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udl_transfer.c
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1 /*
2  * Copyright (C) 2012 Red Hat
3  * based in parts on udlfb.c:
4  * Copyright (C) 2009 Roberto De Ioris <[email protected]>
5  * Copyright (C) 2009 Jaya Kumar <[email protected]>
6  * Copyright (C) 2009 Bernie Thompson <[email protected]>
7  *
8  * This file is subject to the terms and conditions of the GNU General Public
9  * License v2. See the file COPYING in the main directory of this archive for
10  * more details.
11  */
12 
13 #include <linux/module.h>
14 #include <linux/slab.h>
15 #include <linux/fb.h>
16 #include <linux/prefetch.h>
17 
18 #include <drm/drmP.h>
19 #include "udl_drv.h"
20 
21 #define MAX_CMD_PIXELS 255
22 
23 #define RLX_HEADER_BYTES 7
24 #define MIN_RLX_PIX_BYTES 4
25 #define MIN_RLX_CMD_BYTES (RLX_HEADER_BYTES + MIN_RLX_PIX_BYTES)
26 
27 #define RLE_HEADER_BYTES 6
28 #define MIN_RLE_PIX_BYTES 3
29 #define MIN_RLE_CMD_BYTES (RLE_HEADER_BYTES + MIN_RLE_PIX_BYTES)
30 
31 #define RAW_HEADER_BYTES 6
32 #define MIN_RAW_PIX_BYTES 2
33 #define MIN_RAW_CMD_BYTES (RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)
34 
35 /*
36  * Trims identical data from front and back of line
37  * Sets new front buffer address and width
38  * And returns byte count of identical pixels
39  * Assumes CPU natural alignment (unsigned long)
40  * for back and front buffer ptrs and width
41  */
42 #if 0
43 static int udl_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)
44 {
45  int j, k;
46  const unsigned long *back = (const unsigned long *) bback;
47  const unsigned long *front = (const unsigned long *) *bfront;
48  const int width = *width_bytes / sizeof(unsigned long);
49  int identical = width;
50  int start = width;
51  int end = width;
52 
53  prefetch((void *) front);
54  prefetch((void *) back);
55 
56  for (j = 0; j < width; j++) {
57  if (back[j] != front[j]) {
58  start = j;
59  break;
60  }
61  }
62 
63  for (k = width - 1; k > j; k--) {
64  if (back[k] != front[k]) {
65  end = k+1;
66  break;
67  }
68  }
69 
70  identical = start + (width - end);
71  *bfront = (u8 *) &front[start];
72  *width_bytes = (end - start) * sizeof(unsigned long);
73 
74  return identical * sizeof(unsigned long);
75 }
76 #endif
77 
78 static inline u16 pixel32_to_be16p(const uint8_t *pixel)
79 {
80  uint32_t pix = *(uint32_t *)pixel;
81  u16 retval;
82 
83  retval = (((pix >> 3) & 0x001f) |
84  ((pix >> 5) & 0x07e0) |
85  ((pix >> 8) & 0xf800));
86  return retval;
87 }
88 
89 /*
90  * Render a command stream for an encoded horizontal line segment of pixels.
91  *
92  * A command buffer holds several commands.
93  * It always begins with a fresh command header
94  * (the protocol doesn't require this, but we enforce it to allow
95  * multiple buffers to be potentially encoded and sent in parallel).
96  * A single command encodes one contiguous horizontal line of pixels
97  *
98  * The function relies on the client to do all allocation, so that
99  * rendering can be done directly to output buffers (e.g. USB URBs).
100  * The function fills the supplied command buffer, providing information
101  * on where it left off, so the client may call in again with additional
102  * buffers if the line will take several buffers to complete.
103  *
104  * A single command can transmit a maximum of 256 pixels,
105  * regardless of the compression ratio (protocol design limit).
106  * To the hardware, 0 for a size byte means 256
107  *
108  * Rather than 256 pixel commands which are either rl or raw encoded,
109  * the rlx command simply assumes alternating raw and rl spans within one cmd.
110  * This has a slightly larger header overhead, but produces more even results.
111  * It also processes all data (read and write) in a single pass.
112  * Performance benchmarks of common cases show it having just slightly better
113  * compression than 256 pixel raw or rle commands, with similar CPU consumpion.
114  * But for very rl friendly data, will compress not quite as well.
