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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 <roberto@unbit.it>
5 * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
6 * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>
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
43static 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
78static inline u16 pixel32_to_be16(const uint32_t pixel)
79{
80 return (((pixel >> 3) & 0x001f) |
81 ((pixel >> 5) & 0x07e0) |
82 ((pixel >> 8) & 0xf800));
83}
84
85static bool pixel_repeats(const void *pixel, const uint32_t repeat, int bpp)
86{
87 if (bpp == 2)
88 return *(const uint16_t *)pixel == repeat;
89 else
90 return *(const uint32_t *)pixel == repeat;
91}
92
93/*
94 * Render a command stream for an encoded horizontal line segment of pixels.
95 *
96 * A command buffer holds several commands.
97 * It always begins with a fresh command header
98 * (the protocol doesn't require this, but we enforce it to allow
99 * multiple buffers to be potentially encoded and sent in parallel).
100 * A single command encodes one contiguous horizontal line of pixels
101 *
102 * The function relies on the client to do all allocation, so that
103 * rendering can be done directly to output buffers (e.g. USB URBs).
104 * The function fills the supplied command buffer, providing information
105 * on where it left off, so the client may call in again with additional
106 * buffers if the line will take several buffers to complete.
107 *
108 * A single command can transmit a maximum of 256 pixels,
109 * regardless of the compression ratio (protocol design limit).
110 * To the hardware, 0 for a size byte means 256
111 *
112 * Rather than 256 pixel commands which are either rl or raw encoded,
113 * the rlx command simply assumes alternating raw and rl spans within one cmd.
114 * This has a slightly larger header overhead, but produces more even results.
115 * It also processes all data (read and write) in a single pass.
116 * Performance benchmarks of common cases show it having just slightly better
117 * compression than 256 pixel raw or rle commands, with similar CPU consumpion.
118 * But for very rl friendly data, will compress not quite as well.
119 */
120static void udl_compress_hline16(
121 const u8 **pixel_start_ptr,
122 const u8 *const pixel_end,
123 uint32_t *device_address_ptr,
124 uint8_t **command_buffer_ptr,
125 const uint8_t *const cmd_buffer_end, int bpp)
126{
127 const u8 *pixel = *pixel_start_ptr;
128 uint32_t dev_addr = *device_address_ptr;
129 uint8_t *cmd = *command_buffer_ptr;
130
131 while ((pixel_end > pixel) &&
132 (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
133 uint8_t *raw_pixels_count_byte = NULL;
134 uint8_t *cmd_pixels_count_byte = NULL;
135 const u8 *raw_pixel_start = NULL;
136 const u8 *cmd_pixel_start, *cmd_pixel_end = NULL;
137
138 prefetchw((void *) cmd); /* pull in one cache line at least */
139
140 *cmd++ = 0xaf;
141 *cmd++ = 0x6b;
142 *cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
143 *cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
144 *cmd++ = (uint8_t) ((dev_addr) & 0xFF);
145
146 cmd_pixels_count_byte = cmd++; /* we'll know this later */
147 cmd_pixel_start = pixel;
148
149 raw_pixels_count_byte = cmd++; /* we'll know this later */
150 raw_pixel_start = pixel;
151
152 cmd_pixel_end = pixel + (min(MAX_CMD_PIXELS + 1,
153 min((int)(pixel_end - pixel) / bpp,
154 (int)(cmd_buffer_end - cmd) / 2))) * bpp;
155
156 prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
157
158 while (pixel < cmd_pixel_end) {
159 const u8 *const start = pixel;
160 u32 repeating_pixel;
161
162 if (bpp == 2) {
163 repeating_pixel = *(uint16_t *)pixel;
164 *(uint16_t *)cmd = cpu_to_be16(repeating_pixel);
165 } else {
166 repeating_pixel = *(uint32_t *)pixel;
167 *(uint16_t *)cmd = cpu_to_be16(pixel32_to_be16(repeating_pixel));
168 }
169
170 cmd += 2;
171 pixel += bpp;
172
173 if (unlikely((pixel < cmd_pixel_end) &&
174 (pixel_repeats(pixel, repeating_pixel, bpp)))) {
175 /* go back and fill in raw pixel count */
176 *raw_pixels_count_byte = (((start -
177 raw_pixel_start) / bpp) + 1) & 0xFF;
178
179 while ((pixel < cmd_pixel_end) &&
180 (pixel_repeats(pixel, repeating_pixel, bpp))) {
181 pixel += bpp;
182 }
183
184 /* immediately after raw data is repeat byte */
185 *cmd++ = (((pixel - start) / bpp) - 1) & 0xFF;
186
187 /* Then start another raw pixel span */
188 raw_pixel_start = pixel;
189 raw_pixels_count_byte = cmd++;
190 }
191 }
192
193 if (pixel > raw_pixel_start) {
194 /* finalize last RAW span */
195 *raw_pixels_count_byte = ((pixel-raw_pixel_start) / bpp) & 0xFF;
196 }
197
198 *cmd_pixels_count_byte = ((pixel - cmd_pixel_start) / bpp) & 0xFF;
199 dev_addr += ((pixel - cmd_pixel_start) / bpp) * 2;
200 }
201
202 if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
203 /* Fill leftover bytes with no-ops */
204 if (cmd_buffer_end > cmd)
205 memset(cmd, 0xAF, cmd_buffer_end - cmd);
206 cmd = (uint8_t *) cmd_buffer_end;
207 }
208
209 *command_buffer_ptr = cmd;
210 *pixel_start_ptr = pixel;
211 *device_address_ptr = dev_addr;
212
213 return;
214}
215
216/*
217 * There are 3 copies of every pixel: The front buffer that the fbdev
218 * client renders to, the actual framebuffer across the USB bus in hardware
219 * (that we can only write to, slowly, and can never read), and (optionally)
220 * our shadow copy that tracks what's been sent to that hardware buffer.
221 */
222int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
223 const char *front, char **urb_buf_ptr,
224 u32 byte_offset, u32 device_byte_offset,
225 u32 byte_width,
226 int *ident_ptr, int *sent_ptr)
227{
228 const u8 *line_start, *line_end, *next_pixel;
229 u32 base16 = 0 + (device_byte_offset / bpp) * 2;
230 struct urb *urb = *urb_ptr;
231 u8 *cmd = *urb_buf_ptr;
232 u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
233
234 BUG_ON(!(bpp == 2 || bpp == 4));
235
236 line_start = (u8 *) (front + byte_offset);
237 next_pixel = line_start;
238 line_end = next_pixel + byte_width;
239
240 while (next_pixel < line_end) {
241
242 udl_compress_hline16(&next_pixel,
243 line_end, &base16,
244 (u8 **) &cmd, (u8 *) cmd_end, bpp);
245
246 if (cmd >= cmd_end) {
247 int len = cmd - (u8 *) urb->transfer_buffer;
248 if (udl_submit_urb(dev, urb, len))
249 return 1; /* lost pixels is set */
250 *sent_ptr += len;
251 urb = udl_get_urb(dev);
252 if (!urb)
253 return 1; /* lost_pixels is set */
254 *urb_ptr = urb;
255 cmd = urb->transfer_buffer;
256 cmd_end = &cmd[urb->transfer_buffer_length];
257 }
258 }
259
260 *urb_buf_ptr = cmd;
261
262 return 0;
263}
264