Input: atmel_mxt_ts - implement CRC check for configuration data

The configuration is stored in NVRAM on the maXTouch chip. When the device
is reset it reports a CRC of the stored configuration values. Therefore it
isn't necessary to send the configuration on each probe - we can check the
CRC matches and avoid a timeconsuming backup/reset cycle.

Signed-off-by: Nick Dyer <nick.dyer@itdev.co.uk>
Acked-by: Benson Leung <bleung@chromium.org>
Acked-by: Yufeng Shen <miletus@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

2 files changed, 53 insertions, 8 deletions

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index 278f364ec6e1..61f9ef221d12 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -188,6 +188,7 @@
 #define MXT_BACKUP_TIME         50      /* msec */
 #define MXT_RESET_TIME          200     /* msec */
 #define MXT_RESET_TIMEOUT       3000    /* msec */
+#define MXT_CRC_TIMEOUT         1000    /* msec */
 #define MXT_FW_RESET_TIME       3000    /* msec */
 #define MXT_FW_CHG_TIMEOUT      300     /* msec */
 
@@ -259,6 +260,7 @@ struct mxt_data {
         unsigned int max_x;
         unsigned int max_y;
         bool in_bootloader;
+        u32 config_crc;
 
         /* Cached parameters from object table */
         u8 T6_reportid;
@@ -272,6 +274,9 @@ struct mxt_data {
 
         /* for reset handling */
         struct completion reset_completion;
+
+        /* for config update handling */
+        struct completion crc_completion;
 };
 
 static size_t mxt_obj_size(const struct mxt_object *obj)
@@ -636,7 +641,7 @@ static void mxt_input_touchevent(struct mxt_data *data,
         }
 }
 
-static unsigned mxt_extract_T6_csum(const u8 *csum)
+static u16 mxt_extract_T6_csum(const u8 *csum)
 {
         return csum[0] | (csum[1] << 8) | (csum[2] << 16);
 }
@@ -654,6 +659,7 @@ static irqreturn_t mxt_process_messages_until_invalid(struct mxt_data *data)
         struct device *dev = &data->client->dev;
         u8 reportid;
         bool update_input = false;
+        u32 crc;
 
         do {
                 if (mxt_read_message(data, &message)) {
@@ -665,9 +671,15 @@ static irqreturn_t mxt_process_messages_until_invalid(struct mxt_data *data)
 
                 if (reportid == data->T6_reportid) {
                         u8 status = payload[0];
-                        unsigned csum = mxt_extract_T6_csum(&payload[1]);
+
+                        crc = mxt_extract_T6_csum(&payload[1]);
+                        if (crc != data->config_crc) {
+                                data->config_crc = crc;
+                                complete(&data->crc_completion);
+                        }
+
                         dev_dbg(dev, "Status: %02x Config Checksum: %06x\n",
-                                status, csum);
+                                status, data->config_crc);
 
                         if (status & MXT_T6_STATUS_RESET)
                                 complete(&data->reset_completion);
@@ -757,6 +769,24 @@ static int mxt_soft_reset(struct mxt_data *data)
         return 0;
 }
 
+static void mxt_update_crc(struct mxt_data *data, u8 cmd, u8 value)
+{
+        /*
+         * On failure, CRC is set to 0 and config will always be
+         * downloaded.
+         */
+        data->config_crc = 0;
+        reinit_completion(&data->crc_completion);
+
+        mxt_t6_command(data, cmd, value, true);
+
+        /*
+         * Wait for crc message. On failure, CRC is set to 0 and config will
+         * always be downloaded.
+         */
+        mxt_wait_for_completion(data, &data->crc_completion, MXT_CRC_TIMEOUT);
+}
+
 static int mxt_check_reg_init(struct mxt_data *data)
 {
         const struct mxt_platform_data *pdata = data->pdata;
@@ -771,6 +801,16 @@ static int mxt_check_reg_init(struct mxt_data *data)
                 return 0;
         }
 
+        mxt_update_crc(data, MXT_COMMAND_REPORTALL, 1);
+
+        if (data->config_crc == pdata->config_crc) {
+                dev_info(dev, "Config CRC 0x%06X: OK\n", data->config_crc);
+                return 0;
+        }
+
+        dev_info(dev, "Config CRC 0x%06X: does not match 0x%06X\n",
+                 data->config_crc, pdata->config_crc);
+
         for (i = 0; i < data->info.object_num; i++) {
                 object = data->object_table + i;
 
@@ -790,6 +830,14 @@ static int mxt_check_reg_init(struct mxt_data *data)
                 index += size;
         }
 
+        mxt_update_crc(data, MXT_COMMAND_BACKUPNV, MXT_BACKUP_VALUE);
+
+        ret = mxt_soft_reset(data);
+        if (ret)
+                return ret;
+
+        dev_info(dev, "Config successfully updated\n");
+
         return 0;
 }
 
@@ -929,11 +977,6 @@ static int mxt_initialize(struct mxt_data *data)
                 goto err_free_object_table;
         }
 
-        error = mxt_t6_command(data, MXT_COMMAND_BACKUPNV,
-                               MXT_BACKUP_VALUE, false);
-        if (!error)
-                mxt_soft_reset(data);
-
         /* Update matrix size at info struct */
         error = mxt_read_reg(client, MXT_MATRIX_X_SIZE, &val);
         if (error)
@@ -1263,6 +1306,7 @@ static int mxt_probe(struct i2c_client *client,
 
         init_completion(&data->bl_completion);
         init_completion(&data->reset_completion);
+        init_completion(&data->crc_completion);
 
         mxt_calc_resolution(data);
 
diff --git a/include/linux/i2c/atmel_mxt_ts.h b/include/linux/i2c/atmel_mxt_ts.h
index d26080dc606c..9f92135b6620 100644
--- a/include/linux/i2c/atmel_mxt_ts.h
+++ b/include/linux/i2c/atmel_mxt_ts.h
@@ -29,6 +29,7 @@
 struct mxt_platform_data {
         const u8 *config;
         size_t config_length;
+        u32 config_crc;
 
         unsigned int x_size;
         unsigned int y_size;