mfd: twl-core: Add API to query the HFCLK rate

CFG_BOOT register's HFCLK_FREQ field hold information about the used HFCLK
frequency.
Add possibility for users to get the configured rate based on this
register.
This register was configured during boot, without it the chip would not
operate correctly, so we can trust on this information.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/twl-core.c

@@ -552,6 +552,38 @@ int twl_get_version(void)
 }
 EXPORT_SYMBOL_GPL(twl_get_version);
 
+/**
+ * twl_get_hfclk_rate - API to get TWL external HFCLK clock rate.
+ *
+ * Api to get the TWL HFCLK rate based on BOOT_CFG register.
+ */
+int twl_get_hfclk_rate(void)
+{
+	u8 ctrl;
+	int rate;
+
+	twl_i2c_read_u8(TWL_MODULE_PM_MASTER, &ctrl, R_CFG_BOOT);
+
+	switch (ctrl & 0x3) {
+	case HFCLK_FREQ_19p2_MHZ:
+		rate = 19200000;
+		break;
+	case HFCLK_FREQ_26_MHZ:
+		rate = 26000000;
+		break;
+	case HFCLK_FREQ_38p4_MHZ:
+		rate = 38400000;
+		break;
+	default:
+		pr_err("TWL4030: HFCLK is not configured\n");
+		rate = -EINVAL;
+		break;
+	}
+
+	return rate;
+}
+EXPORT_SYMBOL_GPL(twl_get_hfclk_rate);
+
 static struct device *
 add_numbered_child(unsigned chip, const char *name, int num,
 		void *pdata, unsigned pdata_len,

include/linux/i2c/twl.h

@@ -188,6 +188,7 @@ int twl_i2c_read(u8 mod_no, u8 *value, u8 reg, unsigned num_bytes);
 
 int twl_get_type(void);
 int twl_get_version(void);
+int twl_get_hfclk_rate(void);
 
 int twl6030_interrupt_unmask(u8 bit_mask, u8 offset);
 int twl6030_interrupt_mask(u8 bit_mask, u8 offset);