Blackfin arch: Use DTEST rather than DMA to poke at L1 SRAM during exception context

Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

2 files changed, 202 insertions, 1 deletions

diff --git a/arch/blackfin/mm/Makefile b/arch/blackfin/mm/Makefile
index 81aacbc32d3c..d489f894f4b1 100644
--- a/arch/blackfin/mm/Makefile
+++ b/arch/blackfin/mm/Makefile
@@ -2,4 +2,4 @@
 # arch/blackfin/mm/Makefile
 #
 
-obj-y := sram-alloc.o init.o
+obj-y := sram-alloc.o isram-driver.o init.o
diff --git a/arch/blackfin/mm/isram-driver.c b/arch/blackfin/mm/isram-driver.c
new file mode 100644
index 000000000000..22913e7a1818
--- /dev/null
+++ b/arch/blackfin/mm/isram-driver.c
@@ -0,0 +1,201 @@
+/*
+ * Description: Instruction SRAM accessor functions for the Blackfin
+ *
+ * Copyright 2008 Analog Devices Inc.
+ *
+ * Bugs: Enter bugs at http://blackfin.uclinux.org/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see the file COPYING, or write
+ * to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+
+#include <asm/blackfin.h>
+
+/*
+ * IMPORTANT WARNING ABOUT THESE FUNCTIONS
+ *
+ * The emulator will not function correctly if a write command is left in
+ * ITEST_COMMAND or DTEST_COMMAND AND access to cache memory is needed by
+ * the emulator. To avoid such problems, ensure that both ITEST_COMMAND
+ * and DTEST_COMMAND are zero when exiting these functions.
+ */
+
+
+/*
+ * On the Blackfin, L1 instruction sram (which operates at core speeds) can not
+ * be accessed by a normal core load, so we need to go through a few hoops to
+ * read/write it.
+ * To try to make it easier - we export a memcpy interface, where either src or
+ * dest can be in this special L1 memory area.
+ * The low level read/write functions should not be exposed to the rest of the
+ * kernel, since they operate on 64-bit data, and need specific address alignment
+ */
+
+static DEFINE_SPINLOCK(dtest_lock);
+
+/* Takes a void pointer */
+#define IADDR2DTEST(x) \
+        ({ unsigned long __addr = (unsigned long)(x); \
+                (__addr & 0x47F8)        | /* address bits 14 & 10:3 */ \
+                (__addr & 0x0800) << 15  | /* address bit  11        */ \
+                (__addr  & 0x3000) << 4  | /* address bits 13:12     */ \
+                (__addr  & 0x8000) << 8  | /* address bit  15        */ \
+                (0x1000004);               /* isram access           */ \
+        })
+
+/* Takes a pointer, and returns the offset (in bits) which things should be shifted */
+#define ADDR2OFFSET(x) ((((unsigned long)(x)) & 0x7) * 8)
+
+/* Takes a pointer, determines if it is the last byte in the isram 64-bit data type */
+#define ADDR2LAST(x) ((((unsigned long)x) & 0x7) == 0x7)
+
+static void isram_write(const void *addr, uint64_t data)
+{
+        uint32_t cmd;
+        unsigned long flags;
+
+        if (addr >= (void *)(L1_CODE_START + L1_CODE_LENGTH))
+                return;
+
+        cmd = IADDR2DTEST(addr) | 1;             /* write */
+
+        /*
+         * Writes to DTEST_DATA[0:1] need to be atomic with write to DTEST_COMMAND
+         * While in exception context - atomicity is guaranteed or double fault
+         */
+        spin_lock_irqsave(&dtest_lock, flags);
+
+        bfin_write_DTEST_DATA0(data & 0xFFFFFFFF);
+        bfin_write_DTEST_DATA1(data >> 32);
+
+        /* use the builtin, since interrupts are already turned off */
+        __builtin_bfin_csync();
+        bfin_write_DTEST_COMMAND(cmd);
+        __builtin_bfin_csync();
+
+        bfin_write_DTEST_COMMAND(0);
+        __builtin_bfin_csync();
+
+        spin_unlock_irqrestore(&dtest_lock, flags);
+}
+
+static uint64_t isram_read(const void *addr)
+{
+        uint32_t cmd;
+        unsigned long flags;
