mmc: sdio: reset card during power_restore

mmc_sdio_power_restore() skips some steps that are performed in other
power-related codepaths which are necessary to fully reset the card.
Without this, runtime PM fails for SD8686 SDIO wifi on OLPC XO-1.5.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/core/sdio.c

@@ -691,15 +691,54 @@ static int mmc_sdio_resume(struct mmc_host *host)
 static int mmc_sdio_power_restore(struct mmc_host *host)
 {
 	int ret;
+	u32 ocr;
 
 	BUG_ON(!host);
 	BUG_ON(!host->card);
 
 	mmc_claim_host(host);
+
+	/*
+	 * Reset the card by performing the same steps that are taken by
+	 * mmc_rescan_try_freq() and mmc_attach_sdio() during a "normal" probe.
+	 *
+	 * sdio_reset() is technically not needed. Having just powered up the
+	 * hardware, it should already be in reset state. However, some
+	 * platforms (such as SD8686 on OLPC) do not instantly cut power,
+	 * meaning that a reset is required when restoring power soon after
+	 * powering off. It is harmless in other cases.
+	 *
+	 * The CMD5 reset (mmc_send_io_op_cond()), according to the SDIO spec,
+	 * is not necessary for non-removable cards. However, it is required
+	 * for OLPC SD8686 (which expects a [CMD5,5,3,7] init sequence), and
+	 * harmless in other situations.
+	 *
+	 * With these steps taken, mmc_select_voltage() is also required to
+	 * restore the correct voltage setting of the card.
+	 */
+	sdio_reset(host);
+	mmc_go_idle(host);
+	mmc_send_if_cond(host, host->ocr_avail);
+
+	ret = mmc_send_io_op_cond(host, 0, &ocr);
+	if (ret)
+		goto out;
+
+	if (host->ocr_avail_sdio)
+		host->ocr_avail = host->ocr_avail_sdio;
+
+	host->ocr = mmc_select_voltage(host, ocr & ~0x7F);
+	if (!host->ocr) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	ret = mmc_sdio_init_card(host, host->ocr, host->card,
 				mmc_card_keep_power(host));
 	if (!ret && host->sdio_irqs)
 		mmc_signal_sdio_irq(host);
+
+out:
 	mmc_release_host(host);
 
 	return ret;