115  */
116 static void udl_compress_hline16(
117  const u8 **pixel_start_ptr,
118  const u8 *const pixel_end,
119  uint32_t *device_address_ptr,
120  uint8_t **command_buffer_ptr,
121  const uint8_t *const cmd_buffer_end, int bpp)
122 {
123  const u8 *pixel = *pixel_start_ptr;
124  uint32_t dev_addr = *device_address_ptr;
125  uint8_t *cmd = *command_buffer_ptr;
126 
127  while ((pixel_end > pixel) &&
128  (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
129  uint8_t *raw_pixels_count_byte = NULL;
130  uint8_t *cmd_pixels_count_byte = NULL;
131  const u8 *raw_pixel_start = NULL;
132  const u8 *cmd_pixel_start, *cmd_pixel_end = NULL;
133 
134  prefetchw((void *) cmd); /* pull in one cache line at least */
135 
136  *cmd++ = 0xaf;
137  *cmd++ = 0x6b;
138  *cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
139  *cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
140  *cmd++ = (uint8_t) ((dev_addr) & 0xFF);
141 
142  cmd_pixels_count_byte = cmd++; /* we'll know this later */
143  cmd_pixel_start = pixel;
144 
145  raw_pixels_count_byte = cmd++; /* we'll know this later */
146  raw_pixel_start = pixel;
147 
148  cmd_pixel_end = pixel + (min(MAX_CMD_PIXELS + 1,
149  min((int)(pixel_end - pixel) / bpp,
150  (int)(cmd_buffer_end - cmd) / 2))) * bpp;
151 
152  prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
153 
154  while (pixel < cmd_pixel_end) {
155  const u8 * const repeating_pixel = pixel;
156 
157  if (bpp == 2)
158  *(uint16_t *)cmd = cpu_to_be16p((uint16_t *)pixel);
159  else if (bpp == 4)
160  *(uint16_t *)cmd = cpu_to_be16(pixel32_to_be16p(pixel));
161 
162  cmd += 2;
163  pixel += bpp;
164 
165  if (unlikely((pixel < cmd_pixel_end) &&
166  (!memcmp(pixel, repeating_pixel, bpp)))) {
167  /* go back and fill in raw pixel count */
168  *raw_pixels_count_byte = (((repeating_pixel -
169  raw_pixel_start) / bpp) + 1) & 0xFF;
170 
171  while ((pixel < cmd_pixel_end)
172  && (!memcmp(pixel, repeating_pixel, bpp))) {
173  pixel += bpp;
174  }
175 
176  /* immediately after raw data is repeat byte */
177  *cmd++ = (((pixel - repeating_pixel) / bpp) - 1) & 0xFF;
178 
179  /* Then start another raw pixel span */
180  raw_pixel_start = pixel;
181  raw_pixels_count_byte = cmd++;
182  }
183  }
184 
185  if (pixel > raw_pixel_start) {
186  /* finalize last RAW span */
187  *raw_pixels_count_byte = ((pixel-raw_pixel_start) / bpp) & 0xFF;
188  }
189 
190  *cmd_pixels_count_byte = ((pixel - cmd_pixel_start) / bpp) & 0xFF;
191  dev_addr += ((pixel - cmd_pixel_start) / bpp) * 2;
192  }
193 
194  if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
195  /* Fill leftover bytes with no-ops */
196  if (cmd_buffer_end > cmd)
197  memset(cmd, 0xAF, cmd_buffer_end - cmd);
198  cmd = (uint8_t *) cmd_buffer_end;
199  }
200 
201  *command_buffer_ptr = cmd;
202  *pixel_start_ptr = pixel;
203  *device_address_ptr = dev_addr;
204 
205  return;
206 }
207 
208 /*
209  * There are 3 copies of every pixel: The front buffer that the fbdev
210  * client renders to, the actual framebuffer across the USB bus in hardware
211  * (that we can only write to, slowly, and can never read), and (optionally)
212  * our shadow copy that tracks what's been sent to that hardware buffer.
213  */
214 int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
215  const char *front, char **urb_buf_ptr,
216  u32 byte_offset, u32 device_byte_offset,
217  u32 byte_width,
218  int *ident_ptr, int *sent_ptr)
219 {
220  const u8 *line_start, *line_end, *next_pixel;
221  u32 base16 = 0 + (device_byte_offset / bpp) * 2;
222  struct urb *urb = *urb_ptr;
223  u8 *cmd = *urb_buf_ptr;
224  u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
225 
226  line_start = (u8 *) (front + byte_offset);
227  next_pixel = line_start;
228  line_end = next_pixel + byte_width;
229 
230  while (next_pixel < line_end) {
231 
232  udl_compress_hline16(&next_pixel,
233  line_end, &base16,
234  (u8 **) &cmd, (u8 *) cmd_end, bpp);
235 
236  if (cmd >= cmd_end) {
237  int len = cmd - (u8 *) urb->transfer_buffer;
238  if (udl_submit_urb(dev, urb, len))
239  return 1; /* lost pixels is set */
240  *sent_ptr += len;
241  urb = udl_get_urb(dev);
242  if (!urb)
243  return 1; /* lost_pixels is set */
244  *urb_ptr = urb;
245  cmd = urb->transfer_buffer;
246  cmd_end = &cmd[urb->transfer_buffer_length];
247  }
248  }
249 
250  *urb_buf_ptr = cmd;
251 
252  return 0;
253 }
254