MIPS: RM7000: Add support for tertiary cache

Add support for the external T-cache interface. Allow for platform
independent size probing from 512KB to 8MB in powers of two.

Signed-off-by: Ricardo Mendoza <ricmm@gentoo.org>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1477/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 130 insertions, 23 deletions

diff --git a/arch/mips/include/asm/cacheops.h b/arch/mips/include/asm/cacheops.h
index 256ad2cc6eb8..8f99c11ab665 100644
--- a/arch/mips/include/asm/cacheops.h
+++ b/arch/mips/include/asm/cacheops.h
@@ -62,6 +62,8 @@
  * RM7000-specific cacheops
  */
 #define Page_Invalidate_T       0x16
+#define Index_Store_Tag_T       0x0a
+#define Index_Load_Tag_T        0x06
 
 /*
  * R10000-specific cacheops
diff --git a/arch/mips/mm/sc-rm7k.c b/arch/mips/mm/sc-rm7k.c
index 53634398a56d..1ef75cd80a0d 100644
--- a/arch/mips/mm/sc-rm7k.c
+++ b/arch/mips/mm/sc-rm7k.c
@@ -16,6 +16,7 @@
 #include <asm/cacheops.h>
 #include <asm/mipsregs.h>
 #include <asm/processor.h>
+#include <asm/sections.h>
 #include <asm/cacheflush.h> /* for run_uncached() */
 
 /* Primary cache parameters. */
@@ -25,11 +26,15 @@
 /* Secondary cache parameters. */
 #define scache_size     (256*1024)      /* Fixed to 256KiB on RM7000 */
 
+/* Tertiary cache parameters */
+#define tc_lsize        32
+
 extern unsigned long icache_way_size, dcache_way_size;
+unsigned long tcache_size;
 
 #include <asm/r4kcache.h>
 
-static int rm7k_tcache_enabled;
+static int rm7k_tcache_init;
 
 /*
  * Writeback and invalidate the primary cache dcache before DMA.
@@ -46,7 +51,7 @@ static void rm7k_sc_wback_inv(unsigned long addr, unsigned long size)
 
         blast_scache_range(addr, addr + size);
 
-        if (!rm7k_tcache_enabled)
+        if (!rm7k_tcache_init)
                 return;
 
         a = addr & ~(tc_pagesize - 1);
@@ -70,7 +75,7 @@ static void rm7k_sc_inv(unsigned long addr, unsigned long size)
 
         blast_inv_scache_range(addr, addr + size);
 
-        if (!rm7k_tcache_enabled)
+        if (!rm7k_tcache_init)
                 return;
 
         a = addr & ~(tc_pagesize - 1);
@@ -83,6 +88,45 @@ static void rm7k_sc_inv(unsigned long addr, unsigned long size)
         }
 }
 
+static void blast_rm7k_tcache(void)
+{
+        unsigned long start = CKSEG0ADDR(0);
+        unsigned long end = start + tcache_size;
+
+        write_c0_taglo(0);
+
+        while (start < end) {
+                cache_op(Page_Invalidate_T, start);
+                start += tc_pagesize;
+        }
+}
+
+/*
+ * This function is executed in uncached address space.
+ */
+static __cpuinit void __rm7k_tc_enable(void)
+{
+        int i;
+
+        set_c0_config(RM7K_CONF_TE);
+
+        write_c0_taglo(0);
+        write_c0_taghi(0);
+
+        for (i = 0; i < tcache_size; i += tc_lsize)
+                cache_op(Index_Store_Tag_T, CKSEG0ADDR(i));
+}
+
+static __cpuinit void rm7k_tc_enable(void)
+{
+        if (read_c0_config() & RM7K_CONF_TE)
+                return;
+
+        BUG_ON(tcache_size == 0);
+
+        run_uncached(__rm7k_tc_enable);
+}
+
 /*
  * This function is executed in uncached address space.
  */
@@ -104,13 +148,29 @@ static __cpuinit void rm7k_sc_enable(void)
         if (read_c0_config() & RM7K_CONF_SE)
                 return;
 
