Input: iqs5xx - eliminate unnecessary register read

Instead of relying on firmware to enable important register fields
and performing read-modify-write operations to additionally enable
the fields the driver cares about, it's much simpler just to write
all of the pertinent fields explicitly.

This avoids an unnecessary register read operation at start-up and
makes way for the iqs5xx_read_byte() helper to be dropped.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Link: https://lore.kernel.org/r/1611002626-5889-8-git-send-email-jeff@labundy.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/touchscreen/iqs5xx.c b/drivers/input/touchscreen/iqs5xx.c
index 127687a..35da66b 100644 (file)
--- a/drivers/input/touchscreen/iqs5xx.c
+++ b/drivers/input/touchscreen/iqs5xx.c
@@ -47,10 +47,13 @@
 #define IQS5XX_SUSPEND         BIT(0)
 #define IQS5XX_RESUME          0
 
-#define IQS5XX_SW_INPUT_EVENT  0x10
-#define IQS5XX_SETUP_COMPLETE  0x40
-#define IQS5XX_EVENT_MODE      0x01
-#define IQS5XX_TP_EVENT                0x04
+#define IQS5XX_SETUP_COMPLETE  BIT(6)
+#define IQS5XX_WDT             BIT(5)
+#define IQS5XX_ALP_REATI       BIT(3)
+#define IQS5XX_REATI           BIT(2)
+
+#define IQS5XX_TP_EVENT                BIT(2)
+#define IQS5XX_EVENT_MODE      BIT(0)
 
 #define IQS5XX_PROD_NUM                0x0000
 #define IQS5XX_SYS_INFO0       0x000F
@@ -187,11 +190,6 @@ static int iqs5xx_read_word(struct i2c_client *client, u16 reg, u16 *val)
        return 0;
 }
 
-static int iqs5xx_read_byte(struct i2c_client *client, u16 reg, u8 *val)
-{
-       return iqs5xx_read_burst(client, reg, val, sizeof(*val));
-}
-
 static int iqs5xx_write_burst(struct i2c_client *client,
                              u16 reg, const void *val, u16 len)
 {
@@ -561,7 +559,6 @@ static int iqs5xx_dev_init(struct i2c_client *client)
        struct iqs5xx_private *iqs5xx = i2c_get_clientdata(client);
        struct iqs5xx_dev_id_info *dev_id_info;
        int error;
-       u8 val;
        u8 buf[sizeof(*dev_id_info) + 1];
 
        error = iqs5xx_read_burst(client, IQS5XX_PROD_NUM,
@@ -628,18 +625,14 @@ static int iqs5xx_dev_init(struct i2c_client *client)
        if (error)
                return error;
 
-       error = iqs5xx_read_byte(client, IQS5XX_SYS_CFG0, &val);
-       if (error)
-               return error;
-
-       val |= IQS5XX_SETUP_COMPLETE;
-       val &= ~IQS5XX_SW_INPUT_EVENT;
-       error = iqs5xx_write_byte(client, IQS5XX_SYS_CFG0, val);
+       error = iqs5xx_write_byte(client, IQS5XX_SYS_CFG0,
+                                 IQS5XX_SETUP_COMPLETE | IQS5XX_WDT |
+                                 IQS5XX_ALP_REATI | IQS5XX_REATI);
        if (error)
                return error;
 
-       val = IQS5XX_TP_EVENT | IQS5XX_EVENT_MODE;
-       error = iqs5xx_write_byte(client, IQS5XX_SYS_CFG1, val);
+       error = iqs5xx_write_byte(client, IQS5XX_SYS_CFG1,
+                                 IQS5XX_TP_EVENT | IQS5XX_EVENT_MODE);
        if (error)
                return error;