AT91 VAR HAL extensions

[Andrew Lunn <andrew at lunn dot ch>]

Hi Folks

Attached is a patch which extends the AT91 varient HAL.

The newer AT91 devices have a system controller. This contains a
number of new devices: 

A simple UART designed specifically for debugging
Periodic Interval Timer designed to provide the OS tick
Watchdog timer
Reset Controller
Power Management controller
A Real Time Timer

For a start this patch adds register definitions of these new devices.

The patch also adds support for the debug serial port. Via CDL this
device can be used for hal diag instead of using the AT91 USARTs.
(I've not tested ^C support, so it might not work).

Similarly, via CDL it is possible to use the Periodic Interval Timer
to generate the eCos tick instead of using a Timer Counter. When this
option is enabled hal_delay_us also uses the PIT so saving another TC.

By default the old behaviour is retained, so you need to specifically
enable these new features if you want to use them. The specific HAL
must also implement the require interface to indicate the chip has the
necassary hardware.

The devices in the system controller all share one interrupt in the
Advanced Interrupt Controller. So i've added code to demultiplex this
interrupt into an interrupt per device. What is not nice is that there
is no easy way to determine which device in the system controller
caused the interrupt so it is necassary to check each device in turn
to find the once which caused the interrupt. Since there is no second
level interrupt controller it is also not possible to disable/enable
individual interrupts. So when you mask one of these interrupts by
calling hal_interrupt_mask() it actually masks the whole system
controller. So you have to take this into account when writing device
drivers for the system controller devices. This is only compiled if
CYGINT_HAL_ARM_AT91_SYS_INTERRUPT is defined so older targets won't
get it.

If the reset controller exists this will be used to implement
hal_at91_reset_cpu() rather than using the watchdog. The watchdog in
the system controller is different to the watchdog in older devices so
the old code does not work with the new watchdog controller.

Some of this code is by Oliver Munz. Thanks Oliver.

        Andrew

Attachment: hal.arm.at91.var.diff
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