root/drivers/gpu/drm/udl/udl_transfer.c

DEFINITIONS

1. udl_trim_hline
2. pixel32_to_be16
3. get_pixel_val16
4. udl_compress_hline16
5. udl_render_hline

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2012 Red Hat
   4  * based in parts on udlfb.c:
   5  * Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
   6  * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
   7  * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>
   8  */
   9 
  10 #include <asm/unaligned.h>
  11 
  12 #include "udl_drv.h"
  13 
  14 #define MAX_CMD_PIXELS          255
  15 
  16 #define RLX_HEADER_BYTES        7
  17 #define MIN_RLX_PIX_BYTES       4
  18 #define MIN_RLX_CMD_BYTES       (RLX_HEADER_BYTES + MIN_RLX_PIX_BYTES)
  19 
  20 #define RLE_HEADER_BYTES        6
  21 #define MIN_RLE_PIX_BYTES       3
  22 #define MIN_RLE_CMD_BYTES       (RLE_HEADER_BYTES + MIN_RLE_PIX_BYTES)
  23 
  24 #define RAW_HEADER_BYTES        6
  25 #define MIN_RAW_PIX_BYTES       2
  26 #define MIN_RAW_CMD_BYTES       (RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)
  27 
  28 /*
  29  * Trims identical data from front and back of line
  30  * Sets new front buffer address and width
  31  * And returns byte count of identical pixels
  32  * Assumes CPU natural alignment (unsigned long)
  33  * for back and front buffer ptrs and width
  34  */
  35 #if 0
  36 static int udl_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)
  37 {
  38         int j, k;
  39         const unsigned long *back = (const unsigned long *) bback;
  40         const unsigned long *front = (const unsigned long *) *bfront;
  41         const int width = *width_bytes / sizeof(unsigned long);
  42         int identical = width;
  43         int start = width;
  44         int end = width;
  45 
  46         for (j = 0; j < width; j++) {
  47                 if (back[j] != front[j]) {
  48                         start = j;
  49                         break;
  50                 }
  51         }
  52 
  53         for (k = width - 1; k > j; k--) {
  54                 if (back[k] != front[k]) {
  55                         end = k+1;
  56                         break;
  57                 }
  58         }
  59 
  60         identical = start + (width - end);
  61         *bfront = (u8 *) &front[start];
  62         *width_bytes = (end - start) * sizeof(unsigned long);
  63 
  64         return identical * sizeof(unsigned long);
  65 }
  66 #endif
  67 
  68 static inline u16 pixel32_to_be16(const uint32_t pixel)
  69 {
  70         return (((pixel >> 3) & 0x001f) |
  71                 ((pixel >> 5) & 0x07e0) |
  72                 ((pixel >> 8) & 0xf800));
  73 }
  74 
  75 static inline u16 get_pixel_val16(const uint8_t *pixel, int log_bpp)
  76 {
  77         u16 pixel_val16;
  78         if (log_bpp == 1)
  79                 pixel_val16 = *(const uint16_t *)pixel;
  80         else
  81                 pixel_val16 = pixel32_to_be16(*(const uint32_t *)pixel);
  82         return pixel_val16;
  83 }
  84 
  85 /*
  86  * Render a command stream for an encoded horizontal line segment of pixels.
  87  *
  88  * A command buffer holds several commands.
  89  * It always begins with a fresh command header
  90  * (the protocol doesn't require this, but we enforce it to allow
  91  * multiple buffers to be potentially encoded and sent in parallel).
  92  * A single command encodes one contiguous horizontal line of pixels
  93  *
  94  * The function relies on the client to do all allocation, so that
  95  * rendering can be done directly to output buffers (e.g. USB URBs).
  96  * The function fills the supplied command buffer, providing information
  97  * on where it left off, so the client may call in again with additional
  98  * buffers if the line will take several buffers to complete.
  99  *
 100  * A single command can transmit a maximum of 256 pixels,
 101  * regardless of the compression ratio (protocol design limit).
 102  * To the hardware, 0 for a size byte means 256
 103  *
 104  * Rather than 256 pixel commands which are either rl or raw encoded,
 105  * the rlx command simply assumes alternating raw and rl spans within one cmd.
 106  * This has a slightly larger header overhead, but produces more even results.
 107  * It also processes all data (read and write) in a single pass.
 108  * Performance benchmarks of common cases show it having just slightly better
 109  * compression than 256 pixel raw or rle commands, with similar CPU consumpion.
 110  * But for very rl friendly data, will compress not quite as well.
 111  */
 112 static void udl_compress_hline16(
 113         const u8 **pixel_start_ptr,
 114         const u8 *const pixel_end,
 115         uint32_t *device_address_ptr,
 116         uint8_t **command_buffer_ptr,
 117         const uint8_t *const cmd_buffer_end, int log_bpp)
 118 {
 119         const int bpp = 1 << log_bpp;
 120         const u8 *pixel = *pixel_start_ptr;
 121         uint32_t dev_addr  = *device_address_ptr;
