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vfpmodule.c

/*
 *  linux/arch/arm/vfp/vfpmodule.c
 *
 *  Copyright (C) 2004 ARM Limited.
 *  Written by Deep Blue Solutions Limited.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/types.h>
#include <linux/cpu.h>
#include <linux/kernel.h>
#include <linux/notifier.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/init.h>

#include <asm/cputype.h>
#include <asm/thread_notify.h>
#include <asm/vfp.h>

#include "vfpinstr.h"
#include "vfp.h"

/*
 * Our undef handlers (in entry.S)
 */
void vfp_testing_entry(void);
void vfp_support_entry(void);
void vfp_null_entry(void);

void (*vfp_vector)(void) = vfp_null_entry;
union vfp_state *last_VFP_context[NR_CPUS];

/*
 * Dual-use variable.
 * Used in startup: set to non-zero if VFP checks fail
 * After startup, holds VFP architecture
 */
unsigned int VFP_arch;

/*
 * Per-thread VFP initialization.
 */
static void vfp_thread_flush(struct thread_info *thread)
{
      union vfp_state *vfp = &thread->vfpstate;
      unsigned int cpu;

      memset(vfp, 0, sizeof(union vfp_state));

      vfp->hard.fpexc = FPEXC_EN;
      vfp->hard.fpscr = FPSCR_ROUND_NEAREST;

      /*
       * Disable VFP to ensure we initialize it first.  We must ensure
       * that the modification of last_VFP_context[] and hardware disable
       * are done for the same CPU and without preemption.
       */
      cpu = get_cpu();
      if (last_VFP_context[cpu] == vfp)
            last_VFP_context[cpu] = NULL;
      fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
      put_cpu();
}

static void vfp_thread_exit(struct thread_info *thread)
{
      /* release case: Per-thread VFP cleanup. */
      union vfp_state *vfp = &thread->vfpstate;
      unsigned int cpu = get_cpu();

      if (last_VFP_context[cpu] == vfp)
            last_VFP_context[cpu] = NULL;
      put_cpu();
}

/*
 * When this function is called with the following 'cmd's, the following
 * is true while this function is being run:
 *  THREAD_NOFTIFY_SWTICH:
 *   - the previously running thread will not be scheduled onto another CPU.
 *   - the next thread to be run (v) will not be running on another CPU.
 *   - thread->cpu is the local CPU number
 *   - not preemptible as we're called in the middle of a thread switch
 *  THREAD_NOTIFY_FLUSH:
 *   - the thread (v) will be running on the local CPU, so
 *    v === current_thread_info()
 *   - thread->cpu is the local CPU number at the time it is accessed,
 *    but may change at any time.
 *   - we could be preempted if tree preempt rcu is enabled, so
 *    it is unsafe to use thread->cpu.
 *  THREAD_NOTIFY_EXIT
 *   - the thread (v) will be running on the local CPU, so
 *    v === current_thread_info()
 *   - thread->cpu is the local CPU number at the time it is accessed,
 *    but may change at any time.
 *   - we could be preempted if tree preempt rcu is enabled, so
 *    it is unsafe to use thread->cpu.
 */
static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
{
      struct thread_info *thread = v;

      if (likely(cmd == THREAD_NOTIFY_SWITCH)) {
            u32 fpexc = fmrx(FPEXC);

#ifdef CONFIG_SMP
            unsigned int cpu = thread->cpu;

            /*
             * On SMP, if VFP is enabled, save the old state in
             * case the thread migrates to a different CPU. The
             * restoring is done lazily.
             */
            if ((fpexc & FPEXC_EN) && last_VFP_context[cpu]) {
                  vfp_save_state(last_VFP_context[cpu], fpexc);
                  last_VFP_context[cpu]->hard.cpu = cpu;
            }
            /*
             * Thread migration, just force the reloading of the
             * state on the new CPU in case the VFP registers
             * contain stale data.
             */
            if (thread->vfpstate.hard.cpu != cpu)
                  last_VFP_context[cpu] = NULL;
#endif

            /*
             * Always disable VFP so we can lazily save/restore the
             * old state.
             */
            fmxr(FPEXC, fpexc & ~FPEXC_EN);
            return NOTIFY_DONE;
      }

      if (cmd == THREAD_NOTIFY_FLUSH)
            vfp_thread_flush(thread);
      else
            vfp_thread_exit(thread);

      return NOTIFY_DONE;
}

static struct notifier_block vfp_notifier_block = {
      .notifier_call    = vfp_notifier,
};

/*
 * Raise a SIGFPE for the current process.
 * sicode describes the signal being raised.
 */
void vfp_raise_sigfpe(unsigned int sicode, struct pt_regs *regs)
{
      siginfo_t info;

      memset(&info, 0, sizeof(info));

      info.si_signo = SIGFPE;
      info.si_code = sicode;
      info.si_addr = (void __user *)(instruction_pointer(regs) - 4);

