drivers/gpu/drm/udl/udl_transfer.c

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