diff options
Diffstat (limited to 'arch/arm/kernel/xscale-cp0.c')
| -rw-r--r-- | arch/arm/kernel/xscale-cp0.c | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/arch/arm/kernel/xscale-cp0.c b/arch/arm/kernel/xscale-cp0.c new file mode 100644 index 0000000000..00d00d3aae --- /dev/null +++ b/arch/arm/kernel/xscale-cp0.c @@ -0,0 +1,182 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/arch/arm/kernel/xscale-cp0.c + * + * XScale DSP and iWMMXt coprocessor context switching and handling + */ + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/signal.h> +#include <linux/sched.h> +#include <linux/init.h> +#include <linux/io.h> +#include <asm/thread_notify.h> +#include <asm/cputype.h> + +asm(" .arch armv5te\n"); + +static inline void dsp_save_state(u32 *state) +{ + __asm__ __volatile__ ( + "mrrc p0, 0, %0, %1, c0\n" + : "=r" (state[0]), "=r" (state[1])); +} + +static inline void dsp_load_state(u32 *state) +{ + __asm__ __volatile__ ( + "mcrr p0, 0, %0, %1, c0\n" + : : "r" (state[0]), "r" (state[1])); +} + +static int dsp_do(struct notifier_block *self, unsigned long cmd, void *t) +{ + struct thread_info *thread = t; + + switch (cmd) { + case THREAD_NOTIFY_FLUSH: + thread->cpu_context.extra[0] = 0; + thread->cpu_context.extra[1] = 0; + break; + + case THREAD_NOTIFY_SWITCH: + dsp_save_state(current_thread_info()->cpu_context.extra); + dsp_load_state(thread->cpu_context.extra); + break; + } + + return NOTIFY_DONE; +} + +static struct notifier_block dsp_notifier_block = { + .notifier_call = dsp_do, +}; + + +#ifdef CONFIG_IWMMXT +static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t) +{ + struct thread_info *thread = t; + + switch (cmd) { + case THREAD_NOTIFY_FLUSH: + /* + * flush_thread() zeroes thread->fpstate, so no need + * to do anything here. + * + * FALLTHROUGH: Ensure we don't try to overwrite our newly + * initialised state information on the first fault. + */ + + case THREAD_NOTIFY_EXIT: + iwmmxt_task_release(thread); + break; + + case THREAD_NOTIFY_SWITCH: + iwmmxt_task_switch(thread); + break; + } + + return NOTIFY_DONE; +} + +static struct notifier_block iwmmxt_notifier_block = { + .notifier_call = iwmmxt_do, +}; +#endif + + +static u32 __init xscale_cp_access_read(void) +{ + u32 value; + + __asm__ __volatile__ ( + "mrc p15, 0, %0, c15, c1, 0\n\t" + : "=r" (value)); + + return value; +} + +static void __init xscale_cp_access_write(u32 value) +{ + u32 temp; + + __asm__ __volatile__ ( + "mcr p15, 0, %1, c15, c1, 0\n\t" + "mrc p15, 0, %0, c15, c1, 0\n\t" + "mov %0, %0\n\t" + "sub pc, pc, #4\n\t" + : "=r" (temp) : "r" (value)); +} + +/* + * Detect whether we have a MAC coprocessor (40 bit register) or an + * iWMMXt coprocessor (64 bit registers) by loading 00000100:00000000 + * into a coprocessor register and reading it back, and checking + * whether the upper word survived intact. + */ +static int __init cpu_has_iwmmxt(void) +{ + u32 lo; + u32 hi; + + /* + * This sequence is interpreted by the DSP coprocessor as: + * mar acc0, %2, %3 + * mra %0, %1, acc0 + * + * And by the iWMMXt coprocessor as: + * tmcrr wR0, %2, %3 + * tmrrc %0, %1, wR0 + */ + __asm__ __volatile__ ( + "mcrr p0, 0, %2, %3, c0\n" + "mrrc p0, 0, %0, %1, c0\n" + : "=r" (lo), "=r" (hi) + : "r" (0), "r" (0x100)); + + return !!hi; +} + + +/* + * If we detect that the CPU has iWMMXt (and CONFIG_IWMMXT=y), we + * disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy + * switch code handle iWMMXt context switching. If on the other + * hand the CPU has a DSP coprocessor, we keep access to CP0 enabled + * all the time, and save/restore acc0 on context switch in non-lazy + * fashion. + */ +static int __init xscale_cp0_init(void) +{ + u32 cp_access; + + /* do not attempt to probe iwmmxt on non-xscale family CPUs */ + if (!cpu_is_xscale_family()) + return 0; + + cp_access = xscale_cp_access_read() & ~3; + xscale_cp_access_write(cp_access | 1); + + if (cpu_has_iwmmxt()) { +#ifndef CONFIG_IWMMXT + pr_warn("CAUTION: XScale iWMMXt coprocessor detected, but kernel support is missing.\n"); +#else + pr_info("XScale iWMMXt coprocessor detected.\n"); + elf_hwcap |= HWCAP_IWMMXT; + thread_register_notifier(&iwmmxt_notifier_block); + register_iwmmxt_undef_handler(); +#endif + } else { + pr_info("XScale DSP coprocessor detected.\n"); + thread_register_notifier(&dsp_notifier_block); + cp_access |= 1; + } + + xscale_cp_access_write(cp_access); + + return 0; +} + +late_initcall(xscale_cp0_init); |