1/*
2 * Copyright (C) 2019 Collabora, Ltd.
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 * SOFTWARE.
22 *
23 * Authors:
24 *   Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
25 */
26
27#include "util/u_math.h"
28#include "util/macros.h"
29#include "pan_encoder.h"
30
31/* Midgard has a small register file, so shaders with high register pressure
32 * need to spill from the register file onto the stack. In addition to
33 * spilling, it is desireable to allocate temporary arrays on the stack (for
34 * instance because the register file does not support indirect access but the
35 * stack does).
36 *
37 * The stack is located in "Thread Local Storage", sometimes abbreviated TLS in
38 * the kernel source code. Thread local storage is allocated per-thread,
39 * per-core, so threads executing concurrently do not interfere with each
40 * other's stacks. On modern kernels, we may query
41 * DRM_PANFROST_PARAM_THREAD_TLS_ALLOC for the number of threads per core we
42 * must allocate for, and DRM_PANFROST_PARAM_SHADER_PRESENT for a bitmask of
43 * shader cores (so take a popcount of that mask for the number of shader
44 * cores). On older kernels that do not support querying these values,
45 * following kbase, we may use the worst-case value of 256 threads for
46 * THREAD_TLS_ALLOC, and the worst-case value of 16 cores for Midgard per the
47 * "shader core count" column of the implementations table in
48 * https://en.wikipedia.org/wiki/Mali_%28GPU% [citation needed]
49 *
50 * Within a particular thread, there is stack allocated. If it is present, its
51 * size is a power-of-two, and it is at least 16 bytes. Stack is allocated
52 * with the shared memory descriptor used for all shaders within a frame (note
53 * that they don't execute concurrently so it's fine). So, consider the maximum
54 * stack size used by any shader within a job, and then compute (where npot
55 * denotes the next power of two):
56 *
57 *      bytes/thread = npot(max(size, 16))
58 *      allocated = (# of bytes/thread) * (# of threads/core) * (# of cores)
59 *
60 * The size of Thread Local Storage is signaled to the GPU in the tls_size
61 * field, which has a log2 modifier and is in units of 16 bytes.
62 */
63
64/* Computes log_stack_size = log2(ceil(s / 16)) */
65
66unsigned
67panfrost_get_stack_shift(unsigned stack_size)
68{
69        if (stack_size)
70                return util_logbase2_ceil(DIV_ROUND_UP(stack_size, 16));
71        else
72                return 0;
73}
74
75/* Computes the aligned stack size given the shift and thread count. */
76
77unsigned
78panfrost_get_total_stack_size(
79                unsigned thread_size,
80                unsigned threads_per_core,
81                unsigned core_count)
82{
83        unsigned size_per_thread = (thread_size == 0) ? 0 :
84                util_next_power_of_two(ALIGN_POT(thread_size, 16));
85
86        return size_per_thread * threads_per_core * core_count;
87}
88