Nicolas Pitre wrote:
On Tue, 6 Jul 2010, Roger Quadros wrote:
On 07/06/2010 03:53 PM, ext Ohad Ben-Cohen wrote:
Hi Roger,
On Tue, Jul 6, 2010 at 1:35 PM, Roger Quadros<roger.quadros@xxxxxxxxx>
wrote:
My point is that shouldn't this be handled by SDIO core?
Care to explain what you mean / give a code example ?
If the Power enable GPIO can be treated as SDIO slot supply (i.e. vmmc), then
the SDIO/MMC core should tackle it, just like it deals with supply for slots
with removable cards.
Exact.
You need card detect events in order to trigger card& sdio function
initialization and removals.
Why would you trigger function initialization and removal? Just to turn
off power? That's a bit like pulling off the battery from your laptop
when you want to suspend it. There is a better way to go about things.
Please share any alternative approach you may be thinking on.
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.
Another function pair would be needed instead, which would do almost
like the suspend/resume code is already doing. Something like:
/*
* Indicate to the core SDIO layer that we're not requiring that the
* function remain powered. If all functions for the card are in the
* same "no power" state, then the host controller can remove power from
* the card. Note: the function driver must preserve hardware states if
* necessary.
*/
int sdio_release_power(struct sdio_func *func);
/*
* Indicate to the core SDIO layer that we want power back for this
* SDIO function. The power may or may not actually have been removed
* since last call to sdio_release_power(), so the function driver must
* not assume any preserved state at the hardware level and re-perform
* all the necessary hardware config. This function returns 0 when
* power is actually restored, or some error code if this cannot be
* achieved. One error reason might be that the card is no longer
* available on the bus (was removed while powered down and card
* detection didn't trigger yet).
*/
int sdio_claim_power(struct sdio_func *func);
That's it. When the network interface is down and the hardware is not
needed, you call sdio_release_power(). When the request to activate the
network interface is received, you call sdio_claim_power() and configure
the hardware appropriately. If sdio_claim_power() returns an error,
then you just return an error to the network request, and eventually the
driver's remove method will be called if this is indeed because the card
was removed.
In the core SDIO code, this is almost identical to a suspend/resume
request, except that the request comes from the function driver instead
of the core MMC code.
For eMMC in omap_hsmmc, this is all done via claim_host / release_host
which call ->enable() / ->disable() methods. omap_hsmmc makes use of
mmc_power_restore_host() which calls host->bus_ops->power_restore()
which is not implemented for SDIO, but for MMC and SD it reinitializes
the card.
Set omap2_hsmmc_info mmc[x] {.nonremovable=true, .power_saving=true} and
implement host->bus_ops->power_restore() for SDIO, then the power will
go off 9 seconds after sdio_release_host() is called. Then tweak omap_hsmmc
so that it doesn't wait 9 seconds for the SDIO case
Nicolas
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