![Chris Wilson](/assets/img/avatar_default.png)
As we use a variable length the compiler does not realise that it is a fixed value of either 2 or 4 bytes. Instead of performing the inline comparison itself, the compiler inserts a function call to the generic memcmp routine which is optimised for long comparisons of variable length. That turns out to be quite expensive... Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Dave Airlie <airlied@redhat.com>
265 lines
7.7 KiB
C
265 lines
7.7 KiB
C
/*
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* Copyright (C) 2012 Red Hat
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* based in parts on udlfb.c:
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* Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
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* Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
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* Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License v2. See the file COPYING in the main directory of this archive for
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* more details.
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/fb.h>
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#include <linux/prefetch.h>
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#include <drm/drmP.h>
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#include "udl_drv.h"
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#define MAX_CMD_PIXELS 255
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#define RLX_HEADER_BYTES 7
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#define MIN_RLX_PIX_BYTES 4
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#define MIN_RLX_CMD_BYTES (RLX_HEADER_BYTES + MIN_RLX_PIX_BYTES)
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#define RLE_HEADER_BYTES 6
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#define MIN_RLE_PIX_BYTES 3
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#define MIN_RLE_CMD_BYTES (RLE_HEADER_BYTES + MIN_RLE_PIX_BYTES)
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#define RAW_HEADER_BYTES 6
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#define MIN_RAW_PIX_BYTES 2
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#define MIN_RAW_CMD_BYTES (RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)
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/*
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* Trims identical data from front and back of line
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* Sets new front buffer address and width
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* And returns byte count of identical pixels
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* Assumes CPU natural alignment (unsigned long)
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* for back and front buffer ptrs and width
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*/
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#if 0
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static int udl_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)
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{
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int j, k;
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const unsigned long *back = (const unsigned long *) bback;
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const unsigned long *front = (const unsigned long *) *bfront;
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const int width = *width_bytes / sizeof(unsigned long);
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int identical = width;
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int start = width;
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int end = width;
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prefetch((void *) front);
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prefetch((void *) back);
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for (j = 0; j < width; j++) {
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if (back[j] != front[j]) {
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start = j;
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break;
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}
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}
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for (k = width - 1; k > j; k--) {
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if (back[k] != front[k]) {
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end = k+1;
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break;
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}
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}
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identical = start + (width - end);
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*bfront = (u8 *) &front[start];
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*width_bytes = (end - start) * sizeof(unsigned long);
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return identical * sizeof(unsigned long);
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}
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#endif
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static inline u16 pixel32_to_be16(const uint32_t pixel)
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{
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return (((pixel >> 3) & 0x001f) |
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((pixel >> 5) & 0x07e0) |
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((pixel >> 8) & 0xf800));
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}
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static bool pixel_repeats(const void *pixel, const uint32_t repeat, int bpp)
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{
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if (bpp == 2)
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return *(const uint16_t *)pixel == repeat;
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else
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return *(const uint32_t *)pixel == repeat;
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}
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/*
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* Render a command stream for an encoded horizontal line segment of pixels.
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*
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* A command buffer holds several commands.
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* It always begins with a fresh command header
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* (the protocol doesn't require this, but we enforce it to allow
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* multiple buffers to be potentially encoded and sent in parallel).
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* A single command encodes one contiguous horizontal line of pixels
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*
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* The function relies on the client to do all allocation, so that
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* rendering can be done directly to output buffers (e.g. USB URBs).
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* The function fills the supplied command buffer, providing information
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* on where it left off, so the client may call in again with additional
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* buffers if the line will take several buffers to complete.
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*
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* A single command can transmit a maximum of 256 pixels,
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* regardless of the compression ratio (protocol design limit).
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* To the hardware, 0 for a size byte means 256
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*
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* Rather than 256 pixel commands which are either rl or raw encoded,
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* the rlx command simply assumes alternating raw and rl spans within one cmd.
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* This has a slightly larger header overhead, but produces more even results.
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* It also processes all data (read and write) in a single pass.
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* Performance benchmarks of common cases show it having just slightly better
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* compression than 256 pixel raw or rle commands, with similar CPU consumpion.
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* But for very rl friendly data, will compress not quite as well.
