Author: cem
Date: Tue Oct 13 23:43:06 2015
New Revision: 289274
URL: https://svnweb.freebsd.org/changeset/base/289274
Log:
NTB: MFV 58b88920: Document HW errata
Add a comment describing the necessary ordering of modifications to the
NTB Limit and Base registers.
Authored by: Jon Mason
Obtained from: Linux (Dual BSD/GPL driver)
Sponsored by: EMC / Isilon Storage Division
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 Tue Oct 13 23:42:13 2015
(r289273)
+++ head/sys/dev/ntb/ntb_hw/ntb_hw.c Tue Oct 13 23:43:06 2015
(r289274)
@@ -764,6 +764,11 @@ ntb_setup_xeon(struct ntb_softc *ntb)
* which may hang the system. To workaround this use the second memory
* window to access the interrupt and scratch pad registers on the
* remote system.
+ *
+ * There is another HW errata on the limit registers -- they can only
+ * be written when the base register is (?)4GB aligned and < 32-bit.
+ * This should already be the case based on the driver defaults, but
+ * write the limit registers first just in case.
*/
if (HAS_FEATURE(NTB_REGS_THRU_MW))
/*
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