Hello,
Our target wakes on the FEC interrupt when returning from wait mode. We would it to wake on FEC interrupt from stop mode. This doesn't seem to work. After reviewing the RM, I believe this is because the AHB bus clocks are off.
The FEC has two clocks enabled by default (AHB and IPG). I'm having a hard time understanding what the IPG bus is. My motivation is to configure the IP bus such that we can wake on an FEC interrupt in stop mode. Is this possible?
Thanks!
Stephen
P.S. An image of the iMX25 clock tree will be worth it's weight in gold!
Solved! Go to Solution.
Hello,
In Stop mode—all PLLs and all clocks are shut down. FEC does not have special
(static or 32KHz ) wake up option.
Have a great day,
Yuri
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Hello,
In Stop mode—all PLLs and all clocks are shut down. FEC does not have special
(static or 32KHz ) wake up option.
Have a great day,
Yuri
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------
Yuri,
Thanks for your prompt reply. Is it possible to wake from DOZE mode via an FEC interrupt? It didn't appear to work after setting the bits in the clock gating control registers for hclk_fec and ipg_clk_fec.
Hello,
In Doze mode ARM platform clock is off and all the other modules are off,
this means FEC interrupts cannot be served (as wake up events).
Wait mode can be used with FEC interrupts (as wake up events).
Regards,
Yuri.
Yuri,
Thanks for that clarification. I need to be able to explain why the FEC interrupt cannot wake the core from Doze mode in more detail. Please forgive my persistence.
The platform clock is certainly off in Doze mode. According to table 8-1 in the reference manual, "all other modules are optionally disabled" for Doze mode. Are we referring to the same document (i.MX25 reference manual)?
Here is what I understand. Perhaps you will be kind enough to help me fill in the blanks, and confirm/reject the following.
This information, alone, doesn't tell me why FEC interrupts "cannot be served (as wake up events)". Perhaps you will be kind enough to help me fill in the blanks.
Thanks,
Stephen
Hello,
1.
Correct, if FEC module clocks are not gated, assuming FEC is working in DOZE mode, its interrupts can
be used for wake up.
2.
Note, although FEC is shown on Figure 1-1 as SDMA peripherals, this only means, that in general SDMA
can serve FEC requests. But FEC has own DMA , that is more effective.
Regards,
Yuri.