul: Disabling "Ignore Revision ID" option.
 longhaul: Failed to set requested frequency!
 longhaul: Enabling "Ignore Revision ID" option.

[ coding-style cleanups]
Signed-off-by: default avatarRafal Bilski <>
Signed-off-by: default avatarDave Jones <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 74922be1
......@@ -76,6 +76,7 @@ static unsigned int longhaul_index;
/* Module parameters */
static int scale_voltage;
static int disable_acpi_c3;
static int revid_errata;
#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "longhaul", msg)
......@@ -168,7 +169,10 @@ static void do_powersaver(int cx_address, unsigned int clock_ratio_index,
rdmsrl(MSR_VIA_LONGHAUL, longhaul.val);
/* Setup new frequency */
longhaul.bits.RevisionKey = longhaul.bits.RevisionID;
if (!revid_errata)
longhaul.bits.RevisionKey = longhaul.bits.RevisionID;
longhaul.bits.RevisionKey = 0;
longhaul.bits.SoftBusRatio = clock_ratio_index & 0xf;
longhaul.bits.SoftBusRatio4 = (clock_ratio_index & 0x10) >> 4;
/* Setup new voltage */
......@@ -272,7 +276,7 @@ static void longhaul_setstate(unsigned int table_index)
dprintk ("Setting to FSB:%dMHz Mult:%d.%dx (%s)\n",
fsb, mult/10, mult%10, print_speed(speed/1000));
......@@ -344,6 +348,47 @@ static void longhaul_setstate(unsigned int table_index)
preempt_enable(); = calc_speed(longhaul_get_cpu_mult());
/* Check if requested frequency is set. */
if (unlikely( != speed)) {
printk(KERN_INFO PFX "Failed to set requested frequency!\n");
/* Revision ID = 1 but processor is expecting revision key
* equal to 0. Jumpers at the bottom of processor will change
* multiplier and FSB, but will not change bits in Longhaul
* MSR nor enable voltage scaling. */
if (!revid_errata) {
printk(KERN_INFO PFX "Enabling \"Ignore Revision ID\" "
revid_errata = 1;
goto retry_loop;
/* Why ACPI C3 sometimes doesn't work is a mystery for me.
* But it does happen. Processor is entering ACPI C3 state,
* but it doesn't change frequency. I tried poking various
* bits in northbridge registers, but without success. */
if (longhaul_flags & USE_ACPI_C3) {
printk(KERN_INFO PFX "Disabling ACPI C3 support.\n");
longhaul_flags &= ~USE_ACPI_C3;
if (revid_errata) {
printk(KERN_INFO PFX "Disabling \"Ignore "
"Revision ID\" option.\n");
revid_errata = 0;
goto retry_loop;
/* This shouldn't happen. Longhaul ver. 2 was reported not
* working on processors without voltage scaling, but with
* RevID = 1. RevID errata will make things right. Just
* to be 100% sure. */
if (longhaul_version == TYPE_LONGHAUL_V2) {
printk(KERN_INFO PFX "Switching to Longhaul ver. 1\n");
longhaul_version = TYPE_LONGHAUL_V1;
goto retry_loop;
/* Report true CPU frequency */
cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
if (!bm_timeout)
......@@ -956,11 +1001,20 @@ static void __exit longhaul_exit(void)
/* Even if BIOS is exporting ACPI C3 state, and it is used
* with success when CPU is idle, this state doesn't
* trigger frequency transition in some cases. */
module_param (disable_acpi_c3, int, 0644);
MODULE_PARM_DESC(disable_acpi_c3, "Don't use ACPI C3 support");
/* Change CPU voltage with frequency. Very usefull to save
* power, but most VIA C3 processors aren't supporting it. */
module_param (scale_voltage, int, 0644);
MODULE_PARM_DESC(scale_voltage, "Scale voltage of processor");
/* Force revision key to 0 for processors which doesn't
* support voltage scaling, but are introducing itself as
* such. */
module_param(revid_errata, int, 0644);
MODULE_PARM_DESC(revid_errata, "Ignore CPU Revision ID");
MODULE_AUTHOR ("Dave Jones <>");
MODULE_DESCRIPTION ("Longhaul driver for VIA Cyrix processors.");
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