Re: [PATCH] sdhci: wakeup from runtime PM

Ulf Hansson
2016-04-08T20:51:51Z

On 8 April 2016 at 17:19, Alan Stern <stern@rowland.harvard.edu> wrote:
> On Fri, 8 Apr 2016, Ulf Hansson wrote:
>
>> From power consumption point if view we already discussed this
>> particular case in an earlier thread, but let me elaborate what I
>> think one more time:
>>
>> Now, this is relevant for removable cards lacking GPIO card detect, as
>> for other cases and non-removable cards I think we are in agreement
>> that their is no issue from power consumption point of view, right!?
>>
>> 1. The current solution:
>> - Use MMC_CAP_NEEDS_POLL which makes the mmc core to re-schedule a
>> work once every second to poll for a card (Why is it one second? Could
>> we perhaps have that configurable?).
>
> The block layer handles media polling for removable block devices, and
> it is configurable. For example, /sys/block/sr0/events_poll_msecs can
> be set to control how often the system polls for a disc in my DVD
> drive.
>
> Does MMC do its own polling separate from the block layer? If so, why?

Good question. Probably because of legacy or perhaps to deal with corner cases.

When I get some spare bandwidth I will check to see if it makes sense
to convert MMC polling to the block layer polling.

Kind regards
Uffe