On 08/04/14 18:52, Russell King - ARM Linux wrote:

On Tue, Aug 05, 2014 at 12:36:49AM +0800, Fu, Zhonghui wrote:

quoted

Hi, Arend

I investigated this issue, and its root cause is still that sdio
controller can't receive interrupts from WiFi chip on sdio bus when
sdio controller is in runtime suspend status. I am running 3.16-rc5
linux kernel on ASUS T100TA tablet, and using sdhci-acpi driver.

That's the root cause.  I fixed this with the Freescale i.MX SD driver
which is now able to report pending SDIO interrupts while runtime PM
suspended.

Other host drivers probably need fixing too, or having runtime PM
disabled on them - if you can't receive SDIO interrupts while runtime
PM suspended, then entering runtime PM while you have a SDIO device
attached is a bug.

This is something for the MMC people to deal with rather than Arend.

Occasionally, the itch is there to fix mmc code, but this looks a bit 
tricky. The fun starts in sdio.c:mmc_attach_sdio():

	/*
	 * Enable runtime PM only if supported by host+card+board
	 */
	if (host->caps & MMC_CAP_POWER_OFF_CARD) {
		/*
		 * Let runtime PM core know our card is active
		 */
		err = pm_runtime_set_active(&card->dev);
		if (err)
			goto remove;

		/*
		 * Enable runtime PM for this card
		 */
		pm_runtime_enable(&card->dev);
	}

The comment above the if statement seems to be stating the right idea, 
but the code only looks at the host controller capability flags.

Regards,
Arend