MFD: twl6040: Cache the vibra control registers

The vibra control register will be used from the ASoC codec driver as well.
In order to avoid latency issues caused by I2C read access, cache the two
control register within the core driver, so we do not need to reach out
to the chip to read it back.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/mfd/twl6040-core.c

@@ -34,17 +34,25 @@
 #include <linux/mfd/core.h>
 #include <linux/mfd/twl6040.h>
 
+#define VIBRACTRL_MEMBER(reg) ((reg == TWL6040_REG_VIBCTLL) ? 0 : 1)
+
 int twl6040_reg_read(struct twl6040 *twl6040, unsigned int reg)
 {
 	int ret;
 	u8 val = 0;
 
 	mutex_lock(&twl6040->io_mutex);
+	/* Vibra control registers from cache */
+	if (unlikely(reg == TWL6040_REG_VIBCTLL ||
+		     reg == TWL6040_REG_VIBCTLR)) {
+		val = twl6040->vibra_ctrl_cache[VIBRACTRL_MEMBER(reg)];
+	} else {
 		ret = twl_i2c_read_u8(TWL_MODULE_AUDIO_VOICE, &val, reg);
 		if (ret < 0) {
 			mutex_unlock(&twl6040->io_mutex);
 			return ret;
 		}
+	}
 	mutex_unlock(&twl6040->io_mutex);
 
 	return val;
@@ -57,6 +65,9 @@ int twl6040_reg_write(struct twl6040 *twl6040, unsigned int reg, u8 val)
 
 	mutex_lock(&twl6040->io_mutex);
 	ret = twl_i2c_write_u8(TWL_MODULE_AUDIO_VOICE, val, reg);
+	/* Cache the vibra control registers */
+	if (reg == TWL6040_REG_VIBCTLL || reg == TWL6040_REG_VIBCTLR)
+		twl6040->vibra_ctrl_cache[VIBRACTRL_MEMBER(reg)] = val;
 	mutex_unlock(&twl6040->io_mutex);
 
 	return ret;

include/linux/mfd/twl6040.h

@@ -184,6 +184,7 @@ struct twl6040 {
 	int audpwron;
 	int power_count;
 	int rev;
+	u8 vibra_ctrl_cache[2];
 
 	int pll;
 	unsigned int sysclk;