Since in at91sam9x5, sama5d3x chip. the start up time calucation is changed.
This patch can choose different start up time calculation formula for different
chips.
Signed-off-by: Josh Wu <josh.wu@xxxxxxxxx>
---
v1 --> v2:
add a new variable for different start_time calculation.
drivers/iio/adc/at91_adc.c | 42 +++++++++++++++++++++++++++++++++++-------
1 file changed, 35 insertions(+), 7 deletions(-)
diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index b41eb60..9b0ffff 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -40,6 +40,7 @@
(writel_relaxed(val, st->reg_base + reg))
struct at91_adc_caps {
+ bool start_time_use_lookup_tab;
u32 mr_prescal_mask;
u32 mr_startup_mask;
};
@@ -700,13 +701,39 @@ static int at91_adc_probe(struct platform_device *pdev)
goto error_disable_adc_clk;
}
- /*
- * Number of ticks needed to cover the startup time of the ADC as
- * defined in the electrical characteristics of the board, divided by 8.
- * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock
- */
- ticks = round_up((st->startup_time * adc_clk_khz /
- 1000) - 1, 8) / 8;
+ if (!st->caps->start_time_use_lookup_tab) {
+ /*
+ * Number of ticks needed to cover the startup time of the ADC
+ * as defined in the electrical characteristics of the board,
+ * divided by 8. The formula thus is :
+ * Startup Time = (ticks + 1) * 8 / ADC Clock
+ */
+ ticks = round_up((st->startup_time * adc_clk_khz /
+ 1000) - 1, 8) / 8;
+ } else {
+ /*
+ * For sama5d3x and at91sam9x5, the formula changes to:
+ * Startup Time = <lookup_table_value> / ADC Clock
+ */
+ const int startup_lookup[] = {
+ 0 , 8 , 16 , 24 ,
+ 64 , 80 , 96 , 112,
+ 512, 576, 640, 704,
+ 768, 832, 896, 960
+ };
+
+ int i, size = ARRAY_SIZE(startup_lookup);
+ ticks = st->startup_time * adc_clk_khz / 1000;
+ for (i = 0; i < size; i++)
+ if (ticks < startup_lookup[i])
+ break;
+
+ ticks = i;
+ if (ticks == size)
+ /* Reach the end of lookup table */
+ ticks = size - 1;
+ }
+
/*
* a minimal Sample and Hold Time is necessary for the ADC to guarantee
* the best converted final value between two channels selection
@@ -798,6 +825,7 @@ static struct at91_adc_caps at91sam9g45_caps = {
};
static struct at91_adc_caps at91sam9x5_caps = {
+ .start_time_use_lookup_tab = true,
.mr_prescal_mask = AT91_ADC_PRESCAL_9G45, /* same as 9G45 */
.mr_startup_mask = AT91_ADC_STARTUP_9X5,
};
--
1.7.10
--
To unsubscribe from this list: send the line "unsubscribe linux-iio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
