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authorJosh Wu <josh.wu@atmel.com>2013-10-08 04:48:00 +0100
committerJonathan Cameron <jic23@kernel.org>2013-10-09 21:15:32 +0100
commitc46016665fff1dcf08d6046cee45c98781996567 (patch)
treedf8aa9fcf9b8e7c274d39f6de70bfd7b0769a5bc /drivers/iio/adc
parentedf7abde26cd2625fe17a1a1f6a35aa758f72cd0 (diff)
downloadlinux-c46016665fff1dcf08d6046cee45c98781996567.tar.bz2
iio: at91: ADC start-up time calculation changed since at91sam9x5
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@atmel.com> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Diffstat (limited to 'drivers/iio/adc')
-rw-r--r--drivers/iio/adc/at91_adc.c53
1 files changed, 46 insertions, 7 deletions
diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 8b93295369b0..abce01b9ff91 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -40,6 +40,9 @@
(writel_relaxed(val, st->reg_base + reg))
struct at91_adc_caps {
+ /* startup time calculate function */
+ u32 (*calc_startup_ticks)(u8 startup_time, u32 adc_clk_khz);
+
struct at91_adc_reg_desc registers;
};
@@ -428,6 +431,45 @@ ret:
return ret;
}
+static u32 calc_startup_ticks_9260(u8 startup_time, u32 adc_clk_khz)
+{
+ /*
+ * 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
+ */
+ return round_up((startup_time * adc_clk_khz / 1000) - 1, 8) / 8;
+}
+
+static u32 calc_startup_ticks_9x5(u8 startup_time, u32 adc_clk_khz)
+{
+ /*
+ * 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);
+ unsigned int ticks;
+
+ ticks = 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;
+
+ return ticks;
+}
+
static const struct of_device_id at91_adc_dt_ids[];
static int at91_adc_probe_dt(struct at91_adc_state *st,
@@ -651,15 +693,9 @@ static int at91_adc_probe(struct platform_device *pdev)
ret = -EINVAL;
goto error_disable_adc_clk;
}
+ ticks = (*st->caps->calc_startup_ticks)(st->startup_time, adc_clk_khz);
/*
- * 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;
- /*
* a minimal Sample and Hold Time is necessary for the ADC to guarantee
* the best converted final value between two channels selection
* The formula thus is : Sample and Hold Time = (shtim + 1) / ADCClock
@@ -736,6 +772,7 @@ static int at91_adc_remove(struct platform_device *pdev)
#ifdef CONFIG_OF
static struct at91_adc_caps at91sam9260_caps = {
+ .calc_startup_ticks = calc_startup_ticks_9260,
.registers = {
.channel_base = AT91_ADC_CHR(0),
.drdy_mask = AT91_ADC_DRDY,
@@ -747,6 +784,7 @@ static struct at91_adc_caps at91sam9260_caps = {
};
static struct at91_adc_caps at91sam9g45_caps = {
+ .calc_startup_ticks = calc_startup_ticks_9260, /* same as 9260 */
.registers = {
.channel_base = AT91_ADC_CHR(0),
.drdy_mask = AT91_ADC_DRDY,
@@ -758,6 +796,7 @@ static struct at91_adc_caps at91sam9g45_caps = {
};
static struct at91_adc_caps at91sam9x5_caps = {
+ .calc_startup_ticks = calc_startup_ticks_9x5,
.registers = {
.channel_base = AT91_ADC_CDR0_9X5,
.drdy_mask = AT91_ADC_SR_DRDY_9X5,