+        uint64_t ret;
+
+        if (addr > (void *)(L1_CODE_START + L1_CODE_LENGTH))
+                return 0;
+
+        cmd = IADDR2DTEST(addr) | 0;              /* read */
+
+        /*
+         * Reads of DTEST_DATA[0:1] need to be atomic with write to DTEST_COMMAND
+         * While in exception context - atomicity is guaranteed or double fault
+         */
+        spin_lock_irqsave(&dtest_lock, flags);
+        /* use the builtin, since interrupts are already turned off */
+        __builtin_bfin_csync();
+        bfin_write_DTEST_COMMAND(cmd);
+        __builtin_bfin_csync();
+        ret = bfin_read_DTEST_DATA0() | ((uint64_t)bfin_read_DTEST_DATA1() << 32);
+
+        bfin_write_DTEST_COMMAND(0);
+        __builtin_bfin_csync();
+        spin_unlock_irqrestore(&dtest_lock, flags);
+
+        return ret;
+}
+
+static bool isram_check_addr(const void *addr, size_t n)
+{
+        if ((addr >= (void *)L1_CODE_START) &&
+            (addr < (void *)(L1_CODE_START + L1_CODE_LENGTH))) {
+                if ((addr + n) >= (void *)(L1_CODE_START + L1_CODE_LENGTH)) {
+                        show_stack(NULL, NULL);
+                        printk(KERN_ERR "isram_memcpy: copy involving %p length "
+                                        "(%zu) too long\n", addr, n);
+                }
+                return true;
+        }
+        return false;
+}
+
+/*
+ * The isram_memcpy() function copies n bytes from memory area src to memory area dest.
+ * The isram_memcpy() function returns a pointer to dest.
+ * Either dest or src can be in L1 instruction sram.
+ */
+void *isram_memcpy(void *dest, const void *src, size_t n)
+{
+        uint64_t data_in = 0, data_out = 0;
+        size_t count;
+        bool dest_in_l1, src_in_l1, need_data, put_data;
+        unsigned char byte, *src_byte, *dest_byte;
+
+        src_byte = (unsigned char *)src;
+        dest_byte = (unsigned char *)dest;
+
+        dest_in_l1 = isram_check_addr(dest, n);
+        src_in_l1 = isram_check_addr(src, n);
+
+        need_data = true;
+        put_data = true;
+        for (count = 0; count < n; count++) {
+                if (src_in_l1) {
+                        if (need_data) {
+                                data_in = isram_read(src + count);
+                                need_data = false;
+                        }
+
+                        if (ADDR2LAST(src + count))
+                                need_data = true;
+
+                        byte = (unsigned char)((data_in >> ADDR2OFFSET(src + count)) & 0xff);
+
+                } else {
+                        /* src is in L2 or L3 - so just dereference*/
+                        byte = src_byte[count];
+                }
+
+                if (dest_in_l1) {
+                        if (put_data) {
+                                data_out = isram_read(dest + count);
+                                put_data = false;
+                        }
+
+                        data_out &= ~((uint64_t)0xff << ADDR2OFFSET(dest + count));
+                        data_out |= ((uint64_t)byte << ADDR2OFFSET(dest + count));
+
+                        if (ADDR2LAST(dest + count)) {
+                                put_data = true;
+                                isram_write(dest + count, data_out);
+                        }
+                } else {
+                        /* dest in L2 or L3 - so just dereference */
+                        dest_byte[count] = byte;
+                }
+        }
+
+        /* make sure we dump the last byte if necessary */
+        if (dest_in_l1 && !put_data)
+                isram_write(dest + count, data_out);
+
+        return dest;
+}
+EXPORT_SYMBOL(isram_memcpy);
+