svn commit: r362407 - in head/sys/powerpc: booke include

[Brandon Bergren]

Author: bdragon
Date: Fri Jun 19 18:40:39 2020
New Revision: 362407
URL: https://svnweb.freebsd.org/changeset/base/362407

Log:
  [PowerPC] Fix booke64 qemu infinite loop in L2 cache enable
  
  Since qemu does not implement the L2 cache, we get stuck forever waiting
  for a bit to be set when trying to invalidate it.
  
  To prevent that, we should bail out if the L2 cache is missing.
  One easy way to check this is L2CFG0 == 0 (since L2CSIZE always has at
  least one bit set in a valid implementation)
  
  (tested on qemu, rb800, and x5000)
  
  Reviewed by:	jhibbits
  Sponsored by:	Tag1 Consulting, Inc.
  Differential Revision:	https://reviews.freebsd.org/D25225

Modified:
  head/sys/powerpc/booke/machdep_e500.c
  head/sys/powerpc/include/spr.h

Modified: head/sys/powerpc/booke/machdep_e500.c
==============================================================================
--- head/sys/powerpc/booke/machdep_e500.c	Fri Jun 19 18:36:10 2020	(r362406)
+++ head/sys/powerpc/booke/machdep_e500.c	Fri Jun 19 18:40:39 2020	(r362407)
@@ -91,7 +91,17 @@ booke_enable_l2_cache(void)
 	if ((((mfpvr() >> 16) & 0xFFFF) == FSL_E500mc) ||
 	    (((mfpvr() >> 16) & 0xFFFF) == FSL_E5500)) {
 		csr = mfspr(SPR_L2CSR0);
-		if ((csr & L2CSR0_L2E) == 0) {
+		/*
+		 * Don't actually attempt to manipulate the L2 cache if
+		 * L2CFG0 is zero.
+		 *
+		 * Any chip with a working L2 cache will have a nonzero
+		 * L2CFG0, as it will have a nonzero L2CSIZE field.
+		 *
+		 * This fixes waiting forever for cache enable in qemu,
+		 * which does not implement the L2 cache.
+		 */
+		if (mfspr(SPR_L2CFG0) != 0 && (csr & L2CSR0_L2E) == 0) {
 			l2cache_inval();
 			l2cache_enable();
 		}

Modified: head/sys/powerpc/include/spr.h
==============================================================================
--- head/sys/powerpc/include/spr.h	Fri Jun 19 18:36:10 2020	(r362406)
+++ head/sys/powerpc/include/spr.h	Fri Jun 19 18:40:39 2020	(r362407)
@@ -887,6 +887,7 @@
 #define	  L1CSR1_ICFI		0x00000002	/* Instruction Cache Flash Invalidate */
 #define	  L1CSR1_ICE		0x00000001	/* Instruction Cache Enable */
 
+#define	SPR_L2CFG0		0x207	/* ..8 L2 Configuration Register 0 */
 #define	SPR_L2CSR0		0x3F9	/* ..8 L2 Cache Control and Status Register 0 */
 #define	  L2CSR0_L2E		0x80000000	/* L2 Cache Enable */
 #define	  L2CSR0_L2PE		0x40000000	/* L2 Cache Parity Enable */