diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2008-09-04 11:18:44 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-09-04 11:35:33 -0400 |
commit | cce3e057242d3d46fea07b9eb3910b0076419be5 (patch) | |
tree | 020733ab2b7e75063ad78c0f4e1068a0dc56b409 /arch | |
parent | d210baf53b699fc61aa891c177b71d7082d3b957 (diff) |
x86: TSC: define the PIT latch value separate
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/x86/kernel/tsc.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 346cae5ac423..aa11413e7c1d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c | |||
@@ -122,6 +122,10 @@ static u64 tsc_read_refs(u64 *pm, u64 *hpet) | |||
122 | return ULLONG_MAX; | 122 | return ULLONG_MAX; |
123 | } | 123 | } |
124 | 124 | ||
125 | #define CAL_MS 50 | ||
126 | #define CAL_LATCH (CLOCK_TICK_RATE / (1000 / CAL_MS)) | ||
127 | #define CAL_PIT_LOOPS 5000 | ||
128 | |||
125 | /* | 129 | /* |
126 | * Try to calibrate the TSC against the Programmable | 130 | * Try to calibrate the TSC against the Programmable |
127 | * Interrupt Timer and return the frequency of the TSC | 131 | * Interrupt Timer and return the frequency of the TSC |
@@ -144,8 +148,8 @@ static unsigned long pit_calibrate_tsc(void) | |||
144 | * (LSB then MSB) to begin countdown. | 148 | * (LSB then MSB) to begin countdown. |
145 | */ | 149 | */ |
146 | outb(0xb0, 0x43); | 150 | outb(0xb0, 0x43); |
147 | outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42); | 151 | outb(CAL_LATCH & 0xff, 0x42); |
148 | outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42); | 152 | outb(CAL_LATCH >> 8, 0x42); |
149 | 153 | ||
150 | tsc = t1 = t2 = get_cycles(); | 154 | tsc = t1 = t2 = get_cycles(); |
151 | 155 | ||
@@ -166,18 +170,18 @@ static unsigned long pit_calibrate_tsc(void) | |||
166 | /* | 170 | /* |
167 | * Sanity checks: | 171 | * Sanity checks: |
168 | * | 172 | * |
169 | * If we were not able to read the PIT more than 5000 | 173 | * If we were not able to read the PIT more than PIT_MIN_LOOPS |
170 | * times, then we have been hit by a massive SMI | 174 | * times, then we have been hit by a massive SMI |
171 | * | 175 | * |
172 | * If the maximum is 10 times larger than the minimum, | 176 | * If the maximum is 10 times larger than the minimum, |
173 | * then we got hit by an SMI as well. | 177 | * then we got hit by an SMI as well. |
174 | */ | 178 | */ |
175 | if (pitcnt < 5000 || tscmax > 10 * tscmin) | 179 | if (pitcnt < CAL_PIT_LOOPS || tscmax > 10 * tscmin) |
176 | return ULONG_MAX; | 180 | return ULONG_MAX; |
177 | 181 | ||
178 | /* Calculate the PIT value */ | 182 | /* Calculate the PIT value */ |
179 | delta = t2 - t1; | 183 | delta = t2 - t1; |
180 | do_div(delta, 50); | 184 | do_div(delta, CAL_MS); |
181 | return delta; | 185 | return delta; |
182 | } | 186 | } |
183 | 187 | ||