1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
From 1cff637824f8e5626a754cbbb97bc8f3730a88f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
Date: Thu, 1 Jul 2021 19:07:48 +0200
Subject: [PATCH] drm/gud: Use scatter-gather USB bulk transfer
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
[ drm-misc commit 2eecd93b743b5611cd3654698794b4d0cefdc9ee ]
There'a limit to how big a kmalloc buffer can be, and as memory gets
fragmented it becomes more difficult to get big buffers. The downside of
smaller buffers is that the driver has to split the transfer up which
hampers performance. Compression might also take a hit because of the
splitting.
Solve this by allocating the transfer buffer using vmalloc and create a
SG table to be passed on to the USB subsystem. vmalloc_32() is used to
avoid DMA bounce buffers on USB controllers that can only access 32-bit
addresses.
This also solves the problem that split transfers can give host side
tearing since flushing is decoupled from rendering.
usb_sg_wait() doesn't have timeout handling builtin, so it is wrapped in
a timer like 4 out of 6 users in the kernel have done.
v2:
- Use DIV_ROUND_UP (Linus)
- Add timeout note to the commit log (Linus)
- Expand note about upper buffer limit (Linus)
- Change var name s/timer/ctx/ in gud_usb_bulk_timeout()
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210701170748.58009-2-noralf@tronnes.org
---
drivers/gpu/drm/gud/gud_drv.c | 50 +++++++++++++++++++++---------
drivers/gpu/drm/gud/gud_internal.h | 2 ++
drivers/gpu/drm/gud/gud_pipe.c | 47 ++++++++++++++++++++++++----
3 files changed, 78 insertions(+), 21 deletions(-)
--- a/drivers/gpu/drm/gud/gud_drv.c
+++ b/drivers/gpu/drm/gud/gud_drv.c
@@ -407,13 +407,40 @@ static struct drm_driver gud_drm_driver
.minor = 0,
};
+static int gud_alloc_bulk_buffer(struct gud_device *gdrm)
+{
+ unsigned int i, num_pages;
+ struct page **pages;
+ void *ptr;
+ int ret;
+
+ gdrm->bulk_buf = vmalloc_32(gdrm->bulk_len);
+ if (!gdrm->bulk_buf)
+ return -ENOMEM;
+
+ num_pages = DIV_ROUND_UP(gdrm->bulk_len, PAGE_SIZE);
+ pages = kmalloc_array(num_pages, sizeof(struct page *), GFP_KERNEL);
+ if (!pages)
+ return -ENOMEM;
+
+ for (i = 0, ptr = gdrm->bulk_buf; i < num_pages; i++, ptr += PAGE_SIZE)
+ pages[i] = vmalloc_to_page(ptr);
+
+ ret = sg_alloc_table_from_pages(&gdrm->bulk_sgt, pages, num_pages,
+ 0, gdrm->bulk_len, GFP_KERNEL);
+ kfree(pages);
+
+ return ret;
+}
+
static void gud_free_buffers_and_mutex(void *data)
{
struct gud_device *gdrm = data;
vfree(gdrm->compress_buf);
gdrm->compress_buf = NULL;
- kfree(gdrm->bulk_buf);
+ sg_free_table(&gdrm->bulk_sgt);
+ vfree(gdrm->bulk_buf);
gdrm->bulk_buf = NULL;
mutex_destroy(&gdrm->ctrl_lock);
}
@@ -550,24 +577,17 @@ static int gud_probe(struct usb_interfac
if (desc.max_buffer_size)
max_buffer_size = le32_to_cpu(desc.max_buffer_size);
-retry:
- /*
- * Use plain kmalloc here since devm_kmalloc() places struct devres at the beginning
- * of the buffer it allocates. This wastes a lot of memory when allocating big buffers.
- * Asking for 2M would actually allocate 4M. This would also prevent getting the biggest
- * possible buffer potentially leading to split transfers.