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*/
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static void udl_compress_hline16(
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const u8 **pixel_start_ptr,
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const u8 *const pixel_end,
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uint32_t *device_address_ptr,
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uint8_t **command_buffer_ptr,
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const uint8_t *const cmd_buffer_end, int bpp)
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{
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const u8 *pixel = *pixel_start_ptr;
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uint32_t dev_addr = *device_address_ptr;
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uint8_t *cmd = *command_buffer_ptr;
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while ((pixel_end > pixel) &&
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(cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
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uint8_t *raw_pixels_count_byte = NULL;
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uint8_t *cmd_pixels_count_byte = NULL;
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const u8 *raw_pixel_start = NULL;
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const u8 *cmd_pixel_start, *cmd_pixel_end = NULL;
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prefetchw((void *) cmd); /* pull in one cache line at least */
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*cmd++ = 0xaf;
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*cmd++ = 0x6b;
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*cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
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*cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
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*cmd++ = (uint8_t) ((dev_addr) & 0xFF);
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cmd_pixels_count_byte = cmd++; /* we'll know this later */
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cmd_pixel_start = pixel;
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raw_pixels_count_byte = cmd++; /* we'll know this later */
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raw_pixel_start = pixel;
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cmd_pixel_end = pixel + (min(MAX_CMD_PIXELS + 1,
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min((int)(pixel_end - pixel) / bpp,
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(int)(cmd_buffer_end - cmd) / 2))) * bpp;
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prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
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while (pixel < cmd_pixel_end) {
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const u8 *const start = pixel;
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u32 repeating_pixel;
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if (bpp == 2) {
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repeating_pixel = *(uint16_t *)pixel;
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*(uint16_t *)cmd = cpu_to_be16(repeating_pixel);
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} else {
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repeating_pixel = *(uint32_t *)pixel;
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*(uint16_t *)cmd = cpu_to_be16(pixel32_to_be16(repeating_pixel));
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}
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cmd += 2;
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pixel += bpp;
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if (unlikely((pixel < cmd_pixel_end) &&
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(pixel_repeats(pixel, repeating_pixel, bpp)))) {
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/* go back and fill in raw pixel count */
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*raw_pixels_count_byte = (((start -
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raw_pixel_start) / bpp) + 1) & 0xFF;
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while ((pixel < cmd_pixel_end) &&
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(pixel_repeats(pixel, repeating_pixel, bpp))) {
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pixel += bpp;
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}
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/* immediately after raw data is repeat byte */
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*cmd++ = (((pixel - start) / bpp) - 1) & 0xFF;
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/* Then start another raw pixel span */
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raw_pixel_start = pixel;
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raw_pixels_count_byte = cmd++;
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}
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}
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if (pixel > raw_pixel_start) {
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/* finalize last RAW span */
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*raw_pixels_count_byte = ((pixel-raw_pixel_start) / bpp) & 0xFF;
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}
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*cmd_pixels_count_byte = ((pixel - cmd_pixel_start) / bpp) & 0xFF;
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dev_addr += ((pixel - cmd_pixel_start) / bpp) * 2;
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}
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if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
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/* Fill leftover bytes with no-ops */
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if (cmd_buffer_end > cmd)
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memset(cmd, 0xAF, cmd_buffer_end - cmd);
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cmd = (uint8_t *) cmd_buffer_end;
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}
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*command_buffer_ptr = cmd;
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*pixel_start_ptr = pixel;
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*device_address_ptr = dev_addr;
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return;
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}
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/*
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* There are 3 copies of every pixel: The front buffer that the fbdev
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* client renders to, the actual framebuffer across the USB bus in hardware
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* (that we can only write to, slowly, and can never read), and (optionally)
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* our shadow copy that tracks what's been sent to that hardware buffer.
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*/
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int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
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const char *front, char **urb_buf_ptr,
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u32 byte_offset, u32 device_byte_offset,
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u32 byte_width,
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int *ident_ptr, int *sent_ptr)
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{
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const u8 *line_start, *line_end, *next_pixel;
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u32 base16 = 0 + (device_byte_offset / bpp) * 2;
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struct urb *urb = *urb_ptr;
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u8 *cmd = *urb_buf_ptr;
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u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
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BUG_ON(!(bpp == 2 || bpp == 4));
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line_start = (u8 *) (front + byte_offset);
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next_pixel = line_start;
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line_end = next_pixel + byte_width;
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while (next_pixel < line_end) {
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udl_compress_hline16(&next_pixel,
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line_end, &base16,
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(u8 **) &cmd, (u8 *) cmd_end, bpp);
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if (cmd >= cmd_end) {
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int len = cmd - (u8 *) urb->transfer_buffer;
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if (udl_submit_urb(dev, urb, len))
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return 1; /* lost pixels is set */
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*sent_ptr += len;
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urb = udl_get_urb(dev);
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if (!urb)
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return 1; /* lost_pixels is set */
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*urb_ptr = urb;
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cmd = urb->transfer_buffer;
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cmd_end = &cmd[urb->transfer_buffer_length];
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}
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}
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*urb_buf_ptr = cmd;
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return 0;
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}
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