Because pre-v6 ARM lacks support for an atomic compare-and-swap, we
implement _lock_cas() as a restartable atomic squence that is checked
in the IRQ handler right before AST processing. (This is safe because,
for all practical purposes, there are no SMP pre-v6 ARM systems.)
This can serve as a model for other non-MP platforms that lack the
necessary atomic operations for mutexes (SuperH, for example).
Upshots of this change:
- kmutex_t is now down to 8 bytes on ARM; about as good as we can get.
- ARM2 systems don't have to trap and emulate SWP or SWPB for mutexes.
The acorn26 port is not updated by this commit to do the LOCK_CAS_CHECK.
That is left as an exercise for the port maintainer.
Reviewed and tested by Matt Thomas.
Includes drivers for I2C, I2S, PCMCIA controller, USB device controller,
OHCI USB controller (from OpenBSD) and some improvements to the LCD
controller driver.
devices hooked up to the HPI pin.
HPIs cannot be masked at the interrupt controller; they can only be masked
by disabling IRQs in the XScale core. To deal with this, we tweak the
interrupt frame so that IRQs are disabled when the interrupt dispatcher
returns due to a masked HPI interrupt. IRQs will be re-enabled by a
subsequent splx(9).
Fortunately the only instance where HPI is used is for the console UART
on a couple of boards, so this hack does not adversely affect performance.
Contributed by Wasabi Systems.
This allows us to convert aucom to just another com attachment, and cleanup
some code in the com_arbus.c.
Additionally, we use a common com_cleanup routine rather than having a
zillion copies of it in the attachment points.
This has been tested on a number architectures, and it has been shown to get
close to comparable performance when COM_REGMAP is defined, and comparable
when it is not defined.
Approved by core@. Fixes PR port-evbmips/32362.
to the screen on which they are being called. The driver cannot guess
this by itself but it is needed to implement, at least, the getwschar and
putwschar functions in the correct place. There are no functional changes
yet.
Tested on i386 (vga, vga_raster, machfb, vesafb), macppc and sparc64.
Suggested and reviewed by macallan@.
nonaka