Suspend of SDIO function devices

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Hi,

I'm currently looking into the suspend callbacks of drivers of hardware that use an SDIO interface, specifically the libertas_sdio driver:

   drivers/net/wireless/marvell/libertas/if_sdio.c

The comments in if_sdio_suspend() suggest that by returning -ENOSYS due to runtime-dependant circumstances, the MMC core will remove the card entirely at suspend time. I then searched for the bits that do that and failed, until I came across this old commit, which first appeared in 3.16:

573185cc7e6 mmc: core: Invoke sdio func driver's PM callbacks from the sdio bus

Before that commit, the mmc core did in fact invoke the card's .suspend() callback manually and if it returned a non-zero result, it would remove the card. Now that the generic pm functions are in place, this does no longer happen because the host and its clients are independent entities. Consequently, systems fail to suspend when the libertas_sdio module is loaded.

The pm notifier code in drivers/mmc/core/core.c does still handle cases where no pm functions are provided at all (in which case it removes the card), but it doesn't handle -ENOSYS return values at runtime.

Now I'm wondering how this is supposed to work, and which end needs fixing. The mmc/sdio core by restoring the old logic from before 573185cc7e6, or the libertas driver.

The platform I'm working on does not retain power for the SDIO slaves, so a complete re-init is necessary after resume.

Please advise, I'm happy to test approaches and send patches.


Thanks,
Daniel

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