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 <linux/unaligned.h>
  11
  12 #include "udl_drv.h"
  13 #include "udl_proto.h"
  14
  15 #define MAX_CMD_PIXELS          255
  16
  17 #define RLX_HEADER_BYTES        7
  18 #define MIN_RLX_PIX_BYTES       4
  19 #define MIN_RLX_CMD_BYTES       (RLX_HEADER_BYTES + MIN_RLX_PIX_BYTES)
  20
  21 #define RLE_HEADER_BYTES        6
  22 #define MIN_RLE_PIX_BYTES       3
  23 #define MIN_RLE_CMD_BYTES       (RLE_HEADER_BYTES + MIN_RLE_PIX_BYTES)
  24
  25 #define RAW_HEADER_BYTES        6
  26 #define MIN_RAW_PIX_BYTES       2
  27 #define MIN_RAW_CMD_BYTES       (RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)
  28
  29 static inline u16 pixel32_to_be16(const uint32_t pixel)
  30 {
  31         return (((pixel >> 3) & 0x001f) |
  32                 ((pixel >> 5) & 0x07e0) |
  33                 ((pixel >> 8) & 0xf800));
  34 }
  35
  36 static inline u16 get_pixel_val16(const uint8_t *pixel, int log_bpp)
  37 {
  38         u16 pixel_val16;
  39         if (log_bpp == 1)
  40                 pixel_val16 = *(const uint16_t *)pixel;
  41         else
  42                 pixel_val16 = pixel32_to_be16(*(const uint32_t *)pixel);
  43         return pixel_val16;
  44 }
  45
  46 /*
  47  * Render a command stream for an encoded horizontal line segment of pixels.
  48  *
  49  * A command buffer holds several commands.
  50  * It always begins with a fresh command header
  51  * (the protocol doesn't require this, but we enforce it to allow
  52  * multiple buffers to be potentially encoded and sent in parallel).
  53  * A single command encodes one contiguous horizontal line of pixels
  54  *
  55  * The function relies on the client to do all allocation, so that
  56  * rendering can be done directly to output buffers (e.g. USB URBs).
  57  * The function fills the supplied command buffer, providing information
  58  * on where it left off, so the client may call in again with additional
  59  * buffers if the line will take several buffers to complete.
  60  *
  61  * A single command can transmit a maximum of 256 pixels,
  62  * regardless of the compression ratio (protocol design limit).
  63  * To the hardware, 0 for a size byte means 256
  64  *
  65  * Rather than 256 pixel commands which are either rl or raw encoded,
  66  * the rlx command simply assumes alternating raw and rl spans within one cmd.
  67  * This has a slightly larger header overhead, but produces more even results.
  68  * It also processes all data (read and write) in a single pass.
  69  * Performance benchmarks of common cases show it having just slightly better
  70  * compression than 256 pixel raw or rle commands, with similar CPU consumpion.
  71  * But for very rl friendly data, will compress not quite as well.
  72  */
  73 static void udl_compress_hline16(
  74         const u8 **pixel_start_ptr,
  75         const u8 *const pixel_end,
  76         uint32_t *device_address_ptr,
  77         uint8_t **command_buffer_ptr,
  78         const uint8_t *const cmd_buffer_end, int log_bpp)
  79 {
  80         const int bpp = 1 << log_bpp;
  81         const u8 *pixel = *pixel_start_ptr;
  82         uint32_t dev_addr  = *device_address_ptr;
  83         uint8_t *cmd = *command_buffer_ptr;
  84
  85         while ((pixel_end > pixel) &&
  86                (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
  87                 uint8_t *raw_pixels_count_byte = NULL;
  88                 uint8_t *cmd_pixels_count_byte = NULL;
  89                 const u8 *raw_pixel_start = NULL;
  90                 const u8 *cmd_pixel_start, *cmd_pixel_end = NULL;
  91                 uint16_t pixel_val16;
  92
  93                 *cmd++ = UDL_MSG_BULK;
  94                 *cmd++ = UDL_CMD_WRITERLX16;
  95                 *cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
  96                 *cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
  97                 *cmd++ = (uint8_t) ((dev_addr) & 0xFF);
  98
  99                 cmd_pixels_count_byte = cmd++; /*  we'll know this later */
 100                 cmd_pixel_start = pixel;
 101
 102                 raw_pixels_count_byte = cmd++; /*  we'll know this later */
 103                 raw_pixel_start = pixel;
 104
 105                 cmd_pixel_end = pixel + (min3(MAX_CMD_PIXELS + 1UL,
 106                                         (unsigned long)(pixel_end - pixel) >> log_bpp,
 107                                         (unsigned long)(cmd_buffer_end - 1 - cmd) / 2) << log_bpp);
 108
 109                 pixel_val16 = get_pixel_val16(pixel, log_bpp);
 110
 111                 while (pixel < cmd_pixel_end) {
