[CPUFREQ] Add support for Pentium M (Dothan) processors for p4-clockmod.

But warn loudly if anyone tries to use it -- you really should use speedstep-centrino
instead. On Dothans, the TSC is _not_ affected by TSC transitions (contrary
to Banias processors), so set the CPUFREQ_CONST_LOOPS flag.
                                                                                
Many thanks to Thomas Renninger for reporting the lack of, and testing
the support for Dothan processors.

arch/i386/kernel/cpu/cpufreq/p4-clockmod.c

@@ -181,7 +181,7 @@ static int cpufreq_p4_verify(struct cpufreq_policy *policy)
 static unsigned int cpufreq_p4_get_frequency(struct cpuinfo_x86 *c)
 {
 	if ((c->x86 == 0x06) && (c->x86_model == 0x09)) {
-		/* Pentium M */
+		/* Pentium M (Banias) */
 		printk(KERN_WARNING PFX "Warning: Pentium M detected. "
 		       "The speedstep_centrino module offers voltage scaling"
 		       " in addition of frequency scaling. You should use "
@@ -189,6 +189,18 @@ static unsigned int cpufreq_p4_get_frequency(struct cpuinfo_x86 *c)
 		return speedstep_get_processor_frequency(SPEEDSTEP_PROCESSOR_PM);
 	}
 
+	if ((c->x86 == 0x06) && (c->x86_model == 0x13)) {
+		/* Pentium M (Dothan) */
+		printk(KERN_WARNING PFX "Warning: Pentium M detected. "
+		       "The speedstep_centrino module offers voltage scaling"
+		       " in addition of frequency scaling. You should use "
+		       "that instead of p4-clockmod, if possible.\n");
+		/* on P-4s, the TSC runs with constant frequency independent wether
+		 * throttling is active or not. */
+		p4clockmod_driver.flags |= CPUFREQ_CONST_LOOPS;
+		return speedstep_get_processor_frequency(SPEEDSTEP_PROCESSOR_PM);
+	}
+
 	if (c->x86 != 0xF) {
 		printk(KERN_WARNING PFX "Unknown p4-clockmod-capable CPU. Please send an e-mail to <linux@brodo.de>\n");
 		return 0;