Hi Sekhar
Nori, Sekhar wrote:
Hi James,
On Tue, Feb 09, 2010 at 21:51:01, James Nuss wrote:
Hi,
I have discovered a bug in the cpuidle code for the OMAP-L13x (da8xx)
platform.
In the state described as "WFI and DDR Self-Refresh", the code is
actually putting the DDR into the "Power Down" mode which is not the
same as self-refresh.
So the description string should read "WFI and DDR Power Down".
Yes, going into power down on OMAP-L138 was intentional (it is
supposed to save more power than self-refresh). I agree the state
description could have been conditional on pdata->ddr2_pdown value.
Putting the DDR into self-refresh and subsequently gating the clocks for
greater power savings, requires significantly more work (Refer to
Section 2.16 OMAP-L1x DDR2/mDDR Memory Controller User's Guide).
This is implemented as part of suspend-to-RAM support. Have a look at
arch/arm/mach-davinci/pm.c file.
I see. So is the DDR self-refresh only feasible as a suspend-to-RAM
option? i.e. Is it too slow to enter/exit to use in a running state?
I have successfully put the board to sleep using:
echo mem >/sys/power/state
But how do you resume from this suspended state? Do all peripherals have
support for resuming from suspend right now?
Thanks,
James
Thanks,
Sekhar
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