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udl-kms: avoid division
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commit 91ba11f upstream.

Division is slow, so it shouldn't be done by the pixel generating code.
The driver supports only 2 or 4 bytes per pixel, so we can replace
division with a shift.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Mikulas Patocka authored and Greg Kroah-Hartman committed Sep 5, 2018
1 parent c0357c1 commit f337a54
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Showing 3 changed files with 30 additions and 26 deletions.
2 changes: 1 addition & 1 deletion drivers/gpu/drm/udl/udl_drv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -110,7 +110,7 @@ udl_fb_user_fb_create(struct drm_device *dev,
struct drm_file *file,
const struct drm_mode_fb_cmd2 *mode_cmd);

int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
int udl_render_hline(struct drm_device *dev, int log_bpp, struct urb **urb_ptr,
const char *front, char **urb_buf_ptr,
u32 byte_offset, u32 device_byte_offset, u32 byte_width,
int *ident_ptr, int *sent_ptr);
Expand Down
15 changes: 9 additions & 6 deletions drivers/gpu/drm/udl/udl_fb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,10 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
int bytes_identical = 0;
struct urb *urb;
int aligned_x;
int bpp = fb->base.format->cpp[0];
int log_bpp;

BUG_ON(!is_power_of_2(fb->base.format->cpp[0]));
log_bpp = __ffs(fb->base.format->cpp[0]);

if (!fb->active_16)
return 0;
Expand Down Expand Up @@ -125,12 +128,12 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,

for (i = y; i < y + height ; i++) {
const int line_offset = fb->base.pitches[0] * i;
const int byte_offset = line_offset + (x * bpp);
const int dev_byte_offset = (fb->base.width * bpp * i) + (x * bpp);
if (udl_render_hline(dev, bpp, &urb,
const int byte_offset = line_offset + (x << log_bpp);
const int dev_byte_offset = (fb->base.width * i + x) << log_bpp;
if (udl_render_hline(dev, log_bpp, &urb,
(char *) fb->obj->vmapping,
&cmd, byte_offset, dev_byte_offset,
width * bpp,
width << log_bpp,
&bytes_identical, &bytes_sent))
goto error;
}
Expand All @@ -149,7 +152,7 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
error:
atomic_add(bytes_sent, &udl->bytes_sent);
atomic_add(bytes_identical, &udl->bytes_identical);
atomic_add(width*height*bpp, &udl->bytes_rendered);
atomic_add((width * height) << log_bpp, &udl->bytes_rendered);
end_cycles = get_cycles();
atomic_add(((unsigned int) ((end_cycles - start_cycles)
>> 10)), /* Kcycles */
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39 changes: 20 additions & 19 deletions drivers/gpu/drm/udl/udl_transfer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -83,12 +83,12 @@ static inline u16 pixel32_to_be16(const uint32_t pixel)
((pixel >> 8) & 0xf800));
}

static inline u16 get_pixel_val16(const uint8_t *pixel, int bpp)
static inline u16 get_pixel_val16(const uint8_t *pixel, int log_bpp)
{
u16 pixel_val16 = 0;
if (bpp == 2)
u16 pixel_val16;
if (log_bpp == 1)
pixel_val16 = *(const uint16_t *)pixel;
else if (bpp == 4)
else
pixel_val16 = pixel32_to_be16(*(const uint32_t *)pixel);
return pixel_val16;
}
Expand Down Expand Up @@ -125,8 +125,9 @@ static void udl_compress_hline16(
const u8 *const pixel_end,
uint32_t *device_address_ptr,
uint8_t **command_buffer_ptr,
const uint8_t *const cmd_buffer_end, int bpp)
const uint8_t *const cmd_buffer_end, int log_bpp)
{
const int bpp = 1 << log_bpp;
const u8 *pixel = *pixel_start_ptr;
uint32_t dev_addr = *device_address_ptr;
uint8_t *cmd = *command_buffer_ptr;
Expand All @@ -153,12 +154,12 @@ static void udl_compress_hline16(
raw_pixels_count_byte = cmd++; /* we'll know this later */
raw_pixel_start = pixel;