- */
- gdrm->bulk_buf = kmalloc(max_buffer_size, GFP_KERNEL | __GFP_NOWARN);
- if (!gdrm->bulk_buf) {
- max_buffer_size = roundup_pow_of_two(max_buffer_size) / 2;
- if (max_buffer_size < SZ_512K)
- return -ENOMEM;
- goto retry;
- }
+ /* Prevent a misbehaving device from allocating loads of RAM. 4096x4096@XRGB8888 = 64 MB */
+ if (max_buffer_size > SZ_64M)
+ max_buffer_size = SZ_64M;
gdrm->bulk_pipe = usb_sndbulkpipe(interface_to_usbdev(intf), usb_endpoint_num(bulk_out));
gdrm->bulk_len = max_buffer_size;
+ ret = gud_alloc_bulk_buffer(gdrm);
+ if (ret)
+ return ret;
+
if (gdrm->compression & GUD_COMPRESSION_LZ4) {
gdrm->lz4_comp_mem = devm_kmalloc(dev, LZ4_MEM_COMPRESS, GFP_KERNEL);
if (!gdrm->lz4_comp_mem)
--- a/drivers/gpu/drm/gud/gud_internal.h
+++ b/drivers/gpu/drm/gud/gud_internal.h
@@ -5,6 +5,7 @@
#include <linux/list.h>
#include <linux/mutex.h>
+#include <linux/scatterlist.h>
#include <linux/usb.h>
#include <linux/workqueue.h>
#include <uapi/drm/drm_fourcc.h>
@@ -26,6 +27,7 @@ struct gud_device {
unsigned int bulk_pipe;
void *bulk_buf;
size_t bulk_len;
+ struct sg_table bulk_sgt;
u8 compression;
void *lz4_comp_mem;
--- a/drivers/gpu/drm/gud/gud_pipe.c
+++ b/drivers/gpu/drm/gud/gud_pipe.c
@@ -219,13 +219,51 @@ vunmap:
return ret;
}
+struct gud_usb_bulk_context {
+ struct timer_list timer;
+ struct usb_sg_request sgr;
+};
+
+static void gud_usb_bulk_timeout(struct timer_list *t)
+{
+ struct gud_usb_bulk_context *ctx = from_timer(ctx, t, timer);
+
+ usb_sg_cancel(&ctx->sgr);
+}
+
+static int gud_usb_bulk(struct gud_device *gdrm, size_t len)
+{
+ struct gud_usb_bulk_context ctx;
+ int ret;
+
+ ret = usb_sg_init(&ctx.sgr, gud_to_usb_device(gdrm), gdrm->bulk_pipe, 0,
+ gdrm->bulk_sgt.sgl, gdrm->bulk_sgt.nents, len, GFP_KERNEL);
+ if (ret)
+ return ret;
+
+ timer_setup_on_stack(&ctx.timer, gud_usb_bulk_timeout, 0);
+ mod_timer(&ctx.timer, jiffies + msecs_to_jiffies(3000));
+
+ usb_sg_wait(&ctx.sgr);
+
+ if (!del_timer_sync(&ctx.timer))
+ ret = -ETIMEDOUT;
+ else if (ctx.sgr.status < 0)
+ ret = ctx.sgr.status;
+ else if (ctx.sgr.bytes != len)
+ ret = -EIO;
+
+ destroy_timer_on_stack(&ctx.timer);
+
+ return ret;
+}
+
static int gud_flush_rect(struct gud_device *gdrm, struct drm_framebuffer *fb,
const struct drm_format_info *format, struct drm_rect *rect)
{
- struct usb_device *usb = gud_to_usb_device(gdrm);
struct gud_set_buffer_req req;
- int ret, actual_length;
size_t len, trlen;
+ int ret;
drm_dbg(&gdrm->drm, "Flushing [FB:%d] " DRM_RECT_FMT "\n", fb->base.id, DRM_RECT_ARG(rect));
@@ -254,10 +292,7 @@ static int gud_flush_rect(struct gud_dev
return ret;
}
- ret = usb_bulk_msg(usb, gdrm->bulk_pipe, gdrm->bulk_buf, trlen,
- &actual_length, msecs_to_jiffies(3000));
- if (!ret && trlen != actual_length)
- ret = -EIO;
+ ret = gud_usb_bulk(gdrm, trlen);
if (ret)
gdrm->stats_num_errors++;
|