-        printk(KERN_INFO "Enabling secondary cache...\n");
+        pr_info("Enabling secondary cache...\n");
         run_uncached(__rm7k_sc_enable);
+
+        if (rm7k_tcache_init)
+                rm7k_tc_enable();
+}
+
+static void rm7k_tc_disable(void)
+{
+        unsigned long flags;
+
+        local_irq_save(flags);
+        blast_rm7k_tcache();
+        clear_c0_config(RM7K_CONF_TE);
+        local_irq_save(flags);
 }
 
 static void rm7k_sc_disable(void)
 {
         clear_c0_config(RM7K_CONF_SE);
+
+        if (rm7k_tcache_init)
+                rm7k_tc_disable();
 }
 
 static struct bcache_ops rm7k_sc_ops = {
@@ -120,6 +180,52 @@ static struct bcache_ops rm7k_sc_ops = {
         .bc_inv = rm7k_sc_inv
 };
 
+/*
+ * This is a probing function like the one found in c-r4k.c, we look for the
+ * wrap around point with different addresses.
+ */
+static __cpuinit void __probe_tcache(void)
+{
+        unsigned long flags, addr, begin, end, pow2;
+
+        begin = (unsigned long) &_stext;
+        begin  &= ~((8 * 1024 * 1024) - 1);
+        end = begin + (8 * 1024 * 1024);
+
+        local_irq_save(flags);
+
+        set_c0_config(RM7K_CONF_TE);
+
+        /* Fill size-multiple lines with a valid tag */
+        pow2 = (256 * 1024);
+        for (addr = begin; addr <= end; addr = (begin + pow2)) {
+                unsigned long *p = (unsigned long *) addr;
+                __asm__ __volatile__("nop" : : "r" (*p));
+                pow2 <<= 1;
+        }
+
+        /* Load first line with a 0 tag, to check after */
+        write_c0_taglo(0);
+        write_c0_taghi(0);
+        cache_op(Index_Store_Tag_T, begin);
+
+        /* Look for the wrap-around */
+        pow2 = (512 * 1024);
+        for (addr = begin + (512 * 1024); addr <= end; addr = begin + pow2) {
+                cache_op(Index_Load_Tag_T, addr);
+                if (!read_c0_taglo())
+                        break;
+                pow2 <<= 1;
+        }
+
+        addr -= begin;
+        tcache_size = addr;
+
+        clear_c0_config(RM7K_CONF_TE);
+
+        local_irq_restore(flags);
+}
+
 void __cpuinit rm7k_sc_init(void)
 {
         struct cpuinfo_mips *c = &current_cpu_data;
@@ -139,27 +245,26 @@ void __cpuinit rm7k_sc_init(void)
         if (!(config & RM7K_CONF_SE))
                 rm7k_sc_enable();
 
+        bcops = &rm7k_sc_ops;
+
         /*
          * While we're at it let's deal with the tertiary cache.
          */
-        if (!(config & RM7K_CONF_TC)) {
-
-                /*
-                 * We can't enable the L3 cache yet. There may be board-specific
-                 * magic necessary to turn it on, and blindly asking the CPU to
-                 * start using it would may give cache errors.
-                 *
-                 * Also, board-specific knowledge may allow us to use the
-                 * CACHE Flash_Invalidate_T instruction if the tag RAM supports
-                 * it, and may specify the size of the L3 cache so we don't have
-                 * to probe it.
-                 */
-                printk(KERN_INFO "Tertiary cache present, %s enabled\n",
-                       (config & RM7K_CONF_TE) ? "already" : "not (yet)");
-
-                if ((config & RM7K_CONF_TE))
-                        rm7k_tcache_enabled = 1;
-        }
 
-        bcops = &rm7k_sc_ops;
+        rm7k_tcache_init = 0;
+        tcache_size = 0;
+
+        if (config & RM7K_CONF_TC)
+                return;
+
+        /*
+         * No efficient way to ask the hardware for the size of the tcache,
+         * so must probe for it.
+         */
+        run_uncached(__probe_tcache);
+        rm7k_tc_enable();
+        rm7k_tcache_init = 1;
+        c->tcache.linesz = tc_lsize;
+        c->tcache.ways = 1;
+        pr_info("Tertiary cache size %ldK.\n", (tcache_size >> 10));
 }