The _Watchdog_Nanoseconds_since_tick_handler() function caller does
not take into account that the timer counter may wrap, underflow or
overflow. Instead, the driver must take that into account. This
GPTIMER DrvMgr driver patch makes use of the IRQ-Pending bit to
determine if a underflow has happened. In that case a greater time
than one tick is returned (even considering the function name..).
The TLIB clock layer must also ACK the interrupt pending bit,
otherwise we couldn't determine whether an IRQ is pending or if
belongs to un old already handled tick IRQ.
Note that this patch only fixes the DrvMgr GPTIMER driver and TLIB,
the standard LEON3 GPTIMER driver still needs a fix.
With this patch the LEON family can access the GRLIB GPTIMER using
the Timer library (TLIB).
A System Clock driver instead of BSP/clock/ck_init.c is provided
using the TLIB. The classic clock driver is split in two parts,
clock driver and timer driver. The BSPs need only to fullfill the
timer interface instead of the clock interface. Currently only
LEON3 uses it. The LEON2 Timer is not ported to TLIB.
The GPTIMER driver is implemented using the Driver Manager, so the
System Clock Driver is at this point only suitable for LEON3 when
the driver manager is initialized during BSP startup. When the DrvMgr
is not initialized during startup the standard BSP/clock dirver is
used.
LEON2 sometimes also needs to access GPTIMER when a off-chip GRLIB AMBA
systems is connected, for example AMBA-over-PCI.
