drivers/gpu/drm/i915/i915_memcpy.c

/*
 * Copyright © 2016 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 */

#include <linux/kernel.h>
#include <asm/fpu/api.h>

#include "i915_drv.h"

static DEFINE_STATIC_KEY_FALSE(has_movntdqa);

#ifdef CONFIG_AS_MOVNTDQA
static void __memcpy_ntdqa(void *dst, const void *src, unsigned long len)
{
	kernel_fpu_begin();

	len >>= 4;
	while (len >= 4) {
		asm("movntdqa   (%0), %%xmm0\n"
		    "movntdqa 16(%0), %%xmm1\n"
		    "movntdqa 32(%0), %%xmm2\n"
		    "movntdqa 48(%0), %%xmm3\n"
		    "movaps %%xmm0,   (%1)\n"
		    "movaps %%xmm1, 16(%1)\n"
		    "movaps %%xmm2, 32(%1)\n"
		    "movaps %%xmm3, 48(%1)\n"
		    :: "r" (src), "r" (dst) : "memory");
		src += 64;
		dst += 64;
		len -= 4;
	}
	while (len--) {
		asm("movntdqa (%0), %%xmm0\n"
		    "movaps %%xmm0, (%1)\n"
		    :: "r" (src), "r" (dst) : "memory");
		src += 16;
		dst += 16;
	}

	kernel_fpu_end();
}
#endif

/**
 * i915_memcpy_from_wc: perform an accelerated *aligned* read from WC
 * @dst: destination pointer
 * @src: source pointer
 * @len: how many bytes to copy
 *
 * i915_memcpy_from_wc copies @len bytes from @src to @dst using
 * non-temporal instructions where available. Note that all arguments
 * (@src, @dst) must be aligned to 16 bytes and @len must be a multiple
 * of 16.
 *
 * To test whether accelerated reads from WC are supported, use
 * i915_memcpy_from_wc(NULL, NULL, 0);
 *
 * Returns true if the copy was successful, false if the preconditions
 * are not met.
 */
bool i915_memcpy_from_wc(void *dst, const void *src, unsigned long len)
{
	if (unlikely(((unsigned long)dst | (unsigned long)src | len) & 15))
		return false;

#ifdef CONFIG_AS_MOVNTDQA
	if (static_branch_likely(&has_movntdqa)) {
		if (likely(len))
			__memcpy_ntdqa(dst, src, len);
		return true;
	}
#endif

	return false;
}

void i915_memcpy_init_early(struct drm_i915_private *dev_priv)
{
	if (static_cpu_has(X86_FEATURE_XMM4_1))
		static_branch_enable(&has_movntdqa);
}