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>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
index 4d0c15bfa514..262fff019177 100644
--- a/drivers/mmc/core/sdio.c
+++ b/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;