At the moment the PS7 is using three PLLs to generate its clocking tree.
One for the DDR, one for the ARM and one for the IO. This allows to run all
components at their respective maximum clock and extract maximum
performance from all components.
With some slight modifications it is possible to trade maximum performance
for a reduction in power consumption by using the same PLL for all three
sets of components and disabling the other two PLLs.
The CPU is now running at 500MHz rather than 666MHz and the DDR memory at
500MHz rather than 533MHz. This reduces power consumption by ~125mW.
This is OK since neither of them is a bottleneck for overall system
performance.
In addition software will downclock the CPU to 250MHz when full performance
is not required.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
The 200 MHz clock was only used as the IODELAY controller clock. Since the
design does not use any IODELAYs anymore this clock can be removed.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
The debug register logic for the DMA take up a fair amount of resources.
Disabling them frees up space in the FPGA and also helps a bit with power.
Since those registers are mainly useful in development and not so much in
production the change shouldn't have any visible external effects.
It is possible to re-enable the debug registers by setting DEBUG_BUILD=1.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
AndreiGrozav
Adrian Costina
Lars-Peter Clausen