[PATCH 0/5] video: fbdev: ssd1307fb: Optimizations and improvements

From: Geert Uytterhoeven
Date: Tue May 18 2021 - 05:06:15 EST

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

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
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(-)




Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds