k2 816 core2x: most significant bit of joystick bytes flapping (work-around in kernel)

[ghackwrench]

See below for the issue details.

Hardware version

• Machine type: Wildbits/K2
• PCB revision: purple board (?)
• CPU: 65816
• Speed: 2x

[ghackwrench]

When reading the CIA ports associated with the joystics ($dc00 and $dc01), the high-bit is unstable. As a result, the kernel was queuing countless bogus joystick events. A work-around was applied in kbd_f256k2.asm (the high-bit is forced to 1). It is unknown if this only affects optical keyboard systems.

[mbrukner]

This should now be fixed.

Root cause: only one of the ports was affected — bit 7 was used in older Gen1 designs as part of the keyboard matrix. With the optical keyboard, that connection was removed, leaving bit 7 floating.

The fix ties bit 7 to logic-high in 02020000.

Please let me know if you can still reproduce the issue.