samsung: pm-check: Make checksum algorithm more configurable and add sum

There are good reasons for using different checksums in pm-check.  Add
'sum' and generalize mechanism for switching checksum algorithms.

The 'sum' algorithm is now the default.

BUG=chrome-os-partner:15655
TEST=Put code in to do a bogus corruption of address
0x71735644 to 0xBADC0DE1.  Then:
1. Do a suspend/resume and see sum algorithm (0xffffffff + 0xbadc0de1):
    s3c_pm_check: Restore CRC error at 71734000 (badc0de0 vs ffffffff)
    bitfix_recover_chunk: Attempting recovery at 71734000
    ...fixed 0x71735644 from 0xbadc0de1 to 0x00000000
2. Switch to xor:
    echo -n xor > /sys/module/pm_check/parameters/pm_check_checksum_type
3. Do suspend/resume again and see xor algorithm (0xffffffff ^ 0xbadc0de1)
    s3c_pm_check: Restore CRC error at 71734000 (4523f21e vs ffffffff)
    bitfix_recover_chunk: Attempting recovery at 71734000
    ...fixed 0x71735644 from 0xbadc0de1 to 0x00000000
4. Switch to CRC:
    echo -n crc > /sys/module/pm_check/parameters/pm_check_checksum_type
5. Do suspend/resume again and see crc algorithm
    s3c_pm_check: Restore CRC error at 71734000 (57243536 vs 270b666b)
    bitfix_recover_chunk: Attempting recovery at 71734000
    ...fixed 0x71735644 from 0xbadc0de1 to 0x00000000
TEST=Time by doing this for sum:
    echo Y > /sys/module/pm_check/parameters/pm_check_print_timings
    suspend_stress_test --noerrors_fatal --backup_rtc \
        --suspend_min 15 --suspend_max 15 -c2
    dmesg | grep 'memory scan'
...and saw this, which is same as xor:
    s3c_pm_check: Suspend memory scan took 4519985 usecs
    s3c_pm_check: Resume memory scan took 1181126 usecs
    s3c_pm_check: Suspend memory scan took 4596896 usecs
    s3c_pm_check: Resume memory scan took 1184638 usecs
...note that the above includes bitfix, which is why suspend is 4.5
seconds.

Change-Id: Ifd20c5d3f6da5069634360057120b63e232f8a77
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/37592
Reviewed-by: Jon Kliegman <kliegs@chromium.org>

diff --git a/arch/arm/plat-samsung/pm-check.c b/arch/arm/plat-samsung/pm-check.c
index c82aa0b..3155fa3 100644 (file)
--- a/arch/arm/plat-samsung/pm-check.c
+++ b/arch/arm/plat-samsung/pm-check.c
@@ -43,7 +43,19 @@
  * and reducing the size will cause the CRC save area to grow
 */
 
-static bool pm_check_use_xor = 1;
+/*
+ * Possible values for pm_check_checksum_type:
+ * - crc: Best (but slowest).  Catches the most problems.
+ * - sum: Simple 32-bit sum.
+ * - xor: Simple 32-bit xor.  Bad at catching problems but gives you more
+ *        information about the problems you caught (you can tell if all
+ *        errors were in the same byte, etc).
+ */
+#define CHECKSUM_TYPE_CRC      "crc"
+#define CHECKSUM_TYPE_SUM      "sum"
+#define CHECKSUM_TYPE_XOR      "xor"
+
+static char *pm_check_checksum_type = CHECKSUM_TYPE_SUM;
 static bool pm_check_enabled;
 static bool pm_check_should_panic = 1;
 static bool pm_check_print_skips;
@@ -53,14 +65,16 @@ static int pm_check_chunksize = CONFIG_SAMSUNG_PM_CHECK_CHUNKSIZE * 1024;
 static u32 crc_size;   /* size needed for the crc block */
 static u32 *crcs;      /* allocated over suspend/resume */
 
+static u32 (*checksum_func)(u32 val, unsigned char const *ptr, size_t len);
+
 /* number of errors found this resume */
 static __suspend_volatile_bss u32 crc_err_cnt;
 
 
 typedef u32 *(run_fn_t)(struct resource *ptr, u32 *arg);
 
-module_param(pm_check_use_xor, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(pm_check_use_xor, "Use XOR checks instead of CRC");
+module_param(pm_check_checksum_type, charp, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(pm_check_checksum_type, "Checksum type (crc, xor, or sum)");
 module_param(pm_check_enabled, bool, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(pm_check_enabled,
                "Enable memory validation on suspend/resume");
@@ -82,13 +96,33 @@ MODULE_PARM_DESC(pm_check_chunksize,
  * @len: Length (in bytes) of the memory range
  *
  */
-static u32 s3c_pm_xor_mem(u32 val, const u32 *ptr, size_t len)
+
+static u32 s3c_pm_xor_mem(u32 val, unsigned char const *ptr, size_t len)
+{
+       const u32 *word_ptr = (const u32 *)ptr;
+       int i;
+
+       len >>= 2; /* get words, not bytes */
+       for (i = 0; i < len; i++, word_ptr++)
+               val ^= *word_ptr;
+       return val;
+}
+
+/**
+ * s3c_pm_sum_mem() - Sum all the words in the memory range passed
+ * @val: Initial value to start the sum from
+ * @ptr: Pointer to the start of the memory range
+ * @len: Length (in bytes) of the memory range
+ *
+ */
+static u32 s3c_pm_sum_mem(u32 val, unsigned char const *ptr, size_t len)
 {
+       const u32 *word_ptr = (const u32 *)ptr;
        int i;
 
        len >>= 2; /* get words, not bytes */
-       for (i = 0; i < len; i++, ptr++)
-               val ^= *ptr;
+       for (i = 0; i < len; i++, word_ptr++)
+               val += *word_ptr;
        return val;
 }
 
@@ -127,10 +161,7 @@ static inline u32 s3c_pm_process_mem(u32 val, u32 addr, size_t len,
                                pfn, addr + len - processed);
                        return val;
                }
-               if (pm_check_use_xor)
-                       val = s3c_pm_xor_mem(val, virt, left);
-               else
-                       val = crc32_le(val, virt, left);
+               val = checksum_func(val, virt, left);
                kunmap_atomic(virt);
 
                if (for_save)
@@ -197,6 +228,17 @@ void s3c_pm_check_prepare(void)
        if (!pm_check_enabled)
                return;
 
+       if (strcasecmp(pm_check_checksum_type, CHECKSUM_TYPE_CRC) == 0) {
+               checksum_func = crc32_le;
+       } else if (strcasecmp(pm_check_checksum_type, CHECKSUM_TYPE_XOR) == 0) {
+               checksum_func = s3c_pm_xor_mem;
+       } else {
+               if (strcasecmp(pm_check_checksum_type, CHECKSUM_TYPE_SUM) != 0)
+                       pr_warn("pm_check: Unknown checksum '%s'; using '%s'\n",
+                               pm_check_checksum_type, CHECKSUM_TYPE_SUM);
+               checksum_func = s3c_pm_sum_mem;
+       }
+
        crc_size = 0;
        /* Timing code generates warnings at this point in suspend */
        if (pm_check_print_timings)