自学教程：C++ vfp_enable函数代码示例

static int vfp_hotplug_notifier(struct notifier_block *b, unsigned long action,				void *data){	if (action == CPU_STARTING)		vfp_enable(NULL);	return NOTIFY_OK;}

static void vfp_pm_resume(void){	/* ensure we have access to the vfp */	vfp_enable(NULL);	/* and disable it to ensure the next usage restores the state */	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);}

void vfp_pm_resume(void){		vfp_enable(NULL);		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);}

static int vfp_hotplug(struct notifier_block *b, unsigned long action,	void *hcpu){	if (action == CPU_DYING || action == CPU_DYING_FROZEN) {		vfp_force_reload((long)hcpu, current_thread_info());	} else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)		vfp_enable(NULL);	return NOTIFY_OK;}

/* * VFP support code initialisation. */static int __init vfp_init(void){	unsigned int vfpsid;	unsigned int cpu_arch = cpu_architecture();	if (cpu_arch >= CPU_ARCH_ARMv6)		vfp_enable(NULL);	/*	 * First check that there is a VFP that we can use.	 * The handler is already setup to just log calls, so	 * we just need to read the VFPSID register.	 */	vfp_vector = vfp_testing_entry;	barrier();	vfpsid = fmrx(FPSID);	barrier();	vfp_vector = vfp_null_entry;	printk(KERN_INFO "VFP support v0.3: ");	if (VFP_arch)		printk("not present/n");	else if (vfpsid & FPSID_NODOUBLE) {		printk("no double precision support/n");	} else {		smp_call_function(vfp_enable, NULL, 1);		VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT;  /* Extract the architecture version */		printk("implementor %02x architecture %d part %02x variant %x rev %x/n",			(vfpsid & FPSID_IMPLEMENTER_MASK) >> FPSID_IMPLEMENTER_BIT,			(vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT,			(vfpsid & FPSID_PART_MASK) >> FPSID_PART_BIT,			(vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT,			(vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT);		vfp_vector = vfp_support_entry;		thread_register_notifier(&vfp_notifier_block);		vfp_pm_init();		/*		 * We detected VFP, and the support code is		 * in place; report VFP support to userspace.		 */		elf_hwcap |= HWCAP_VFP;#ifdef CONFIG_NEON		/*		 * Check for the presence of the Advanced SIMD		 * load/store instructions, integer and single		 * precision floating point operations.		 */		if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)			elf_hwcap |= HWCAP_NEON;#endif	}	return 0;}

/* * VFP hardware can lose all context when a CPU goes offline. * As we will be running in SMP mode with CPU hotplug, we will save the * hardware state at every thread switch.  We clear our held state when * a CPU has been killed, indicating that the VFP hardware doesn't contain * a threads VFP state.  When a CPU starts up, we re-enable access to the * VFP hardware. * * Both CPU_DYING and CPU_STARTING are called on the CPU which * is being offlined/onlined. */static int vfp_hotplug(struct notifier_block *b, unsigned long action,	void *hcpu){	if (action == CPU_DYING || action == CPU_DYING_FROZEN)		vfp_current_hw_state[(long)hcpu] = NULL;	else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)		vfp_enable(NULL);	return NOTIFY_OK;}

static int vfp_pm_resume(struct sys_device *dev){	/* ensure we have access to the vfp */	vfp_enable(NULL);	/* and disable it to ensure the next usage restores the state */	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);	return 0;}

/* * VFP hardware can lose all context when a CPU goes offline. * As we will be running in SMP mode with CPU hotplug, we will save the * hardware state at every thread switch.  We clear our held state when * a CPU has been killed, indicating that the VFP hardware doesn't contain * a threads VFP state.  When a CPU starts up, we re-enable access to the * VFP hardware. * * Both CPU_DYING and CPU_STARTING are called on the CPU which * is being offlined/onlined. */static int vfp_hotplug(struct notifier_block *b, unsigned long action,	void *hcpu){	if (action == CPU_DYING || action == CPU_DYING_FROZEN) {		unsigned int cpu = (long)hcpu;		last_VFP_context[cpu] = NULL;	} else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)		vfp_enable(NULL);	return NOTIFY_OK;}

int vfp_flush_context(void){	unsigned long flags;	struct thread_info *ti;	u32 fpexc;	u32 cpu;	int saved = 0;	local_irq_save(flags);	ti = current_thread_info();	fpexc = fmrx(FPEXC);	cpu = ti->cpu;#ifdef CONFIG_SMP	/* On SMP, if VFP is enabled, save the old state */	if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu]) {		vfp_current_hw_state[cpu]->hard.cpu = cpu;#else	/* If there is a VFP context we must save it. */	if (vfp_current_hw_state[cpu]) {		/* Enable VFP so we can save the old state. */		fmxr(FPEXC, fpexc | FPEXC_EN);		isb();#endif		vfp_save_state(vfp_current_hw_state[cpu], fpexc);		/* disable, just in case */		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);		saved = 1;	} else if (vfp_current_hw_state[ti->cpu]) {#ifndef CONFIG_SMP		fmxr(FPEXC, fpexc | FPEXC_EN);		vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc);		fmxr(FPEXC, fpexc);#endif	}	vfp_current_hw_state[cpu] = NULL;	/* clear any information we had about last context state */	vfp_current_hw_state[ti->cpu] = NULL;	local_irq_restore(flags);	return saved;}void vfp_reinit(void){	/* ensure we have access to the vfp */	vfp_enable(NULL);	/* and disable it to ensure the next usage restores the state */	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);}

