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kernel: arch: introduce k_float_enable()

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This patch introduce new API to enable FPU of thread. This is pair of
existed k_float_disable() API. And also add empty arch_float_enable()
into each architectures that have arch_float_disable(). The arc and
riscv already implemented arch_float_enable() so I do not touch
these implementations.

Motivation: Current Zephyr implementation does not allow to use FPU
on main and other system threads like as work queue. Users need to
create an other thread with K_FP_REGS for floating point programs.
Users can use FPU more easily if they can enable FPU on running
threads.

Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net>
This commit is contained in:
Katsuhiro Suzuki 2021-02-01 15:16:53 +09:00 • committed by Carles Cufí
commit 59903e2934
10 changed files with 93 additions and 34 deletions
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31
include/arch/x86/ia32/arch.h
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@ -396,37 +396,6 @@ static ALWAYS_INLINE unsigned int arch_irq_lock(void)
struct k_thread;
/**
* @brief Enable preservation of floating point context information.
*
* This routine informs the kernel that the specified thread (which may be
* the current thread) will be using the floating point registers.
* The @a options parameter indicates which floating point register sets
* will be used by the specified thread:
*
* - K_FP_REGS indicates x87 FPU and MMX registers only
* - K_SSE_REGS indicates SSE registers (and also x87 FPU and MMX registers)
*
* Invoking this routine initializes the thread's floating point context info
* to that of an FPU that has been reset. The next time the thread is scheduled
* by z_swap() it will either inherit an FPU that is guaranteed to be in a "sane"
* state (if the most recent user of the FPU was cooperatively swapped out)
* or the thread's own floating point context will be loaded (if the most
* recent user of the FPU was preempted, or if this thread is the first user
* of the FPU). Thereafter, the kernel will protect the thread's FP context
* so that it is not altered during a preemptive context switch.
*
* @warning
* This routine should only be used to enable floating point support for a
* thread that does not currently have such support enabled already.
*
* @param thread ID of thread.
* @param options Registers to be preserved (K_FP_REGS or K_SSE_REGS).
*
* @return N/A
*/
extern void k_float_enable(struct k_thread *thread, unsigned int options);
/**
* @}
*/