drivers/gpu/drm/udl/udl_transfer.c

   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 "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 = 0;
 130                 uint8_t *cmd_pixels_count_byte = 0;
 131                 const u8 *raw_pixel_start = 0;
 132                 const u8 *cmd_pixel_start, *cmd_pixel_end = 0;
 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 byte_width,
 217                      int *ident_ptr, int *sent_ptr)
 218 {
 219         const u8 *line_start, *line_end, *next_pixel;
 220         u32 base16 = 0 + (byte_offset / bpp) * 2;
 221         struct urb *urb = *urb_ptr;
 222         u8 *cmd = *urb_buf_ptr;
 223         u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
 224
 225         line_start = (u8 *) (front + byte_offset);
 226         next_pixel = line_start;
 227         line_end = next_pixel + byte_width;
 228
 229         while (next_pixel < line_end) {
 230
 231                 udl_compress_hline16(&next_pixel,
 232                              line_end, &base16,
 233                              (u8 **) &cmd, (u8 *) cmd_end, bpp);
 234
 235                 if (cmd >= cmd_end) {
 236                         int len = cmd - (u8 *) urb->transfer_buffer;
 237                         if (udl_submit_urb(dev, urb, len))
 238                                 return 1; /* lost pixels is set */
 239                         *sent_ptr += len;
 240                         urb = udl_get_urb(dev);
 241                         if (!urb)
 242                                 return 1; /* lost_pixels is set */
 243                         *urb_ptr = urb;
 244                         cmd = urb->transfer_buffer;
 245                         cmd_end = &cmd[urb->transfer_buffer_length];
 246                 }
 247         }
 248
 249         *urb_buf_ptr = cmd;
 250
 251         return 0;
 252 }
 253