ARC: PAE40: don't panic and instead turn off hw ioc

HSDK currently panics when built for HIGHMEM/ARC_HAS_PAE40 because ioc
is enabled with default which doesn't work for the 2 non contiguous
memory nodes. So get PAE working by disabling ioc instead.

Tested with !PAE40 by forcing @ioc_enable=0 and running the glibc
testsuite over ssh

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index 4135abe..63e6e65 100644 (file)
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -113,10 +113,24 @@ static void read_decode_cache_bcr_arcv2(int cpu)
        }
 
        READ_BCR(ARC_REG_CLUSTER_BCR, cbcr);
-       if (cbcr.c)
+       if (cbcr.c) {
                ioc_exists = 1;
-       else
+
+               /*
+                * As for today we don't support both IOC and ZONE_HIGHMEM enabled
+                * simultaneously. This happens because as of today IOC aperture covers
+                * only ZONE_NORMAL (low mem) and any dma transactions outside this
+                * region won't be HW coherent.
+                * If we want to use both IOC and ZONE_HIGHMEM we can use
+                * bounce_buffer to handle dma transactions to HIGHMEM.
+                * Also it is possible to modify dma_direct cache ops or increase IOC
+                * aperture size if we are planning to use HIGHMEM without PAE.
+                */
+               if (IS_ENABLED(CONFIG_HIGHMEM) || is_pae40_enabled())
+                       ioc_enable = 0;
+       } else {
                ioc_enable = 0;
+       }
 
        /* HS 2.0 didn't have AUX_VOL */
        if (cpuinfo_arc700[cpu].core.family > 0x51) {
@@ -1158,19 +1172,6 @@ noinline void __init arc_ioc_setup(void)
        if (!ioc_enable)
                return;
 
-       /*
-        * As for today we don't support both IOC and ZONE_HIGHMEM enabled
-        * simultaneously. This happens because as of today IOC aperture covers
-        * only ZONE_NORMAL (low mem) and any dma transactions outside this
-        * region won't be HW coherent.
-        * If we want to use both IOC and ZONE_HIGHMEM we can use
-        * bounce_buffer to handle dma transactions to HIGHMEM.
-        * Also it is possible to modify dma_direct cache ops or increase IOC
-        * aperture size if we are planning to use HIGHMEM without PAE.
-        */
-       if (IS_ENABLED(CONFIG_HIGHMEM))
-               panic("IOC and HIGHMEM can't be used simultaneously");
-
        /* Flush + invalidate + disable L1 dcache */
        __dc_disable();