      /*
       * This is the same as NWFPE, because it's not clear what
       * this is used for
       */
      current->thread.error_code = 0;
      current->thread.trap_no = 6;

      send_sig_info(SIGFPE, &info, current);
}

static void vfp_panic(char *reason, u32 inst)
{
      int i;

      printk(KERN_ERR "VFP: Error: %s\n", reason);
      printk(KERN_ERR "VFP: EXC 0x%08x SCR 0x%08x INST 0x%08x\n",
            fmrx(FPEXC), fmrx(FPSCR), inst);
      for (i = 0; i < 32; i += 2)
            printk(KERN_ERR "VFP: s%2u: 0x%08x s%2u: 0x%08x\n",
                   i, vfp_get_float(i), i+1, vfp_get_float(i+1));
}

/*
 * Process bitmask of exception conditions.
 */
static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs)
{
      int si_code = 0;

      pr_debug("VFP: raising exceptions %08x\n", exceptions);

      if (exceptions == VFP_EXCEPTION_ERROR) {
            vfp_panic("unhandled bounce", inst);
            vfp_raise_sigfpe(0, regs);
            return;
      }

      /*
       * If any of the status flags are set, update the FPSCR.
       * Comparison instructions always return at least one of
       * these flags set.
       */
      if (exceptions & (FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V))
            fpscr &= ~(FPSCR_N|FPSCR_Z|FPSCR_C|FPSCR_V);

      fpscr |= exceptions;

      fmxr(FPSCR, fpscr);

#define RAISE(stat,en,sig)                      \
      if (exceptions & stat && fpscr & en)            \
            si_code = sig;

      /*
       * These are arranged in priority order, least to highest.
       */
      RAISE(FPSCR_DZC, FPSCR_DZE, FPE_FLTDIV);
      RAISE(FPSCR_IXC, FPSCR_IXE, FPE_FLTRES);
      RAISE(FPSCR_UFC, FPSCR_UFE, FPE_FLTUND);
      RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF);
      RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV);

      if (si_code)
            vfp_raise_sigfpe(si_code, regs);
}

/*
 * Emulate a VFP instruction.
 */
static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
{
      u32 exceptions = VFP_EXCEPTION_ERROR;

      pr_debug("VFP: emulate: INST=0x%08x SCR=0x%08x\n", inst, fpscr);

      if (INST_CPRTDO(inst)) {
            if (!INST_CPRT(inst)) {
                  /*
                   * CPDO
                   */
                  if (vfp_single(inst)) {
                        exceptions = vfp_single_cpdo(inst, fpscr);
                  } else {
                        exceptions = vfp_double_cpdo(inst, fpscr);
                  }
            } else {
                  /*
                   * A CPRT instruction can not appear in FPINST2, nor
                   * can it cause an exception.  Therefore, we do not
                   * have to emulate it.
                   */
            }
      } else {
            /*
             * A CPDT instruction can not appear in FPINST2, nor can
             * it cause an exception.  Therefore, we do not have to
             * emulate it.
             */
      }
      return exceptions & ~VFP_NAN_FLAG;
}

/*
 * Package up a bounce condition.
 */
void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
{
      u32 fpscr, orig_fpscr, fpsid, exceptions;

      pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc);

      /*
       * At this point, FPEXC can have the following configuration:
       *
       *  EX DEX IXE
       *  0   1   x   - synchronous exception
       *  1   x   0   - asynchronous exception
       *  1   x   1   - sychronous on VFP subarch 1 and asynchronous on later
       *  0   0   1   - synchronous on VFP9 (non-standard subarch 1
       *                implementation), undefined otherwise
       *
       * Clear various bits and enable access to the VFP so we can
       * handle the bounce.
       */
      fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK));

      fpsid = fmrx(FPSID);
      orig_fpscr = fpscr = fmrx(FPSCR);

      /*
       * Check for the special VFP subarch 1 and FPSCR.IXE bit case
       */
      if ((fpsid & FPSID_ARCH_MASK) == (1 << FPSID_ARCH_BIT)
          && (fpscr & FPSCR_IXE)) {
            /*
             * Synchronous exception, emulate the trigger instruction
             */
            goto emulate;
      }

      if (fpexc & FPEXC_EX) {
#ifndef CONFIG_CPU_FEROCEON
            /*
             * Asynchronous exception. The instruction is read from FPINST
             * and the interrupted instruction has to be restarted.
             */
            trigger = fmrx(FPINST);
            regs->ARM_pc -= 4;
#endif
      } else if (!(fpexc & FPEXC_DEX)) {
            /*
             * Illegal combination of bits. It can be caused by an
             * unallocated VFP instruction but with FPSCR.IXE set and not
             * on VFP subarch 1.
             */
             vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs);
            goto exit;
      }

