board: 8064: storage: vote against IDLE power collapse
During the SDCC DMA transfer, if DMA transfer time is
long enough to do IDLE power collapse then system may
go into IDLE power collapse and once SDCC DMA transfer
is completed, system wakes up from Idle Power Collapse
due to SDCC DMA interrupt. But delay for waking up
from Idle Power collapse could be as large as 5 ms which
really degrades the overall read & write throughputs
for SD/eMMC/SDIO cards.
For example, following are the performance numbers with
eMMC card on MSM8960 platform with and without Idle Power
Collapse.
Idle Power collapse enabled:
LMDD Read throughput = ~14 MB/s
LMDD Write throughput = ~6 MB/s
Idle Power Collapse disabled:
LMDD Read throughput = ~25 MB/s
LMDD Write throughput = ~8 MB/s
So this change votes against the Idle power collapse by registering
with PM QOS about it's acceptable DMA latency when SDCC transfer is
active. This latency value is one more than the latency of SWFI
which means system can go into SWFI but not in any of the other
low power modes (including Idle power collapse).
Change-Id: I8740dd5bb86fe8cfbf6a294850d378a3c6692f40
Signed-off-by: Oluwafemi Adeyemi <aadeyemi@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
3 files changed