On 07/07/2010 04:52 PM, ext Nicolas Pitre wrote:
On Wed, 7 Jul 2010, Roger Quadros wrote:
On 07/06/2010 08:42 PM, ext Nicolas Pitre wrote:
On Tue, 6 Jul 2010, Roger Quadros wrote:
OK, this is how I see it.
- Treat the non-removable card as non-removable. So no need to do card
detect
emulation.
- Treat the GPIO power enable on wl1271 as VMMC supply. Use fixed
regulator
framework to define this regulator& supply. Even though you mention that
it
is not actually a supply, it fits well in the fixed supply framework.
- When the host controller is enumerated, the mmc core will power up the
slot,
find the sdio card, and probe the function driver (i.e. wl1271_sdio).
- if interface is not in use, the function driver must release the sdio
host,
and this should eventually disable the vmmc supply.
- Whenever the wlan interface must be brought up, wl1271_sdio, can claim
the
sdio host. this will cause the vmmc supply to be enabled, for as long as
the
interface is up.
Does this address all issues?
This is mostly all good, except that claiming/releasing the SDIO host is
about access to the bus. It must be claimed right before doing any IO,
and released right after that, even when the card is expected to remain
powered. This is not the proper place to hook power control.
Agreed, but is it so that SDIO power may be removed between a host_release and
claim? This appears so from omap_hsmmc host controller.
No, it is not because a host is not claimed that power should be
dropped. The host claim/release is meant to provide exclusive access to
the card that's all.
If the OMAP controller is dropping power to the card upon
host->disable() then it is wrong. AFAICS only the OMAP controller is
playing such games at the moment and I suspect the semantics might not
be all right. Shutting down the _controller_ when it is idle might be a
good thing, but not power to the _card_. Only the function driver might
know when it is fine to lose power.
I completely agree with you Nicolas. omap_hsmmc needs to be fixed so that it
does not control MMC/SDIO slot supply voltage. It should deal with only the mmc
controller power savings and not the card/function power savings.
regards,
-roger
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