      /*
       * Modify fpscr to indicate the number of iterations remaining.
       * If FPEXC.EX is 0, FPEXC.DEX is 1 and the FPEXC.VV bit indicates
       * whether FPEXC.VECITR or FPSCR.LEN is used.
       */
      if (fpexc & (FPEXC_EX | FPEXC_VV)) {
            u32 len;

            len = fpexc + (1 << FPEXC_LENGTH_BIT);

            fpscr &= ~FPSCR_LENGTH_MASK;
            fpscr |= (len & FPEXC_LENGTH_MASK) << (FPSCR_LENGTH_BIT - FPEXC_LENGTH_BIT);
      }

      /*
       * Handle the first FP instruction.  We used to take note of the
       * FPEXC bounce reason, but this appears to be unreliable.
       * Emulate the bounced instruction instead.
       */
      exceptions = vfp_emulate_instruction(trigger, fpscr, regs);
      if (exceptions)
            vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);

      /*
       * If there isn't a second FP instruction, exit now. Note that
       * the FPEXC.FP2V bit is valid only if FPEXC.EX is 1.
       */
      if (fpexc ^ (FPEXC_EX | FPEXC_FP2V))
            goto exit;

      /*
       * The barrier() here prevents fpinst2 being read
       * before the condition above.
       */
      barrier();
      trigger = fmrx(FPINST2);

 emulate:
      exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs);
      if (exceptions)
            vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
 exit:
      preempt_enable();
}

static void vfp_enable(void *unused)
{
      u32 access = get_copro_access();

      /*
       * Enable full access to VFP (cp10 and cp11)
       */
      set_copro_access(access | CPACC_FULL(10) | CPACC_FULL(11));
}

#ifdef CONFIG_PM
#include <linux/sysdev.h>

static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
{
      struct thread_info *ti = current_thread_info();
      u32 fpexc = fmrx(FPEXC);

      /* if vfp is on, then save state for resumption */
      if (fpexc & FPEXC_EN) {
            printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
            vfp_save_state(&ti->vfpstate, fpexc);

            /* disable, just in case */
            fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
      }

      /* clear any information we had about last context state */
      memset(last_VFP_context, 0, sizeof(last_VFP_context));

      return 0;
}

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;
}

static struct sysdev_class vfp_pm_sysclass = {
      .name       = "vfp",
      .suspend    = vfp_pm_suspend,
      .resume           = vfp_pm_resume,
};

static struct sys_device vfp_pm_sysdev = {
      .cls  = &vfp_pm_sysclass,
};

static void vfp_pm_init(void)
{
      sysdev_class_register(&vfp_pm_sysclass);
      sysdev_register(&vfp_pm_sysdev);
}


#else
static inline void vfp_pm_init(void) { }
#endif /* CONFIG_PM */

void vfp_sync_hwstate(struct thread_info *thread)
{
      unsigned int cpu = get_cpu();

      /*
       * If the thread we're interested in is the current owner of the
       * hardware VFP state, then we need to save its state.
       */
      if (last_VFP_context[cpu] == &thread->vfpstate) {
            u32 fpexc = fmrx(FPEXC);

            /*
             * Save the last VFP state on this CPU.
             */
            fmxr(FPEXC, fpexc | FPEXC_EN);
            vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN);
            fmxr(FPEXC, fpexc);
      }

      put_cpu();
}

void vfp_flush_hwstate(struct thread_info *thread)
{
      unsigned int cpu = get_cpu();

      /*
       * If the thread we're interested in is the current owner of the
       * hardware VFP state, then we need to save its state.
       */
      if (last_VFP_context[cpu] == &thread->vfpstate) {
            u32 fpexc = fmrx(FPEXC);

            fmxr(FPEXC, fpexc & ~FPEXC_EN);

            /*
             * Set the context to NULL to force a reload the next time
             * the thread uses the VFP.
             */
            last_VFP_context[cpu] = NULL;
      }

#ifdef CONFIG_SMP
      /*
       * For SMP we still have to take care of the case where the thread
       * migrates to another CPU and then back to the original CPU on which
       * the last VFP user is still the same thread. Mark the thread VFP
       * state as belonging to a non-existent CPU so that the saved one will
       * be reloaded in the above case.
       */
      thread->vfpstate.hard.cpu = NR_CPUS;
#endif
      put_cpu();
}

/*
 * VFP hardware can lose all context when a CPU goes offline.
 * Safely clear our held state when a CPU has been killed, and
 * re-enable access to VFP when the CPU comes back online.
 *
 * 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;
}

/*
 * 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. CPUs in this configuration
                   * only have 16 x 64bit registers.
                   */
                  if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1)
                        elf_hwcap |= HWCAP_VFPv3D16;
            }
#endif
#ifdef CONFIG_NEON
            /*
             * 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) {
                  if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
                        elf_hwcap |= HWCAP_NEON;
            }
#endif
      }
      return 0;
}

late_initcall(vfp_init);

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