 112                         const u8 *const start = pixel;
 113                         const uint16_t repeating_pixel_val16 = pixel_val16;
 114
 115                         put_unaligned_be16(pixel_val16, cmd);
 116
 117                         cmd += 2;
 118                         pixel += bpp;
 119
 120                         while (pixel < cmd_pixel_end) {
 121                                 pixel_val16 = get_pixel_val16(pixel, log_bpp);
 122                                 if (pixel_val16 != repeating_pixel_val16)
 123                                         break;
 124                                 pixel += bpp;
 125                         }
 126
 127                         if (unlikely(pixel > start + bpp)) {
 128                                 /* go back and fill in raw pixel count */
 129                                 *raw_pixels_count_byte = (((start -
 130                                                 raw_pixel_start) >> log_bpp) + 1) & 0xFF;
 131
 132                                 /* immediately after raw data is repeat byte */
 133                                 *cmd++ = (((pixel - start) >> log_bpp) - 1) & 0xFF;
 134
 135                                 /* Then start another raw pixel span */
 136                                 raw_pixel_start = pixel;
 137                                 raw_pixels_count_byte = cmd++;
 138                         }
 139                 }
 140
 141                 if (pixel > raw_pixel_start) {
 142                         /* finalize last RAW span */
 143                         *raw_pixels_count_byte = ((pixel - raw_pixel_start) >> log_bpp) & 0xFF;
 144                 } else {
 145                         /* undo unused byte */
 146                         cmd--;
 147                 }
 148
 149                 *cmd_pixels_count_byte = ((pixel - cmd_pixel_start) >> log_bpp) & 0xFF;
 150                 dev_addr += ((pixel - cmd_pixel_start) >> log_bpp) * 2;
 151         }
 152
 153         if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
 154                 /* Fill leftover bytes with no-ops */
 155                 if (cmd_buffer_end > cmd)
 156                         memset(cmd, UDL_MSG_BULK, cmd_buffer_end - cmd);
 157                 cmd = (uint8_t *) cmd_buffer_end;
 158         }
 159
 160         *command_buffer_ptr = cmd;
 161         *pixel_start_ptr = pixel;
 162         *device_address_ptr = dev_addr;
 163
 164         return;
 165 }
 166
 167 /*
 168  * There are 3 copies of every pixel: The front buffer that the fbdev
 169  * client renders to, the actual framebuffer across the USB bus in hardware
 170  * (that we can only write to, slowly, and can never read), and (optionally)
 171  * our shadow copy that tracks what's been sent to that hardware buffer.
 172  */
 173 int udl_render_hline(struct drm_device *dev, int log_bpp, struct urb **urb_ptr,
 174                      const char *front, char **urb_buf_ptr,
 175                      u32 byte_offset, u32 device_byte_offset,
 176                      u32 byte_width)
 177 {
 178         const u8 *line_start, *line_end, *next_pixel;
 179         u32 base16 = 0 + (device_byte_offset >> log_bpp) * 2;
 180         struct urb *urb = *urb_ptr;
 181         u8 *cmd = *urb_buf_ptr;
 182         u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
 183
 184         if (WARN_ON(!(log_bpp == 1 || log_bpp == 2))) {
 185                 /* need to finish URB at error from this function */
 186                 udl_urb_completion(urb);
 187                 return -EINVAL;
 188         }
 189
 190         line_start = (u8 *) (front + byte_offset);
 191         next_pixel = line_start;
 192         line_end = next_pixel + byte_width;
 193
 194         while (next_pixel < line_end) {
 195
 196                 udl_compress_hline16(&next_pixel,
 197                              line_end, &base16,
 198                              (u8 **) &cmd, (u8 *) cmd_end, log_bpp);
 199
 200                 if (cmd >= cmd_end) {
 201                         int len = cmd - (u8 *) urb->transfer_buffer;
 202                         int ret = udl_submit_urb(dev, urb, len);
 203                         if (ret)
 204                                 return ret;
 205                         urb = udl_get_urb(dev);
 206                         if (!urb)
 207                                 return -EAGAIN;
 208                         *urb_ptr = urb;
 209                         cmd = urb->transfer_buffer;
 210                         cmd_end = &cmd[urb->transfer_buffer_length];
 211                 }
 212         }
 213
 214         *urb_buf_ptr = cmd;
 215
 216         return 0;
 217 }