On 23/09/2014 12:20 p.m., Ulf Hansson wrote:
On 22 September 2014 12:09, Roger Tseng <rogerable@xxxxxxxxxxx> wrote:
On Thu, 2014-09-18 at 23:14 +0200, Ulf Hansson wrote:
[...]
In that case, don't forget to enable MMC_CAP2_FULL_PWR_CYCLE.
if MMC_CAP2_NO_PRESCAN_POWERUP enable, will call mmc_power_off() at start,
then it will check ios.power_mode, but the state is MMC_POWER_OFF and just
return.
Uhh, that's right! So, I wonder why we invokes mmc_power_off() from
that path at all.
Hmm, I think we should change the behavior in mmc_start_host(), like below:
1) Add a "MMC_POWER_UNDEFINED" state which is what the power state
should be assigned to at allocation.
2 ) From mmc_start_host(), invoke mmc_power_off() when
MMC_CAP2_NO_PRESCAN_POWERUP and MMC_CAP2_FULL_PWR_CYCLE is set.
Would that work?
Yes. I have confirmed this by following changes. The MMC_POWER_UNDEFINED
designation in mmc_start_host() will eventually cause a power-off
operation.
But I wonder if we need to additionally check MMC_CAP2_FULL_PWR_CYCLE
before calling mmc_power_off()?
The intent from my side was to keep the current behaviour for those
that already used MMC_CAP2_NO_PRESCAN_POWERUP, but it's s not a big
deal.
I checked the log and found the commit that invokes mmc_power_off():
a08b17be8b984a7c51cd5a480cd977363df353f9
0d3e3350d5871c53464be4c92d57198744247005
(https://www.mail-archive.com/linux-mmc@xxxxxxxxxxxxxxx/msg19638.html )
The proposed change might bring back some delay since invoking
mmc_power_off() in mmc_start_host() is more than NOP now and triggers
real power-off and re-init in sdhci.
Actually the above commits was added due to the below commit:
fa5501890d8974301042e0202d342a6cbe8609f4
But the commits you refer to, didn't bring back the old behaviour,
which I think was the intent. Instead we added a NOP call to
mmc_power_off() from mmc_start_host().
We have few options on how to go forward, but let's loop in Adrian
Hunter first, since he might be able to comment on this as well.
Having mmc_power_off() in mmc_start_host()
actually power off should be OK.
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