arch/tile/lib/cacheflush.c

   1 /*
   2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  */
  14
  15 #include <linux/export.h>
  16 #include <asm/page.h>
  17 #include <asm/cacheflush.h>
  18 #include <arch/icache.h>
  19 #include <arch/spr_def.h>
  20
  21
  22 void __flush_icache_range(unsigned long start, unsigned long end)
  23 {
  24         invalidate_icache((const void *)start, end - start, PAGE_SIZE);
  25 }
  26
  27
  28 /* Force a load instruction to issue. */
  29 static inline void force_load(char *p)
  30 {
  31         *(volatile char *)p;
  32 }
  33
  34 /*
  35  * Flush and invalidate a VA range that is homed remotely on a single
  36  * core (if "!hfh") or homed via hash-for-home (if "hfh"), waiting
  37  * until the memory controller holds the flushed values.
  38  */
  39 void __attribute__((optimize("omit-frame-pointer")))
  40 finv_buffer_remote(void *buffer, size_t size, int hfh)
  41 {
  42         char *p, *base;
  43         size_t step_size, load_count;
  44
  45         /*
  46          * On TILEPro the striping granularity is a fixed 8KB; on
  47          * TILE-Gx it is configurable, and we rely on the fact that
  48          * the hypervisor always configures maximum striping, so that
  49          * bits 9 and 10 of the PA are part of the stripe function, so
  50          * every 512 bytes we hit a striping boundary.
  51          *
  52          */
  53 #ifdef __tilegx__
  54         const unsigned long STRIPE_WIDTH = 512;
  55 #else
  56         const unsigned long STRIPE_WIDTH = 8192;
  57 #endif
  58
  59 #ifdef __tilegx__
  60         /*
  61          * On TILE-Gx, we must disable the dstream prefetcher before doing
  62          * a cache flush; otherwise, we could end up with data in the cache
  63          * that we don't want there.  Note that normally we'd do an mf
  64          * after the SPR write to disabling the prefetcher, but we do one
  65          * below, before any further loads, so there's no need to do it
  66          * here.
  67          */
  68         uint_reg_t old_dstream_pf = __insn_mfspr(SPR_DSTREAM_PF);
  69         __insn_mtspr(SPR_DSTREAM_PF, 0);
  70 #endif
  71
  72         /*
  73          * Flush and invalidate the buffer out of the local L1/L2
  74          * and request the home cache to flush and invalidate as well.
  75          */
  76         __finv_buffer(buffer, size);
  77
  78         /*
  79          * Wait for the home cache to acknowledge that it has processed
  80          * all the flush-and-invalidate requests.  This does not mean
  81          * that the flushed data has reached the memory controller yet,
  82          * but it does mean the home cache is processing the flushes.
  83          */
  84         __insn_mf();
  85
  86         /*
  87          * Issue a load to the last cache line, which can't complete
  88          * until all the previously-issued flushes to the same memory
  89          * controller have also completed.  If we weren't striping
  90          * memory, that one load would be sufficient, but since we may
  91          * be, we also need to back up to the last load issued to
  92          * another memory controller, which would be the point where
  93          * we crossed a "striping" boundary (the granularity of striping
  94          * across memory controllers).  Keep backing up and doing this
  95          * until we are before the beginning of the buffer, or have
  96          * hit all the controllers.
  97          *
  98          * If we are flushing a hash-for-home buffer, it's even worse.
  99          * Each line may be homed on a different tile, and each tile
 100          * may have up to four lines that are on different
 101          * controllers.  So as we walk backwards, we have to touch
 102          * enough cache lines to satisfy these constraints.  In
 103          * practice this ends up being close enough to "load from
 104          * every cache line on a full memory stripe on each
 105          * controller" that we simply do that, to simplify the logic.
 106          *
 107          * On TILE-Gx the hash-for-home function is much more complex,
 108          * with the upshot being we can't readily guarantee we have
 109          * hit both entries in the 128-entry AMT that were hit by any
 110          * load in the entire range, so we just re-load them all.
 111          * With larger buffers, we may want to consider using a hypervisor
 112          * trap to issue loads directly to each hash-for-home tile for
 113          * each controller (doing it from Linux would trash the TLB).
 114          */
 115         if (hfh) {
 116                 step_size = L2_CACHE_BYTES;
 117 #ifdef __tilegx__
 118                 load_count = (size + L2_CACHE_BYTES - 1) / L2_CACHE_BYTES;
 119 #else
 120                 load_count = (STRIPE_WIDTH / L2_CACHE_BYTES) *
 121                               (1 << CHIP_LOG_NUM_MSHIMS());
 122 #endif
 123         } else {
 124                 step_size = STRIPE_WIDTH;
 125                 load_count = (1 << CHIP_LOG_NUM_MSHIMS());
 126         }
 127
 128         /* Load the last byte of the buffer. */
 129         p = (char *)buffer + size - 1;
 130         force_load(p);
 131
 132         /* Bump down to the end of the previous stripe or cache line. */
 133         p -= step_size;
 134         p = (char *)((unsigned long)p | (step_size - 1));
 135
 136         /* Figure out how far back we need to go. */
 137         base = p - (step_size * (load_count - 2));
 138         if ((unsigned long)base < (unsigned long)buffer)
 139                 base = buffer;
 140
 141         /*
 142          * Fire all the loads we need.  The MAF only has eight entries
 143          * so we can have at most eight outstanding loads, so we
 144          * unroll by that amount.
 145          */
 146 #pragma unroll 8
 147         for (; p >= base; p -= step_size)
 148                 force_load(p);
 149
 150         /*
 151          * Repeat, but with finv's instead of loads, to get rid of the
 152          * data we just loaded into our own cache and the old home L3.
 153          * No need to unroll since finv's don't target a register.
 154          * The finv's are guaranteed not to actually flush the data in
 155          * the buffer back to their home, since we just read it, so the
 156          * lines are clean in cache; we will only invalidate those lines.
 157          */
 158         p = (char *)buffer + size - 1;
 159         __insn_finv(p);
 160         p -= step_size;
 161         p = (char *)((unsigned long)p | (step_size - 1));
 162         for (; p >= base; p -= step_size)
 163                 __insn_finv(p);
 164
 165         /* Wait for these finv's (and thus the first finvs) to be done. */
 166         __insn_mf();
 167
 168 #ifdef __tilegx__
 169         /* Reenable the prefetcher. */
 170         __insn_mtspr(SPR_DSTREAM_PF, old_dstream_pf);
 171 #endif
 172 }
 173 EXPORT_SYMBOL_GPL(finv_buffer_remote);