sdhci: Try to complete the last transaction if dumping

If the kernel panics while a thread is in the middle of an SDHCI
transaction, trying to dump to a dump target on the MMC would result in
a hang.  Fix this by completing the transaction first.

Reviewed by:	imp
Obtained from:	Hewlett Packard Enterprise
Differential Revision:	https://reviews.freebsd.org/D54255

1 files changed, 12 insertions, 0 deletions

diff --git a/sys/dev/sdhci/sdhci.c b/sys/dev/sdhci/sdhci.c
index b53b85bf44c2..0426d9d27916 100644
--- a/sys/dev/sdhci/sdhci.c
+++ b/sys/dev/sdhci/sdhci.c
@@ -2183,6 +2183,18 @@ sdhci_generic_acquire_host(device_t brdev __unused, device_t reqdev)
 	int err = 0;
 
 	SDHCI_LOCK(slot);
+	/*
+	 * If the bus is busy at dump time, it may have stopped in the middle of
+	 * a transaction.  Try to complete that transaction before continuing.
+	 */
+	if (slot->bus_busy && dumping) {
+		SDHCI_UNLOCK(slot);
+		while (slot->req != NULL) {
+			sdhci_generic_intr(slot);
+			DELAY(10);
+		}
+		return (0);
+	}
 	while (slot->bus_busy)
 		msleep(slot, &slot->mtx, 0, "sdhciah", 0);
 	slot->bus_busy++;