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.
Changes compared to v1[1]: - Add Acked-by, - Use two separate helpers instead of a single combined helper, - Reorder operands in DIV_ROUND_UP() to improve readability.
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 applying!
[1] https://lore.kernel.org/dri-devel/20210714145804.2530727-1-geert@linux-m68k....
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_{col,page}_range() video: fbdev: ssd1307fb: Optimize screen updates video: fbdev: ssd1307fb: Cache address ranges
drivers/video/fbdev/ssd1307fb.c | 151 ++++++++++++++++++++++---------- 1 file changed, 104 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 Acked-by: Sam Ravnborg sam@ravnborg.org --- v2: - Add Acked-by. --- 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 Acked-by: Sam Ravnborg sam@ravnborg.org --- v2: - Add Acked-by. --- 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 two helper functions.
Signed-off-by: Geert Uytterhoeven geert@linux-m68k.org Acked-by: Sam Ravnborg sam@ravnborg.org --- v2: - Use two separate helpers instead of a single combined helper, - Add Acked-by. --- drivers/video/fbdev/ssd1307fb.c | 57 +++++++++++++++++++++------------ 1 file changed, 37 insertions(+), 20 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index 6d7bd025bca1a175..86eb9c99a783f0da 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -152,6 +152,40 @@ static inline int ssd1307fb_write_cmd(struct i2c_client *client, u8 cmd) return ret; }
+static int ssd1307fb_set_col_range(struct ssd1307fb_par *par, u8 col_start, + u8 cols) +{ + u8 col_end = col_start + cols - 1; + int ret; + + 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; + + return ssd1307fb_write_cmd(par->client, col_end); +} + +static int ssd1307fb_set_page_range(struct ssd1307fb_par *par, u8 page_start, + u8 pages) +{ + u8 page_end = page_start + pages - 1; + int ret; + + 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; @@ -462,30 +496,13 @@ static int ssd1307fb_init(struct ssd1307fb_par *par) 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); + ret = ssd1307fb_set_col_range(par, par->col_offset, par->width); 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); + ret = ssd1307fb_set_page_range(par, 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 calls to ssd1307fb_set_col_range() and ssd1307fb_set_page_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 --- v2: - Reorder operands in DIV_ROUND_UP() to improve readability, - Rebase. --- drivers/video/fbdev/ssd1307fb.c | 50 +++++++++++++++++++-------------- 1 file changed, 29 insertions(+), 21 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index 86eb9c99a783f0da..9aed5ee0094f2d95 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -186,16 +186,18 @@ static int ssd1307fb_set_page_range(struct ssd1307fb_par *par, u8 page_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(y % 8 + height, 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;
@@ -228,13 +230,21 @@ 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_col_range(par, par->col_offset + x, width); + if (ret < 0) + goto out_free; + + ret = ssd1307fb_set_page_range(par, 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++) { @@ -247,11 +257,17 @@ 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) @@ -301,21 +317,24 @@ 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 = { @@ -495,17 +514,6 @@ static int ssd1307fb_init(struct ssd1307fb_par *par) if (ret < 0) return ret;
- /* Set column range */ - ret = ssd1307fb_set_col_range(par, par->col_offset, par->width); - if (ret < 0) - return ret; - - /* Set page range */ - ret = ssd1307fb_set_page_range(par, 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 Acked-by: Sam Ravnborg sam@ravnborg.org --- v2: - Add Acked-by, - Rebase. --- drivers/video/fbdev/ssd1307fb.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-)
diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index 9aed5ee0094f2d95..1e2f71c2f8a8bc78 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 { @@ -158,6 +163,9 @@ static int ssd1307fb_set_col_range(struct ssd1307fb_par *par, u8 col_start, u8 col_end = col_start + cols - 1; int ret;
+ if (col_start == par->col_start && col_end == par->col_end) + return 0; + ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_COL_RANGE); if (ret < 0) return ret; @@ -166,7 +174,13 @@ static int ssd1307fb_set_col_range(struct ssd1307fb_par *par, u8 col_start, if (ret < 0) return ret;
- return ssd1307fb_write_cmd(par->client, col_end); + ret = ssd1307fb_write_cmd(par->client, col_end); + if (ret < 0) + return ret; + + par->col_start = col_start; + par->col_end = col_end; + return 0; }
static int ssd1307fb_set_page_range(struct ssd1307fb_par *par, u8 page_start, @@ -175,6 +189,9 @@ static int ssd1307fb_set_page_range(struct ssd1307fb_par *par, u8 page_start, u8 page_end = page_start + pages - 1; int ret;
+ if (page_start == par->page_start && page_end == par->page_end) + return 0; + ret = ssd1307fb_write_cmd(par->client, SSD1307FB_SET_PAGE_RANGE); if (ret < 0) return ret; @@ -183,7 +200,13 @@ static int ssd1307fb_set_page_range(struct ssd1307fb_par *par, u8 page_start, if (ret < 0) return ret;
- return ssd1307fb_write_cmd(par->client, page_end); + ret = ssd1307fb_write_cmd(par->client, page_end); + if (ret < 0) + return ret; + + par->page_start = page_start; + par->page_end = page_end; + return 0; }
static int ssd1307fb_update_rect(struct ssd1307fb_par *par, unsigned int x,
Hi Geert, On Tue, Jul 27, 2021 at 03:47:25PM +0200, Geert Uytterhoeven wrote:
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.
Changes compared to v1[1]:
- Add Acked-by,
- Use two separate helpers instead of a single combined helper,
- Reorder operands in DIV_ROUND_UP() to improve readability.
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 applying!
Thanks for the respin - patches are now applied to drm-misc-next.
Sam
dri-devel@lists.freedesktop.org
-
Geert Uytterhoeven -
Sam Ravnborg