bob prohaska  wrote:
> Just did an upgrade on my Pi3b+, and the "experimental GL driver"
> seems to be a bit faster than default. It also fixes the upside down
> maps problem in Chromium.
>
> Unfortunately, it locks up solid when the machine is left idle. The
> red light is on, but the green light doesn't blink. Ctrl-alt-f2 does
> nothing. The only recourse seems to be power cycling. If anybody knows
> a fix, please post it.

You could try switching the CPU governor policy from the default
"ondemand" to "performance", so that it doesn't drop the clock speed
when under low load:

echo -n performance | sudo tee
/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

Other settings are documented here:
https://www.kernel.org/doc/html/v4.19/admin-guide/pm/cpufreq.html

This isn't something I've tried myself, I don't even have a Pi3, but
it seems a logical place to start.

> More generally, what is the state of GPU support on the Pi? A couple
> years ago it sounded as if Eric Anholt would write an open source
> driver.
>
> AIUI, the GPU is a second processor with its own vector-oriented
> instruction set. Seems like one has the choice of writing assembler
> for the GPU, or writing a code generator for the back end of an
> existing compiler and then writing high-level (probably c) routines
> that compile into a kernel module.....I'm no programmer, so just
> guessing here.
>
> If anybody can shed light or pointers to further reading please do!

The GPU plays a big role in the boot process (at least on the BCM2835
Pis), so some docs describing the boot process in detail may go into
how GPU code works.

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