ARCv2: PAE40: set MSB even if !CONFIG_ARC_HAS_PAE40 but PAE exists in SoC

PAE40 confiuration in hardware extends some of the address registers
for TLB/cache ops to 2 words.

So far kernel was NOT setting the higher word if feature was not enabled
in software which is wrong. Those need to be set to 0 in such case.

Normally this would be done in the cache flush / tlb ops, however since
these registers only exist conditionally, this would have to be
conditional to a flag being set on boot which is expensive/ugly -
specially for the more common case of PAE exists but not in use.
Optimize that by zero'ing them once at boot - nobody will write to
them afterwards

Cc: stable@vger.kernel.org   #4.4+
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --git a/arch/arc/include/asm/mmu.h b/arch/arc/include/asm/mmu.h
index db7319e..efb79fa 100644 (file)
--- a/arch/arc/include/asm/mmu.h
+++ b/arch/arc/include/asm/mmu.h
@@ -94,6 +94,8 @@ static inline int is_pae40_enabled(void)
        return IS_ENABLED(CONFIG_ARC_HAS_PAE40);
 }
 
+extern int pae40_exist_but_not_enab(void);
+
 #endif /* !__ASSEMBLY__ */
 
 #endif

diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index 874913b..7db283b 100644 (file)
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -1123,6 +1123,13 @@ noinline void __init arc_ioc_setup(void)
        __dc_enable();
 }
 
+/*
+ * Cache related boot time checks/setups only needed on master CPU:
+ *  - Geometry checks (kernel build and hardware agree: e.g. L1_CACHE_BYTES)
+ *    Assume SMP only, so all cores will have same cache config. A check on
+ *    one core suffices for all
+ *  - IOC setup / dma callbacks only need to be done once
+ */
 void __init arc_cache_init_master(void)
 {
        unsigned int __maybe_unused cpu = smp_processor_id();
@@ -1202,12 +1209,27 @@ void __ref arc_cache_init(void)
 
        printk(arc_cache_mumbojumbo(0, str, sizeof(str)));
 
-       /*
-        * Only master CPU needs to execute rest of function:
-        *  - Assume SMP so all cores will have same cache config so
-        *    any geomtry checks will be same for all
-        *  - IOC setup / dma callbacks only need to be setup once
-        */
        if (!cpu)
                arc_cache_init_master();
+
+       /*
+        * In PAE regime, TLB and cache maintenance ops take wider addresses
+        * And even if PAE is not enabled in kernel, the upper 32-bits still need
+        * to be zeroed to keep the ops sane.
+        * As an optimization for more common !PAE enabled case, zero them out
+        * once at init, rather than checking/setting to 0 for every runtime op
+        */
+       if (is_isa_arcv2() && pae40_exist_but_not_enab()) {
+
+               if (IS_ENABLED(CONFIG_ARC_HAS_ICACHE))
+                       write_aux_reg(ARC_REG_IC_PTAG_HI, 0);
+
+               if (IS_ENABLED(CONFIG_ARC_HAS_DCACHE))
+                       write_aux_reg(ARC_REG_DC_PTAG_HI, 0);
+
+               if (l2_line_sz) {
+                       write_aux_reg(ARC_REG_SLC_RGN_END1, 0);
+                       write_aux_reg(ARC_REG_SLC_RGN_START1, 0);
+               }
+       }
 }

diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c
index d0126fd..b181f3e 100644 (file)
--- a/arch/arc/mm/tlb.c
+++ b/arch/arc/mm/tlb.c
@@ -104,6 +104,8 @@
 /* A copy of the ASID from the PID reg is kept in asid_cache */
 DEFINE_PER_CPU(unsigned int, asid_cache) = MM_CTXT_FIRST_CYCLE;
 
+static int __read_mostly pae_exists;
+
 /*
  * Utility Routine to erase a J-TLB entry
  * Caller needs to setup Index Reg (manually or via getIndex)
@@ -784,7 +786,7 @@ void read_decode_mmu_bcr(void)
                mmu->u_dtlb = mmu4->u_dtlb * 4;
                mmu->u_itlb = mmu4->u_itlb * 4;
                mmu->sasid = mmu4->sasid;
-               mmu->pae = mmu4->pae;
+               pae_exists = mmu->pae = mmu4->pae;
        }
 }
 
@@ -809,6 +811,11 @@ char *arc_mmu_mumbojumbo(int cpu_id, char *buf, int len)
        return buf;
 }
 
+int pae40_exist_but_not_enab(void)
+{
+       return pae_exists && !is_pae40_enabled();
+}
+
 void arc_mmu_init(void)
 {
        char str[256];
@@ -859,6 +866,9 @@ void arc_mmu_init(void)
        /* swapper_pg_dir is the pgd for the kernel, used by vmalloc */
        write_aux_reg(ARC_REG_SCRATCH_DATA0, swapper_pg_dir);
 #endif
+
+       if (pae40_exist_but_not_enab())
+               write_aux_reg(ARC_REG_TLBPD1HI, 0);
 }
 
 /*