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From: Sepherosa Ziehau <sephe@FreeBSD.org>
Date: Tue, 27 Sep 2016 06:00:10 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r306359 - head/sys/dev/pci
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Author: sephe
Date: Tue Sep 27 06:00:10 2016
New Revision: 306359
URL: https://svnweb.freebsd.org/changeset/base/306359

Log:
  pci: Clear the MEM/PORT_EN bit when updating PCI BAR
  
  It's unsafe to update the BAR when the related EN bit is set.
  
  Submitted by:	Dexuan Cui <decui microsoft com>
  Reviewed by:	jhb
  MFC after:	1 week
  Sponsored by:	Microsoft
  Differential Revision:	https://reviews.freebsd.org/D7914

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

Modified: head/sys/dev/pci/pci.c
==============================================================================
--- head/sys/dev/pci/pci.c	Tue Sep 27 00:53:41 2016	(r306358)
+++ head/sys/dev/pci/pci.c	Tue Sep 27 06:00:10 2016	(r306359)
@@ -5000,6 +5000,7 @@ pci_reserve_map(device_t dev, device_t c
 	struct resource_list *rl = &dinfo->resources;
 	struct resource *res;
 	struct pci_map *pm;
+	uint16_t cmd;
 	pci_addr_t map, testval;
 	int mapsize;
 
@@ -5089,8 +5090,17 @@ pci_reserve_map(device_t dev, device_t c
 		device_printf(child,
 		    "Lazy allocation of %#jx bytes rid %#x type %d at %#jx\n",
 		    count, *rid, type, rman_get_start(res));
+
+	/* Disable decoding via the CMD register before updating the BAR */
+	cmd = pci_read_config(child, PCIR_COMMAND, 2);
+	pci_write_config(child, PCIR_COMMAND,
+	    cmd & ~(PCI_BAR_MEM(map) ? PCIM_CMD_MEMEN : PCIM_CMD_PORTEN), 2);
+
 	map = rman_get_start(res);
 	pci_write_bar(child, pm, map);
+
+	/* Restore the original value of the CMD register */
+	pci_write_config(child, PCIR_COMMAND, cmd, 2);
 out:
 	return (res);
 }