Toshiba C50D-B-120 Part 5 - Firmware update

It's been a few months since I bought my new Toshiba laptop, and by and large, it's been working well. One issue I have had is an occasional artefact in text rendering- I assume a problem with the graphics driver.

I noticed that Debian Backports had some updated firmware for video drivers, so I wondered if this might help with my problem, but I just couldn't see the firmware update even though I have backports in my sources list.

To cut a long story short, the instructions page in the link above has the following line to add to sources list:

deb http://http.debian.net/debian jessie-backports main

To get firmware updates, it should of course be:

deb http://http.debian.net/debian jessie-backports main contrib non-free

(Firmware is non-free software.)

I've upgraded firmware as follows:

Removed the following packages: firmware-linux 
Upgraded the following packages: firmware-linux-nonfree (0.43) to 20151207-1~bpo8+1 
Installed the following packages: firmware-amd-graphics (20151207-1~bpo8+1) firmware-misc-nonfree (20151207-1~bpo8+1) 
Upgraded the following packages: firmware-atheros (0.43) to 20151207-1~bpo8+1

The rendering issue doesn't seem to have entirely disappeared, although first impressions are that it is happening less frequently.