* Add preliminary support for TTY Serial/UART (#15)
* Use shadow_buffer instead of VGA buffer to get a framebuffer-agnostic TTY supprot
* Added menu browsing & inputs from Serial TTY (#15)
* Add fix for degree symbol on TTY. Correct serial.c & serial.h file created with CRLF (#15)
* Move tty_error_redraw() to insure correct redraw when a error occurs
* Many reindent / cleanup
* Various optimization from @martinwhitaker comments
We need to pass the physical address of the MADT to parse_madt(), not the
virtual address of the table signature, because parse_madt() needs to call
map_region() again to ensure the full table is mapped into virtual memory.
There is an unavoidable race between one core halting after decrementing
the barrier count and another core sending it the wakeup NMI. This can
only occur if the core sending the wakeup is running at many times the
speed of the core halting, but it has been observed on an Intel Icelake
mobile processor.
This reduces the number of instructions between decrementing the count
and halting in the halt wait case. Use the same code for the spin wait
case for consistency.
Using Interrupt On Completion is not robust, because the interrupt flag
is also set if a short transfer is detected. So we need to poll the
Active flag in the transfer descriptors.
The XHCI device index and scratchpad buffers are mapped into high memory,
in order to conserve low memory. They need to be accessible in the virtual
address space to allow us to initialise them. After initialisation. only
the XHCI accesses them.
We also only need to access the data structures in the device private
workspace during initialisation, but keeping separate physical and virtual
addresses for these structures makes the code considerably more complex,
so for now, move these to low memory.
The old barrier implementation was very slow when running on a multi-socket
machine (pcmemtest issue 16).
The new implementation provides two options:
- when blocked, spin on a thread-local flag
- when blocked, execute a HLT instruction and wait for a NMI
The first option might be faster, but we need to measure it to find out. A
new boot command line option is provided to select between the two, with a
third setting that uses a mixture of the two.
