svn commit: r185623 - head/sys/dev/pccbb

[Warner Losh]

Author: imp
Date: Fri Dec  5 04:46:26 2008
New Revision: 185623
URL: http://svn.freebsd.org/changeset/base/185623

Log:
  Augment comments, and move things around a smidge.

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

Modified: head/sys/dev/pccbb/pccbb.c
==============================================================================
--- head/sys/dev/pccbb/pccbb.c	Fri Dec  5 04:43:25 2008	(r185622)
+++ head/sys/dev/pccbb/pccbb.c	Fri Dec  5 04:46:26 2008	(r185623)
@@ -946,32 +946,32 @@ cbb_cardbus_reset(device_t brdev, device
 
 	/*
 	 * Asserting reset for 20ms is necessary for most bridges.  For some
-	 * reason, the Ricoh RF5C47x bridges need it asserted for 400ms.
+	 * reason, the Ricoh RF5C47x bridges need it asserted for 400ms.  The
+	 * root cause of this is unknown, and NetBSD does the same thing.
 	 */
 	delay = sc->chipset == CB_RF5C47X ? 400 : 20;
 	PCI_MASK_CONFIG(brdev, CBBR_BRIDGECTRL, |CBBM_BRIDGECTRL_RESET, 2);
 	pause("cbbP3", hz * delay / 1000);
 
 	/*
-	 *  If a card exists and we're turning it on, take it out of reset.
+	 * If a card exists and we're turning it on, take it out of reset.
+	 * After clearing reset, wait up to 1.1s for the first configuration
+	 * register (vendor/product) configuration register of device 0.0 to
+	 * become != 0xffffffff.  The PCMCIA PC Card Host System Specification
+	 * says that when powering up the card, the PCI Spec v2.1 must be
+	 * followed.  In PCI spec v2.2 Table 4-6, Trhfa (Reset High to first
+	 * Config Access) is at most 2^25 clocks, or just over 1s.  Section
+	 * 2.2.1 states any card not ready to participate in bus transactions
+	 * must tristate its outputs.  Therefore, any access to its
+	 * configuration registers must be ignored.  In that state, the config
+	 * reg will read 0xffffffff.  Section 6.2.1 states a vendor id of
+	 * 0xffff is invalid, so this can never match a real card.  Print a
+	 * warning if it never returns a real id.  The PCMCIA PC Card
+	 * Electrical Spec Section 5.2.7.1 implies only device 0 is present on
+	 * a cardbus bus, so that's the only register we check here.
 	 */
 	if (on && CBB_CARD_PRESENT(cbb_get(sc, CBB_SOCKET_STATE))) {
 		/*
-		 * After clearing reset, wait up to 1.1s for the first
-		 * configuration register (vendor/product) configuration
-		 * register of device 0.0 to become != 0xffffffff.  The PCMCIA
-		 * PC Card Host System Specification says that when powering
-		 * up the card, the PCI Spec v2.1 must be followed.  In PCI
-		 * spec v2.2 Table 4-6, Trhfa (Reset High to first Config
-		 * Access) is at most 2^25 clocks, or just over 1s.  Section
-		 * 2.2.1 states any card not ready to participate in bus
-		 * transactions must tristate its outputs.  Therefore, any
-		 * access to its configuration registers must be ignored.  In
-		 * that state, the config reg will read 0xffffffff.  Section
-		 * 6.2.1 states a vendor id of 0xffff is invalid, so this can
-		 * never match a real card.  Print a warning if it never
-		 * returns a real id.  The PCMCIA PC Card Electrical Spec
-		 * Section 5.2.7.1 implies only device 0.
 		 */
 		PCI_MASK_CONFIG(brdev, CBBR_BRIDGECTRL,
 		    &~CBBM_BRIDGECTRL_RESET, 2);