+Grygorii Strashko
On 25 April 2017 at 08:21, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> On 24/04/17 23:33, Ulf Hansson wrote:
>> On 21 April 2017 at 12:08, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>>> The SDIO card state might be being preserved during hibernation, for
>>> example a SDIO wifi card supporting WOWLAN. That state will be lost if an
>>> SDIO reset is done. One way to avoid that would be to build mmc core as a
>>> module and simply not load it until after attempting to restore the
>>> hibernation image. However that won't work if the hibernation image is
>>> stored on eMMC which, of course, requires mmc core.
>>
>> I don't follow here. Are you saying the SDIO card is kept powered in
>> hibernation, as to be able to support WOWLAN, right?
>
> Yes
Okay, makes sense!
>
>>
>> Then, it feels plain wrong the mmc_rescan() tries to re-initialize it.
>> That should never happen, unless something is broken of course.
>
> The thing to note about hibernation is that there is a regular boot in
> between saving the hibernation image and restoring it again. At boot time,
> the kernel knows almost nothing about whether there is a hibernation image
> and whether or not it will be restored. Consequently it becomes difficult
> to avoid mmc_rescan(). As mentioned above, we need mmc_rescan() to
> initialize the eMMC so that the hibernation image can be read.
What's wrong with using the hibernation callbacks in the struct
dev_pm_ops? We already do this.
To manage the eMMC/SD/SDIO card device, we do this in /drivers/mmc/core/bus.c:
static const struct dev_pm_ops mmc_bus_pm_ops = {
SET_RUNTIME_PM_OPS(mmc_runtime_suspend, mmc_runtime_resume, NULL)
SET_SYSTEM_SLEEP_PM_OPS(mmc_bus_suspend, mmc_bus_resume)
};
To mange the sdio func device, we do this in /drivers/mmc/core/sdio_bus.c
static const struct dev_pm_ops sdio_bus_pm_ops = {
SET_SYSTEM_SLEEP_PM_OPS(pm_generic_suspend, pm_generic_resume)
SET_RUNTIME_PM_OPS(
pm_generic_runtime_suspend,
pm_generic_runtime_resume,
NULL
)
};
In other words, we are re-using the same callbacks for system PM
suspend as for system PM hibernation.
I do imagine there are something broken for SDIO in this path, mainly
because I haven't heard much from people using it.
However, for (e)MMC/SD card point of view, restoring from hibernation
should work. I remember that Grygorii Strashko has been working on
this, perhaps he can confirm some of his observations.
Kind regards
Uffe
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
