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 #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 } 218