cmd_pixel_end = pixel + min3(MAX_CMD_PIXELS + 1UL,
(unsigned long)(pixel_end - pixel) / bpp,
(unsigned long)(cmd_buffer_end - 1 - cmd) / 2) * bpp;
cmd_pixel_end = pixel + (min3(MAX_CMD_PIXELS + 1UL,
(unsigned long)(pixel_end - pixel) >> log_bpp,
(unsigned long)(cmd_buffer_end - 1 - cmd) / 2) << log_bpp);

prefetch_range((void *) pixel, cmd_pixel_end - pixel);
pixel_val16 = get_pixel_val16(pixel, bpp);
pixel_val16 = get_pixel_val16(pixel, log_bpp);

while (pixel < cmd_pixel_end) {
const u8 *const start = pixel;
Expand All @@ -170,7 +171,7 @@ static void udl_compress_hline16(
pixel += bpp;

while (pixel < cmd_pixel_end) {
pixel_val16 = get_pixel_val16(pixel, bpp);
pixel_val16 = get_pixel_val16(pixel, log_bpp);
if (pixel_val16 != repeating_pixel_val16)
break;
pixel += bpp;
Expand All @@ -179,10 +180,10 @@ static void udl_compress_hline16(
if (unlikely(pixel > start + bpp)) {
/* go back and fill in raw pixel count */
*raw_pixels_count_byte = (((start -
raw_pixel_start) / bpp) + 1) & 0xFF;
raw_pixel_start) >> log_bpp) + 1) & 0xFF;

/* immediately after raw data is repeat byte */
*cmd++ = (((pixel - start) / bpp) - 1) & 0xFF;
*cmd++ = (((pixel - start) >> log_bpp) - 1) & 0xFF;

/* Then start another raw pixel span */
raw_pixel_start = pixel;
Expand All @@ -192,14 +193,14 @@ static void udl_compress_hline16(

if (pixel > raw_pixel_start) {
/* finalize last RAW span */
*raw_pixels_count_byte = ((pixel-raw_pixel_start) / bpp) & 0xFF;
*raw_pixels_count_byte = ((pixel - raw_pixel_start) >> log_bpp) & 0xFF;
} else {
/* undo unused byte */
cmd--;
}

*cmd_pixels_count_byte = ((pixel - cmd_pixel_start) / bpp) & 0xFF;
dev_addr += ((pixel - cmd_pixel_start) / bpp) * 2;
*cmd_pixels_count_byte = ((pixel - cmd_pixel_start) >> log_bpp) & 0xFF;
dev_addr += ((pixel - cmd_pixel_start) >> log_bpp) * 2;
}

if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
Expand All @@ -222,19 +223,19 @@ static void udl_compress_hline16(
* (that we can only write to, slowly, and can never read), and (optionally)
* our shadow copy that tracks what's been sent to that hardware buffer.
*/
int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,
int udl_render_hline(struct drm_device *dev, int log_bpp, struct urb **urb_ptr,
const char *front, char **urb_buf_ptr,
u32 byte_offset, u32 device_byte_offset,
u32 byte_width,
int *ident_ptr, int *sent_ptr)
{
const u8 *line_start, *line_end, *next_pixel;
u32 base16 = 0 + (device_byte_offset / bpp) * 2;
u32 base16 = 0 + (device_byte_offset >> log_bpp) * 2;
struct urb *urb = *urb_ptr;
u8 *cmd = *urb_buf_ptr;
u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;

BUG_ON(!(bpp == 2 || bpp == 4));
BUG_ON(!(log_bpp == 1 || log_bpp == 2));

line_start = (u8 *) (front + byte_offset);
next_pixel = line_start;
Expand All @@ -244,7 +245,7 @@ int udl_render_hline(struct drm_device *dev, int bpp, struct urb **urb_ptr,

udl_compress_hline16(&next_pixel,
line_end, &base16,
(u8 **) &cmd, (u8 *) cmd_end, bpp);
(u8 **) &cmd, (u8 *) cmd_end, log_bpp);

if (cmd >= cmd_end) {
int len = cmd - (u8 *) urb->transfer_buffer;
Expand Down

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