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From: Adrian Chadd <adrian@FreeBSD.org>
Date: Sun, 28 May 2017 07:44:55 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r319055 - head/sys/mips/atheros
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Author: adrian
Date: Sun May 28 07:44:55 2017
New Revision: 319055
URL: https://svnweb.freebsd.org/changeset/base/319055

Log:
  [ar71xx] undo read-after-write to flush; some bus devices dislike this.
  
  This broke the PCI fixup on at least the AR7240 + AR9280 reference design
  board that I have.
  
  Tested:
  
  * Atheros AP93 reference design - AR7240 + AR9280

Modified:
  head/sys/mips/atheros/ar71xxreg.h

Modified: head/sys/mips/atheros/ar71xxreg.h
==============================================================================
--- head/sys/mips/atheros/ar71xxreg.h	Sun May 28 07:40:42 2017	(r319054)
+++ head/sys/mips/atheros/ar71xxreg.h	Sun May 28 07:44:55 2017	(r319055)
@@ -528,13 +528,14 @@ typedef enum {
 #define		AR71XX_SPI_RDS		0x0C
 
 #define ATH_READ_REG(reg) \
-    *((volatile uint32_t *)MIPS_PHYS_TO_KSEG1((reg)))
-
+	*((volatile uint32_t *)MIPS_PHYS_TO_KSEG1((reg)))
+/*
+ * Note: Don't put a flush read here; some users (eg the AR724x PCI fixup code)
+ * requires write-only space to certain registers.  Doing the read afterwards
+ * causes things to break.
+ */
 #define ATH_WRITE_REG(reg, val) \
-    do { \
-      *((volatile uint32_t *)MIPS_PHYS_TO_KSEG1((reg))) = (val); \
-      (void) ATH_READ_REG(reg); \
-    } while (0)
+      *((volatile uint32_t *)MIPS_PHYS_TO_KSEG1((reg))) = (val)
 
 static inline void
 ar71xx_ddr_flush(uint32_t reg)