Hi all,
This patch series optimizes console operations on ssd1307fb, after the customary fixes and cleanups.
Currently, each screen update triggers an I2C transfer of all screen data, up to 1 KiB of data for a 128x64 display, which takes at least 20 ms in Fast mode. While many displays are smaller, and thus require less data to be transferred, 20 ms is still an optimistic value, as the actual data transfer may be much slower, especially on bitbanged I2C drivers. After this series, the amount of data transfer is reduced, as fillrect, copyarea, and imageblit only update the rectangle that changed.
This has been tested on an Adafruit FeatherWing OLED with an SSD1306 controller and a 128x32 OLED, connected to an OrangeCrab ECP5 FPGA board running a 64 MHz VexRiscv RISC-V softcore, where it reduced the CPU usage for blinking the cursor from more than 70% to ca. 10%.
Thanks for your comments!
Geert Uytterhoeven (5): video: fbdev: ssd1307fb: Propagate errors via ssd1307fb_update_display() video: fbdev: ssd1307fb: Simplify ssd1307fb_update_display() video: fbdev: ssd1307fb: Extract ssd1307fb_set_address_range() video: fbdev: ssd1307fb: Optimize screen updates video: fbdev: ssd1307fb: Cache address ranges
drivers/video/fbdev/ssd1307fb.c | 143 +++++++++++++++++++++----------- 1 file changed, 96 insertions(+), 47 deletions(-)
Make ssd1307fb_update_display() return an error code, so callers that can handle failures can propagate it.
Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org --- drivers/video/fbdev/ssd1307fb.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index eda448b7a0c9d8ce..e6b6263e3bef847f 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -152,17 +152,17 @@ static inline int ssd1307fb_write_cmd(struct i2c_client *client, u8 cmd) return ret; }
-static void ssd1307fb_update_display(struct ssd1307fb_par *par) +static int ssd1307fb_update_display(struct ssd1307fb_par *par) { struct ssd1307fb_array *array; u8 *vmem = par->info->screen_buffer; unsigned int line_length = par->info->fix.line_length; unsigned int pages = DIV_ROUND_UP(par->height, 8); - int i, j, k; + int ret, i, j, k;
array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA); if (!array) - return; + return -ENOMEM;
/* * The screen is divided in pages, each having a height of 8 @@ -210,8 +210,9 @@ static void ssd1307fb_update_display(struct ssd1307fb_par *par) } }
- ssd1307fb_write_array(par->client, array, par->width * pages); + ret = ssd1307fb_write_array(par->client, array, par->width * pages); kfree(array); + return ret; }
@@ -222,6 +223,7 @@ static ssize_t ssd1307fb_write(struct fb_info *info, const char __user *buf, unsigned long total_size; unsigned long p = *ppos; void *dst; + int ret;
total_size = info->fix.smem_len;
@@ -239,7 +241,9 @@ static ssize_t ssd1307fb_write(struct fb_info *info, const char __user *buf, if (copy_from_user(dst, buf, count)) return -EFAULT;
- ssd1307fb_update_display(par); + ret = ssd1307fb_update_display(par); + if (ret < 0) + return ret;
*ppos += count;
@@ -483,7 +487,9 @@ static int ssd1307fb_init(struct ssd1307fb_par *par) return ret;
/* Clear the screen */ - ssd1307fb_update_display(par); + ret = ssd1307fb_update_display(par); + if (ret < 0) + return ret;
/* Turn on the display */ ret = ssd1307fb_write_cmd(par->client, SSD1307FB_DISPLAY_ON);
Simplify the nested loops to handle conversion from linear frame buffer to ssd1307 page layout: 1. Move last page handling one level up, as the value of "m" is the same inside a page, 2. array->data[] is filled linearly, so there is no need to recalculate array_idx over and over again; a simple increment is sufficient.
Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org --- drivers/video/fbdev/ssd1307fb.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index e6b6263e3bef847f..6d7bd025bca1a175 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -158,6 +158,7 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) u8 *vmem = par->info->screen_buffer; unsigned int line_length = par->info->fix.line_length; unsigned int pages = DIV_ROUND_UP(par->height, 8); + u32 array_idx = 0; int ret, i, j, k;
array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA); @@ -194,19 +195,21 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) */
for (i = 0; i < pages; i++) { + int m = 8; + + /* Last page may be partial */ + if (i + 1 == pages && par->height % 8) + m = par->height % 8; for (j = 0; j < par->width; j++) { - int m = 8; - u32 array_idx = i * par->width + j; - array->data[array_idx] = 0; - /* Last page may be partial */ - if (i + 1 == pages && par->height % 8) - m = par->height % 8; + u8 data = 0; + for (k = 0; k < m; k++) { u8 byte = vmem[(8 * i + k) * line_length + j / 8]; u8 bit = (byte >> (j % 8)) & 1; - array->data[array_idx] |= bit << k; + data |= bit << k; } + array->data[array_idx++] = data; } }
Extract the code to set the column and page ranges into a helper function.
Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org --- drivers/video/fbdev/ssd1307fb.c | 61 +++++++++++++++++++-------------- 1 file changed, 36 insertions(+), 25 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index 6d7bd025bca1a175..cfa27ea0feab4f01 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -152,6 +152,38 @@ static inline int ssd1307fb_write_cmd(struct i2c_client *client, u8 cmd) return ret; }
+static int ssd1307fb_set_address_range(struct ssd1307fb_par *par, u8 col_start, + u8 cols, u8 page_start, u8 pages) +{ + u8 col_end = col_start + cols - 1; + u8 page_end = page_start + pages - 1; + int ret; + + /* Set column range */ + ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COL_RANGE); + if (ret < 0) + return ret; + + ret = ssd1307fb_write_cmd(par->client, col_start); + if (ret < 0) + return ret; + + ret = ssd1307fb_write_cmd(par->client, col_end); + if (ret < 0) + return ret; + + /* Set page range */ + ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_PAGE_RANGE); + if (ret < 0) + return ret; + + ret = ssd1307fb_write_cmd(par->client, page_start); + if (ret < 0) + return ret; + + return ssd1307fb_write_cmd(par->client, page_end); +} + static int ssd1307fb_update_display(struct ssd1307fb_par *par) { struct ssd1307fb_array *array; @@ -461,31 +493,10 @@ static int ssd1307fb_init(struct ssd1307fb_par *par) if (ret < 0) return ret;
- /* Set column range */ - ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COL_RANGE); - if (ret < 0) - return ret; - - ret = ssd1307fb_write_cmd(par->client, par->col_offset); - if (ret < 0) - return ret; - - ret = ssd1307fb_write_cmd(par->client, par->col_offset + par->width - 1); - if (ret < 0) - return ret; - - /* Set page range */ - ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_PAGE_RANGE); - if (ret < 0) - return ret; - - ret = ssd1307fb_write_cmd(par->client, par->page_offset); - if (ret < 0) - return ret; - - ret = ssd1307fb_write_cmd(par->client, - par->page_offset + - DIV_ROUND_UP(par->height, 8) - 1); + /* Set column and page range */ + ret = ssd1307fb_set_address_range(par, par->col_offset, par->width, + par->page_offset, + DIV_ROUND_UP(par->height, 8)); if (ret < 0) return ret;
Currently, each screen update triggers an I2C transfer of all screen data, up to 1 KiB of data for a 128x64 display, which takes at least 20 ms in Fast mode.
Reduce the amount of transferred data by only updating the rectangle that changed. Remove the call to ssd1307fb_set_address_range() during initialization, as ssd1307fb_update_rect() now takes care of that.
Note that for now the optimized operation is only used for fillrect, copyarea, and imageblit, which are used by fbcon.
Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org --- drivers/video/fbdev/ssd1307fb.c | 43 ++++++++++++++++++++------------- 1 file changed, 26 insertions(+), 17 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index cfa27ea0feab4f01..8e3d4be74723b9bf 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -184,16 +184,18 @@ static int ssd1307fb_set_address_range(struct ssd1307fb_par *par, u8 col_start, return ssd1307fb_write_cmd(par->client, page_end); }
-static int ssd1307fb_update_display(struct ssd1307fb_par *par) +static int ssd1307fb_update_rect(struct ssd1307fb_par *par, unsigned int x, + unsigned int y, unsigned int width, + unsigned int height) { struct ssd1307fb_array *array; u8 *vmem = par->info->screen_buffer; unsigned int line_length = par->info->fix.line_length; - unsigned int pages = DIV_ROUND_UP(par->height, 8); + unsigned int pages = DIV_ROUND_UP(height + y % 8, 8); u32 array_idx = 0; int ret, i, j, k;
- array = ssd1307fb_alloc_array(par->width * pages, SSD1307FB_DATA); + array = ssd1307fb_alloc_array(width * pages, SSD1307FB_DATA); if (!array) return -ENOMEM;
@@ -226,13 +228,18 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) * (5) A4 B4 C4 D4 E4 F4 G4 H4 */
- for (i = 0; i < pages; i++) { + ret = ssd1307fb_set_address_range(par, par->col_offset + x, width, + par->page_offset + y / 8, pages); + if (ret < 0) + goto out_free; + + for (i = y / 8; i < y / 8 + pages; i++) { int m = 8;
