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181 lines
3.9 KiB
181 lines
3.9 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* linux/arch/arm/kernel/xscale-cp0.c |
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* |
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* XScale DSP and iWMMXt coprocessor context switching and handling |
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*/ |
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#include <linux/types.h> |
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#include <linux/kernel.h> |
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#include <linux/signal.h> |
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#include <linux/sched.h> |
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#include <linux/init.h> |
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#include <linux/io.h> |
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#include <asm/thread_notify.h> |
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#include <asm/cputype.h> |
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asm(" .arch armv5te\n"); |
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static inline void dsp_save_state(u32 *state) |
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{ |
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__asm__ __volatile__ ( |
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"mrrc p0, 0, %0, %1, c0\n" |
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: "=r" (state[0]), "=r" (state[1])); |
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} |
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static inline void dsp_load_state(u32 *state) |
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{ |
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__asm__ __volatile__ ( |
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"mcrr p0, 0, %0, %1, c0\n" |
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: : "r" (state[0]), "r" (state[1])); |
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} |
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static int dsp_do(struct notifier_block *self, unsigned long cmd, void *t) |
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{ |
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struct thread_info *thread = t; |
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switch (cmd) { |
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case THREAD_NOTIFY_FLUSH: |
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thread->cpu_context.extra[0] = 0; |
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thread->cpu_context.extra[1] = 0; |
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break; |
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case THREAD_NOTIFY_SWITCH: |
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dsp_save_state(current_thread_info()->cpu_context.extra); |
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dsp_load_state(thread->cpu_context.extra); |
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break; |
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} |
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return NOTIFY_DONE; |
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} |
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static struct notifier_block dsp_notifier_block = { |
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.notifier_call = dsp_do, |
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}; |
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#ifdef CONFIG_IWMMXT |
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static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t) |
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{ |
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struct thread_info *thread = t; |
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switch (cmd) { |
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case THREAD_NOTIFY_FLUSH: |
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/* |
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* flush_thread() zeroes thread->fpstate, so no need |
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* to do anything here. |
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* |
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* FALLTHROUGH: Ensure we don't try to overwrite our newly |
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* initialised state information on the first fault. |
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*/ |
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case THREAD_NOTIFY_EXIT: |
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iwmmxt_task_release(thread); |
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break; |
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case THREAD_NOTIFY_SWITCH: |
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iwmmxt_task_switch(thread); |
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break; |
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} |
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return NOTIFY_DONE; |
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} |
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static struct notifier_block iwmmxt_notifier_block = { |
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.notifier_call = iwmmxt_do, |
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}; |
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#endif |
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static u32 __init xscale_cp_access_read(void) |
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{ |
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u32 value; |
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__asm__ __volatile__ ( |
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"mrc p15, 0, %0, c15, c1, 0\n\t" |
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: "=r" (value)); |
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return value; |
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} |
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static void __init xscale_cp_access_write(u32 value) |
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{ |
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u32 temp; |
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__asm__ __volatile__ ( |
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"mcr p15, 0, %1, c15, c1, 0\n\t" |
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"mrc p15, 0, %0, c15, c1, 0\n\t" |
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"mov %0, %0\n\t" |
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"sub pc, pc, #4\n\t" |
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: "=r" (temp) : "r" (value)); |
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} |
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/* |
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* Detect whether we have a MAC coprocessor (40 bit register) or an |
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* iWMMXt coprocessor (64 bit registers) by loading 00000100:00000000 |
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* into a coprocessor register and reading it back, and checking |
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* whether the upper word survived intact. |
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*/ |
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static int __init cpu_has_iwmmxt(void) |
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{ |
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u32 lo; |
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u32 hi; |
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/* |
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* This sequence is interpreted by the DSP coprocessor as: |
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* mar acc0, %2, %3 |
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* mra %0, %1, acc0 |
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* |
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* And by the iWMMXt coprocessor as: |
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* tmcrr wR0, %2, %3 |
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* tmrrc %0, %1, wR0 |
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*/ |
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__asm__ __volatile__ ( |
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"mcrr p0, 0, %2, %3, c0\n" |
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"mrrc p0, 0, %0, %1, c0\n" |
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: "=r" (lo), "=r" (hi) |
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: "r" (0), "r" (0x100)); |
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return !!hi; |
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} |
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/* |
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* If we detect that the CPU has iWMMXt (and CONFIG_IWMMXT=y), we |
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* disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy |
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* switch code handle iWMMXt context switching. If on the other |
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* hand the CPU has a DSP coprocessor, we keep access to CP0 enabled |
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* all the time, and save/restore acc0 on context switch in non-lazy |
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* fashion. |
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*/ |
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static int __init xscale_cp0_init(void) |
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{ |
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u32 cp_access; |
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/* do not attempt to probe iwmmxt on non-xscale family CPUs */ |
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if (!cpu_is_xscale_family()) |
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return 0; |
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cp_access = xscale_cp_access_read() & ~3; |
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xscale_cp_access_write(cp_access | 1); |
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if (cpu_has_iwmmxt()) { |
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#ifndef CONFIG_IWMMXT |
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pr_warn("CAUTION: XScale iWMMXt coprocessor detected, but kernel support is missing.\n"); |
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#else |
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pr_info("XScale iWMMXt coprocessor detected.\n"); |
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elf_hwcap |= HWCAP_IWMMXT; |
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thread_register_notifier(&iwmmxt_notifier_block); |
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#endif |
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} else { |
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pr_info("XScale DSP coprocessor detected.\n"); |
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thread_register_notifier(&dsp_notifier_block); |
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cp_access |= 1; |
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} |
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xscale_cp_access_write(cp_access); |
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return 0; |
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} |
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late_initcall(xscale_cp0_init);
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