mmc: Speed up reboot with an absent card

On devices with no card detect mechanism, the host ends up polling for
the insertion of a card. This polling happens at multiple frequencies
and with many steps (SDIO, SD, MMC), some of which involve timeouts.
If a reboot is requested during one of those scans, it will stall,
pointlessly, for up to a minute while it completes.

Attempt to short circuit the rescan if the MMC interface is being
removed.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

Author: pelwell

drivers/mmc/core/core.c

@@ -399,10 +399,16 @@ void mmc_wait_for_req_done(struct mmc_host *host, struct mmc_request *mrq)
 	struct mmc_command *cmd;
 
 	while (1) {
-		wait_for_completion(&mrq->completion);
+		if (!host->rescan_disable)
+			wait_for_completion(&mrq->completion);
 
 		cmd = mrq->cmd;
 
+		if (host->rescan_disable) {
+			cmd->error = -ENOENT;
+			break;
+		}
+
 		if (!cmd->error || !cmd->retries ||
 		    mmc_card_removed(host->card))
 			break;
@@ -619,6 +625,11 @@ EXPORT_SYMBOL(mmc_is_req_done);
  */
 void mmc_wait_for_req(struct mmc_host *host, struct mmc_request *mrq)
 {
+	if (host->rescan_disable) {
+		mrq->cmd->error = -ENOENT;
+		return;
+	}
+
 	__mmc_start_req(host, mrq);
 
 	if (!mrq->cap_cmd_during_tfr)
@@ -2265,6 +2276,8 @@ void mmc_rescan(struct work_struct *work)
 
 	for (i = 0; i < ARRAY_SIZE(freqs); i++) {
 		unsigned int freq = freqs[i];
+		if (host->rescan_disable)
+			return;
 		if (freq > host->f_max) {
 			if (i + 1 < ARRAY_SIZE(freqs))
 				continue;

drivers/mmc/core/mmc_ops.c

@@ -512,6 +512,9 @@ int __mmc_poll_for_busy(struct mmc_host *host, unsigned int period_us,
 
 	timeout = jiffies + msecs_to_jiffies(timeout_ms) + 1;
 	do {
+		if (host->rescan_disable)
+			return -ENOENT;
+
 		/*
 		 * Due to the possibility of being preempted while polling,
 		 * check the expiration time first.

drivers/mmc/core/sdio.c

@@ -673,6 +673,10 @@ static int mmc_sdio_init_card(struct mmc_host *host, u32 ocr,
 		ocr |= R4_18V_PRESENT;
 
 try_again:
+	if (host->rescan_disable) {
+		err = -ENOENT;
+		goto remove;
+	}
 	if (!retries) {
 		pr_warn("%s: Skipping voltage switch\n", mmc_hostname(host));
 		ocr &= ~R4_18V_PRESENT;