/* Last page may be partial */ - if (i + 1 == pages && par->height % 8) + if (8 * (i + 1) > par->height) m = par->height % 8; - for (j = 0; j < par->width; j++) { + for (j = x; j < x + width; j++) { u8 data = 0;
for (k = 0; k < m; k++) { @@ -245,11 +252,17 @@ static int ssd1307fb_update_display(struct ssd1307fb_par *par) } }
- ret = ssd1307fb_write_array(par->client, array, par->width * pages); + ret = ssd1307fb_write_array(par->client, array, width * pages); + +out_free: kfree(array); return ret; }
+static int ssd1307fb_update_display(struct ssd1307fb_par *par) +{ + return ssd1307fb_update_rect(par, 0, 0, par->width, par->height); +}
static ssize_t ssd1307fb_write(struct fb_info *info, const char __user *buf, size_t count, loff_t *ppos) @@ -299,21 +312,24 @@ static void ssd1307fb_fillrect(struct fb_info *info, const struct fb_fillrect *r { struct ssd1307fb_par *par = info->par; sys_fillrect(info, rect); - ssd1307fb_update_display(par); + ssd1307fb_update_rect(par, rect->dx, rect->dy, rect->width, + rect->height); }
static void ssd1307fb_copyarea(struct fb_info *info, const struct fb_copyarea *area) { struct ssd1307fb_par *par = info->par; sys_copyarea(info, area); - ssd1307fb_update_display(par); + ssd1307fb_update_rect(par, area->dx, area->dy, area->width, + area->height); }
static void ssd1307fb_imageblit(struct fb_info *info, const struct fb_image *image) { struct ssd1307fb_par *par = info->par; sys_imageblit(info, image); - ssd1307fb_update_display(par); + ssd1307fb_update_rect(par, image->dx, image->dy, image->width, + image->height); }
static const struct fb_ops ssd1307fb_ops = { @@ -493,13 +509,6 @@ static int ssd1307fb_init(struct ssd1307fb_par *par) if (ret < 0) return ret;
- /* Set column and page range */ - ret = ssd1307fb_set_address_range(par, par->col_offset, par->width, - par->page_offset, - DIV_ROUND_UP(par->height, 8)); - if (ret < 0) - return ret; - /* Clear the screen */ ret = ssd1307fb_update_display(par); if (ret < 0)
Cache the column and page ranges, to avoid doing unneeded I2C transfers when the values haven't changed.
Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org --- drivers/video/fbdev/ssd1307fb.c | 52 +++++++++++++++++++++++---------- 1 file changed, 36 insertions(+), 16 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index 8e3d4be74723b9bf..23b43ce479898813 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -82,6 +82,11 @@ struct ssd1307fb_par { struct regulator *vbat_reg; u32 vcomh; u32 width; + /* Cached address ranges */ + u8 col_start; + u8 col_end; + u8 page_start; + u8 page_end; };
struct ssd1307fb_array { @@ -160,28 +165,43 @@ static int ssd1307fb_set_address_range(struct ssd1307fb_par *par, u8 col_start, int ret;
/* Set column range */ - ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COL_RANGE); - if (ret < 0) - return ret; + if (col_start != par->col_start || col_end != par->col_end) { + ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COL_RANGE); + if (ret < 0) + return ret;
- ret = ssd1307fb_write_cmd(par->client, col_start); - if (ret < 0) - return ret; + ret = ssd1307fb_write_cmd(par->client, col_start); + if (ret < 0) + return ret;
- ret = ssd1307fb_write_cmd(par->client, col_end); - if (ret < 0) - return ret; + ret = ssd1307fb_write_cmd(par->client, col_end); + if (ret < 0) + return ret; + + par->col_start = col_start; + par->col_end = col_end; + }
/* Set page range */ - ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_PAGE_RANGE); - if (ret < 0) - return ret; + if (page_start != par->page_start || page_end != par->page_end) { + ret = ssd1307fb_write_cmd(par->client, + SSD1307FB_SET_PAGE_RANGE); + if (ret < 0) + return ret;
- ret = ssd1307fb_write_cmd(par->client, page_start); - if (ret < 0) - return ret; + ret = ssd1307fb_write_cmd(par->client, page_start); + if (ret < 0) + return ret; + + ret = ssd1307fb_write_cmd(par->client, page_end); + if (ret < 0) + return ret;
- return ssd1307fb_write_cmd(par->client, page_end); + par->page_start = page_start; + par->page_end = page_end; + } + + return 0; }
static int ssd1307fb_update_rect(struct ssd1307fb_par *par, unsigned int x,
dri-devel@lists.freedesktop.org
-
Geert Uytterhoeven