 122         uint8_t *cmd = *command_buffer_ptr;
 123 
 124         while ((pixel_end > pixel) &&
 125                (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
 126                 uint8_t *raw_pixels_count_byte = NULL;
 127                 uint8_t *cmd_pixels_count_byte = NULL;
 128                 const u8 *raw_pixel_start = NULL;
 129                 const u8 *cmd_pixel_start, *cmd_pixel_end = NULL;
 130                 uint16_t pixel_val16;
 131 
 132                 *cmd++ = 0xaf;
 133                 *cmd++ = 0x6b;
 134                 *cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
 135                 *cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
 136                 *cmd++ = (uint8_t) ((dev_addr) & 0xFF);
 137 
 138                 cmd_pixels_count_byte = cmd++; /*  we'll know this later */
 139                 cmd_pixel_start = pixel;
 140 
 141                 raw_pixels_count_byte = cmd++; /*  we'll know this later */
 142                 raw_pixel_start = pixel;
 143 
 144                 cmd_pixel_end = pixel + (min3(MAX_CMD_PIXELS + 1UL,
 145                                         (unsigned long)(pixel_end - pixel) >> log_bpp,
 146                                         (unsigned long)(cmd_buffer_end - 1 - cmd) / 2) << log_bpp);
 147 
 148                 pixel_val16 = get_pixel_val16(pixel, log_bpp);
 149 
 150                 while (pixel < cmd_pixel_end) {
 151                         const u8 *const start = pixel;
 152                         const uint16_t repeating_pixel_val16 = pixel_val16;
 153 
 154                         put_unaligned_be16(pixel_val16, cmd);
 155 
 156                         cmd += 2;
 157                         pixel += bpp;
 158 
 159                         while (pixel < cmd_pixel_end) {
 160                                 pixel_val16 = get_pixel_val16(pixel, log_bpp);
 161                                 if (pixel_val16 != repeating_pixel_val16)
 162                                         break;
 163                                 pixel += bpp;
 164                         }
 165 
 166                         if (unlikely(pixel > start + bpp)) {
 167                                 /* go back and fill in raw pixel count */
 168                                 *raw_pixels_count_byte = (((start -
 169                                                 raw_pixel_start) >> log_bpp) + 1) & 0xFF;
 170 
 171                                 /* immediately after raw data is repeat byte */
 172                                 *cmd++ = (((pixel - start) >> log_bpp) - 1) & 0xFF;
 173 
 174                                 /* Then start another raw pixel span */
 175                                 raw_pixel_start = pixel;
 176                                 raw_pixels_count_byte = cmd++;
 177                         }
 178                 }
 179 
 180                 if (pixel > raw_pixel_start) {
 181                         /* finalize last RAW span */
 182                         *raw_pixels_count_byte = ((pixel - raw_pixel_start) >> log_bpp) & 0xFF;
 183                 } else {
 184                         /* undo unused byte */
 185                         cmd--;
 186                 }
 187 
 188                 *cmd_pixels_count_byte = ((pixel - cmd_pixel_start) >> log_bpp) & 0xFF;
 189                 dev_addr += ((pixel - cmd_pixel_start) >> log_bpp) * 2;
 190         }
 191 
 192         if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
 193                 /* Fill leftover bytes with no-ops */
 194                 if (cmd_buffer_end > cmd)
 195                         memset(cmd, 0xAF, cmd_buffer_end - cmd);
 196                 cmd = (uint8_t *) cmd_buffer_end;
 197         }
 198 
 199         *command_buffer_ptr = cmd;
 200         *pixel_start_ptr = pixel;
 201         *device_address_ptr = dev_addr;
 202 
 203         return;
 204 }
 205 
 206 /*
 207  * There are 3 copies of every pixel: The front buffer that the fbdev
 208  * client renders to, the actual framebuffer across the USB bus in hardware
 209  * (that we can only write to, slowly, and can never read), and (optionally)
 210  * our shadow copy that tracks what's been sent to that hardware buffer.
 211  */
 212 int udl_render_hline(struct drm_device *dev, int log_bpp, struct urb **urb_ptr,
 213                      const char *front, char **urb_buf_ptr,
 214                      u32 byte_offset, u32 device_byte_offset,
 215                      u32 byte_width,
 216                      int *ident_ptr, int *sent_ptr)
 217 {
 218         const u8 *line_start, *line_end, *next_pixel;
 219         u32 base16 = 0 + (device_byte_offset >> log_bpp) * 2;
 220         struct urb *urb = *urb_ptr;
 221         u8 *cmd = *urb_buf_ptr;
 222         u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
 223 
 224         BUG_ON(!(log_bpp == 1 || log_bpp == 2));
 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, log_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