svn commit: r261940 - head/sys/dev/sdhci

[Ian Lepore]

Author: ian
Date: Sat Feb 15 17:59:32 2014
New Revision: 261940
URL: http://svnweb.freebsd.org/changeset/base/261940

Log:
  Increase the wait time for acquiring the bus from 10 to 250ms.
  
  Normally it never needs to wait here at all; waiting is done at the end
  of the prior command.  When doing a crash dump, the normal interrupt
  mechanism isn't used; instead the interrupt handler is called repeatedly
  in a polling-like manner.  This can subvert hardware-specific drivers
  and lead to trying to start a new command while the previous command is
  still busy on the bus.  Since the SD spec says the longest a card can
  take to execute any command is 250ms, use that as a timeout.

Modified:
  head/sys/dev/sdhci/sdhci.c

Modified: head/sys/dev/sdhci/sdhci.c
==============================================================================
--- head/sys/dev/sdhci/sdhci.c	Sat Feb 15 17:55:35 2014	(r261939)
+++ head/sys/dev/sdhci/sdhci.c	Sat Feb 15 17:59:32 2014	(r261940)
@@ -767,8 +767,17 @@ sdhci_start_command(struct sdhci_slot *s
 	/* We shouldn't wait for DAT for stop commands. */
 	if (cmd == slot->req->stop)
 		mask &= ~SDHCI_DAT_INHIBIT;
-	/* Wait for bus no more then 10 ms. */
-	timeout = 10;
+	/*
+	 *  Wait for bus no more then 250 ms.  Typically there will be no wait
+	 *  here at all, but when writing a crash dump we may be bypassing the
+	 *  host platform's interrupt handler, and in some cases that handler
+	 *  may be working around hardware quirks such as not respecting r1b
+	 *  busy indications.  In those cases, this wait-loop serves the purpose
+	 *  of waiting for the prior command and data transfers to be done, and
+	 *  SD cards are allowed to take up to 250ms for write and erase ops.
+	 *  (It's usually more like 20-30ms in the real world.)
+	 */
+	timeout = 250;
 	while (state & mask) {
 		if (timeout == 0) {
 			slot_printf(slot, "Controller never released "