svn commit: r302531 - head/sys/dev/ntb/ntb_hw

[Alexander Motin]

Author: mav
Date: Sun Jul 10 20:22:04 2016
New Revision: 302531
URL: https://svnweb.freebsd.org/changeset/base/302531

Log:
  Revert odd change, setting limit registers before base.
  
  I don't know what errata is mentioned there, I was unable to find it, but
  setting limit before the base simply does not work at all.  According to
  specification attempt to set limit out of the present window range resets
  it to zero, effectively disabling it.  And that is what I see in practice.
  
  Fixing this properly disables access for remote side to our memory until
  respective xlat is negotiated and set.  As I see, Linux does the same.

Modified:
  head/sys/dev/ntb/ntb_hw/ntb_hw.c

Modified: head/sys/dev/ntb/ntb_hw/ntb_hw.c
==============================================================================
--- head/sys/dev/ntb/ntb_hw/ntb_hw.c	Sun Jul 10 19:52:26 2016	(r302530)
+++ head/sys/dev/ntb/ntb_hw/ntb_hw.c	Sun Jul 10 20:22:04 2016	(r302531)
@@ -1699,26 +1699,22 @@ xeon_set_sbar_base_and_limit(struct ntb_
 			bar_addr = 0;
 	}
 
-	/*
-	 * Set limit registers first to avoid an errata where setting the base
-	 * registers locks the limit registers.
-	 */
 	if (!bar_is_64bit(ntb, idx)) {
-		ntb_reg_write(4, lmt_reg, bar_addr);
-		reg_val = ntb_reg_read(4, lmt_reg);
-		(void)reg_val;
-
 		ntb_reg_write(4, base_reg, bar_addr);
 		reg_val = ntb_reg_read(4, base_reg);
 		(void)reg_val;
-	} else {
-		ntb_reg_write(8, lmt_reg, bar_addr);
-		reg_val = ntb_reg_read(8, lmt_reg);
-		(void)reg_val;
 
+		ntb_reg_write(4, lmt_reg, bar_addr);
+		reg_val = ntb_reg_read(4, lmt_reg);
+		(void)reg_val;
+	} else {
 		ntb_reg_write(8, base_reg, bar_addr);
 		reg_val = ntb_reg_read(8, base_reg);
 		(void)reg_val;
+
+		ntb_reg_write(8, lmt_reg, bar_addr);
+		reg_val = ntb_reg_read(8, lmt_reg);
+		(void)reg_val;
 	}
 }