Commit 5a7ae78f authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86: Allow platforms to force enable apic 



Some embedded x86 platforms don't setup the APIC in the
BIOS/bootloader and would be forced to add "lapic" on the kernel
command line. That's a bit akward.

Split out the force enable code from detect_init_APIC() and allow
platform code to call it from the platform setup. That avoids the
command line parameter and possible replication of the MSR dance in
the force enable code.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
LKML-Reference: <1287510389-8388-1-git-send-email-dirk.brandewie@gmail.com>
Signed-off-by: default avatarDirk Brandewie <dirk.j.brandewie@intel.com>
parent d4429f60

arch/x86/include/asm/apic.h

+1 −0
Original line number Diff line number Diff line
@@ -238,6 +238,7 @@ extern void setup_boot_APIC_clock(void); 
extern void setup_secondary_APIC_clock(void);

extern int APIC_init_uniprocessor(void);

extern void enable_NMI_through_LVT0(void);

extern int apic_force_enable(void);



/*

 * On 32bit this is mach-xxx local

arch/x86/kernel/apic/apic.c

+54 −33
Original line number Diff line number Diff line
@@ -1531,13 +1531,60 @@ static int __init detect_init_APIC(void) 
	return 0;

}

#else



static int apic_verify(void)

{

	u32 features, h, l;



	/*

	 * The APIC feature bit should now be enabled

	 * in `cpuid'

	 */

	features = cpuid_edx(1);

	if (!(features & (1 << X86_FEATURE_APIC))) {

		pr_warning("Could not enable APIC!\n");

		return -1;

	}

	set_cpu_cap(&boot_cpu_data, X86_FEATURE_APIC);

	mp_lapic_addr = APIC_DEFAULT_PHYS_BASE;



	/* The BIOS may have set up the APIC at some other address */

	rdmsr(MSR_IA32_APICBASE, l, h);

	if (l & MSR_IA32_APICBASE_ENABLE)

		mp_lapic_addr = l & MSR_IA32_APICBASE_BASE;



	pr_info("Found and enabled local APIC!\n");

	return 0;

}



int apic_force_enable(void)

{

	u32 h, l;



	if (disable_apic)

		return -1;



	/*

	 * Some BIOSes disable the local APIC in the APIC_BASE

	 * MSR. This can only be done in software for Intel P6 or later

	 * and AMD K7 (Model > 1) or later.

	 */

	rdmsr(MSR_IA32_APICBASE, l, h);

	if (!(l & MSR_IA32_APICBASE_ENABLE)) {

		pr_info("Local APIC disabled by BIOS -- reenabling.\n");

		l &= ~MSR_IA32_APICBASE_BASE;

		l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;

		wrmsr(MSR_IA32_APICBASE, l, h);

		enabled_via_apicbase = 1;

	}

	return apic_verify();

}



/*

 * Detect and initialize APIC

 */

static int __init detect_init_APIC(void)

{

	u32 h, l, features;



	/* Disabled by kernel option? */

	if (disable_apic)

		return -1;
@@ -1567,38 +1614,12 @@ static int __init detect_init_APIC(void) 
				"you can enable it with \"lapic\"\n");

			return -1;

		}

		/*

		 * Some BIOSes disable the local APIC in the APIC_BASE

		 * MSR. This can only be done in software for Intel P6 or later

		 * and AMD K7 (Model > 1) or later.

		 */

		rdmsr(MSR_IA32_APICBASE, l, h);

		if (!(l & MSR_IA32_APICBASE_ENABLE)) {

			pr_info("Local APIC disabled by BIOS -- reenabling.\n");

			l &= ~MSR_IA32_APICBASE_BASE;

			l |= MSR_IA32_APICBASE_ENABLE | APIC_DEFAULT_PHYS_BASE;

			wrmsr(MSR_IA32_APICBASE, l, h);

			enabled_via_apicbase = 1;

		}

	}

	/*

	 * The APIC feature bit should now be enabled

	 * in `cpuid'

	 */

	features = cpuid_edx(1);

	if (!(features & (1 << X86_FEATURE_APIC))) {

		pr_warning("Could not enable APIC!\n");

		if (apic_force_enable())

			return -1;

	} else {

		if (apic_verify())

			return -1;

	}

	set_cpu_cap(&boot_cpu_data, X86_FEATURE_APIC);

	mp_lapic_addr = APIC_DEFAULT_PHYS_BASE;



	/* The BIOS may have set up the APIC at some other address */

	rdmsr(MSR_IA32_APICBASE, l, h);

	if (l & MSR_IA32_APICBASE_ENABLE)

		mp_lapic_addr = l & MSR_IA32_APICBASE_BASE;



	pr_info("Found and enabled local APIC!\n");



	apic_pm_activate();

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