[PATCH 04/15] iio: adc: at91-sama5d2_adc: update calibration index, validation condition

[Varshini Rajendran <varshini.rajendran@microchip.com>]

Add additional condition for validating the calibration data read from
the OTP through nvmem device interface. Adjust the calibration indexes
of sama7g5 according to the buffer received from the OTP memory.

Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
---
 drivers/iio/adc/at91-sama5d2_adc.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index c3450246730e..d952109a64a9 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -445,6 +445,14 @@ static const struct at91_adc_reg_layout sama7g5_layout = {
 #define at91_adc_writel(st, reg, val)					\
 	writel_relaxed(val, (st)->base + (st)->soc_info.platform->layout->reg)
 
+/*
+ * The calibration data has a TAG to recognize the packet
+ * The tag has a constant value "ACST" with the ASCII
+ * equivalent 0x41435354. This is used to validate the
+ * calibration data obtained from the OTP.
+ */
+#define AT91_TEMP_CALIB_TAG	0x41435354
+
 /**
  * struct at91_adc_platform - at91-sama5d2 platform information struct
  * @layout:		pointer to the reg layout struct
@@ -504,10 +512,10 @@ struct at91_adc_temp_sensor_clb {
  * @AT91_ADC_TS_CLB_IDX_MAX: max index for temperature calibration packet in OTP
  */
 enum at91_adc_ts_clb_idx {
-	AT91_ADC_TS_CLB_IDX_P1 = 2,
-	AT91_ADC_TS_CLB_IDX_P4 = 5,
-	AT91_ADC_TS_CLB_IDX_P6 = 7,
-	AT91_ADC_TS_CLB_IDX_MAX = 19,
+	AT91_ADC_TS_CLB_IDX_P1 = 1,
+	AT91_ADC_TS_CLB_IDX_P4 = 4,
+	AT91_ADC_TS_CLB_IDX_P6 = 6,
+	AT91_ADC_TS_CLB_IDX_MAX = 18,
 };
 
 /* Temperature sensor calibration - Vtemp voltage sensitivity to temperature. */
@@ -2281,7 +2289,7 @@ static int at91_adc_temp_sensor_init(struct at91_adc_state *st,
 		dev_err(dev, "Failed to read calibration data!\n");
 		return PTR_ERR(buf);
 	}
-	if (len < AT91_ADC_TS_CLB_IDX_MAX * 4) {
+	if (len < AT91_ADC_TS_CLB_IDX_MAX * 4  || buf[0] != AT91_TEMP_CALIB_TAG) {
 		dev_err(dev, "Invalid calibration data!\n");
 		ret = -EINVAL;
 		goto free_buf;
-- 
2.34.1