static int vfp_pm_resume(struct sys_device *dev){	unsigned int cpu_arch = cpu_architecture();	/* ensure we have access to the vfp */	if (cpu_arch >= CPU_ARCH_ARMv6) {		vfp_enable(NULL);	}	/* and disable it to ensure the next usage restores the state */	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);	return 0;}

void vfp_pm_save_context(void){	u32 fpexc = fmrx(FPEXC);	unsigned int cpu = get_cpu();	/* Save last_VFP_context if needed */	if (last_VFP_context[cpu]) {		/* Enable vfp to save context */		if (!(fpexc & FPEXC_EN)) {			vfp_enable(NULL);			fmxr(FPEXC, fpexc | FPEXC_EN);		}		vfp_save_state(last_VFP_context[cpu], fpexc);		/* disable, just in case */		fmxr(FPEXC, fpexc & ~FPEXC_EN);		last_VFP_context[cpu] = NULL;	}	put_cpu();}

int vfp_flush_context(void){	struct thread_info *ti = current_thread_info();	u32 fpexc = fmrx(FPEXC);	u32 cpu = ti->cpu;	int saved = 0;#ifdef CONFIG_SMP	/* On SMP, if VFP is enabled, save the old state */	if ((fpexc & FPEXC_EN) && last_VFP_context[cpu]) {#else	/* If there is a VFP context we must save it. */	if (last_VFP_context[cpu]) {		/* Enable VFP so we can save the old state. */		fmxr(FPEXC, fpexc | FPEXC_EN);		isb();#endif		vfp_save_state(last_VFP_context[cpu], fpexc);		/* disable, just in case */		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);		last_VFP_context[cpu] = NULL;		saved = 1;	}	return saved;}void vfp_reinit(void){	/* ensure we have access to the vfp */	vfp_enable(NULL);	/* and disable it to ensure the next usage restores the state */	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);}

/* * VFP support code initialisation. */static int __init vfp_init(void){	unsigned int vfpsid;	unsigned int cpu_arch = cpu_architecture();	if (cpu_arch >= CPU_ARCH_ARMv6)		vfp_enable(NULL);	/*	 * First check that there is a VFP that we can use.	 * The handler is already setup to just log calls, so	 * we just need to read the VFPSID register.	 */	vfp_vector = vfp_testing_entry;	barrier();	vfpsid = fmrx(FPSID);	barrier();	vfp_vector = vfp_null_entry;	printk(KERN_INFO "VFP support v0.3: ");	if (VFP_arch)		printk("not present/n");	else if (vfpsid & FPSID_NODOUBLE) {		printk("no double precision support/n");	} else {		hotcpu_notifier(vfp_hotplug, 0);		smp_call_function(vfp_enable, NULL, 1);		VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT;  /* Extract the architecture version */		printk("implementor %02x architecture %d part %02x variant %x rev %x/n",			(vfpsid & FPSID_IMPLEMENTER_MASK) >> FPSID_IMPLEMENTER_BIT,			(vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT,			(vfpsid & FPSID_PART_MASK) >> FPSID_PART_BIT,			(vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT,			(vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT);		vfp_vector = vfp_support_entry;		thread_register_notifier(&vfp_notifier_block);		vfp_pm_init();		/*		 * We detected VFP, and the support code is		 * in place; report VFP support to userspace.		 */		elf_hwcap |= HWCAP_VFP;#ifdef CONFIG_VFPv3		if (VFP_arch >= 2) {			elf_hwcap |= HWCAP_VFPv3;			/*			 * Check for VFPv3 D16 and VFPv4 D16.  CPUs in			 * this configuration only have 16 x 64bit			 * registers.			 */			if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1)				elf_hwcap |= HWCAP_VFPv3D16; /* also v4-D16 */		}#endif		/*		 * Check for the presence of the Advanced SIMD		 * load/store instructions, integer and single		 * precision floating point operations. Only check		 * for NEON if the hardware has the MVFR registers.		 */		if ((read_cpuid_id() & 0x000f0000) == 0x000f0000) {#ifdef CONFIG_NEON			if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)				elf_hwcap |= HWCAP_NEON;#endif			if ((fmrx(MVFR1) & 0xf0000000) == 0x10000000 ||			    (read_cpuid_id() & 0xff00fc00) == 0x51000400)				elf_hwcap |= HWCAP_VFPv4;		}	}	return 0;}