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iio: at91_adc: add low and high res support 

at91 adc offers the choice between two resolutions: low and high.
The low and high resolution values depends on adc IP version, as many IP
properties have been exposed through device tree, these settings have also
been added to the dt bindings.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Ludovic Desroches 2013-03-29 14:54:00 +00:00 committed by Jonathan Cameron
parent 2fc72cd835
commit 47be16b668
2 changed files with 81 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
Documentation/devicetree/bindings/arm/atmel-adc.txt
View File

@ -14,9 +14,17 @@ Required properties:
- atmel,adc-status-register: Offset of the Interrupt Status Register
- atmel,adc-trigger-register: Offset of the Trigger Register
- atmel,adc-vref: Reference voltage in millivolts for the conversions
- atmel,adc-res: List of resolution in bits supported by the ADC. List size
must be two at least.
- atmel,adc-res-names: Contains one identifier string for each resolution
in atmel,adc-res property. "lowres" and "highres"
identifiers are required.
Optional properties:
- atmel,adc-use-external: Boolean to enable of external triggers
- atmel,adc-use-res: String corresponding to an identifier from
atmel,adc-res-names property. If not specified, the highest
resolution will be used.
Optional trigger Nodes:
- Required properties:
@ -40,6 +48,9 @@ adc0: adc@fffb0000 {
atmel,adc-trigger-register = <0x08>;
atmel,adc-use-external;
atmel,adc-vref = <3300>;
atmel,adc-res = <8 10>;
atmel,adc-res-names = "lowres", "highres";
atmel,adc-use-res = "lowres";
trigger@0 {
trigger-name = "external-rising";

74
drivers/iio/adc/at91_adc.c
View File

@ -57,6 +57,8 @@ struct at91_adc_state {
u32 trigger_number;
bool use_external;
u32 vref_mv;
u32 res; /* resolution used for convertions */
bool low_res; /* the resolution corresponds to the lowest one */
wait_queue_head_t wq_data_avail;
};
@ -138,7 +140,7 @@ static int at91_adc_channel_init(struct iio_dev *idev)
chan->channel = bit;
chan->scan_index = idx;
chan->scan_type.sign = 'u';
chan->scan_type.realbits = 10;
chan->scan_type.realbits = st->res;
chan->scan_type.storagebits = 16;
chan->info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE);
chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
@ -372,6 +374,59 @@ static int at91_adc_read_raw(struct iio_dev *idev,
return -EINVAL;
}
static int at91_adc_of_get_resolution(struct at91_adc_state *st,
struct platform_device *pdev)
{
struct iio_dev *idev = iio_priv_to_dev(st);
struct device_node *np = pdev->dev.of_node;
int count, i, ret = 0;
char *res_name, *s;
u32 *resolutions;
count = of_property_count_strings(np, "atmel,adc-res-names");
if (count < 2) {
dev_err(&idev->dev, "You must specified at least two resolution names for "
"adc-res-names property in the DT\n");
return count;
}
resolutions = kmalloc(count * sizeof(*resolutions), GFP_KERNEL);
if (!resolutions)
return -ENOMEM;
if (of_property_read_u32_array(np, "atmel,adc-res", resolutions, count)) {
dev_err(&idev->dev, "Missing adc-res property in the DT.\n");
ret = -ENODEV;
goto ret;
}
if (of_property_read_string(np, "atmel,adc-use-res", (const char **)&res_name))
res_name = "highres";
for (i = 0; i < count; i++) {
if (of_property_read_string_index(np, "atmel,adc-res-names", i, (const char **)&s))
continue;
if (strcmp(res_name, s))
continue;
st->res = resolutions[i];
if (!strcmp(res_name, "lowres"))
st->low_res = true;
else
st->low_res = false;
dev_info(&idev->dev, "Resolution used: %u bits\n", st->res);
goto ret;
}
dev_err(&idev->dev, "There is no resolution for %s\n", res_name);
ret:
kfree(resolutions);
return ret;
}
static int at91_adc_probe_dt(struct at91_adc_state *st,
struct platform_device *pdev)
{
@ -415,6 +470,10 @@ static int at91_adc_probe_dt(struct at91_adc_state *st,
}
st->vref_mv = prop;
ret = at91_adc_of_get_resolution(st, pdev);
if (ret)
goto error_ret;
st->registers = devm_kzalloc(&idev->dev,
sizeof(struct at91_adc_reg_desc),
GFP_KERNEL);
@ -628,9 +687,16 @@ static int at91_adc_probe(struct platform_device *pdev)
*/
ticks = round_up((st->startup_time * adc_clk /
1000000) - 1, 8) / 8;
at91_adc_writel(st, AT91_ADC_MR,
(AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL) |
(AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP));
if (st->low_res)
at91_adc_writel(st, AT91_ADC_MR,
AT91_ADC_LOWRES |
(AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL) |
(AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP));
else
at91_adc_writel(st, AT91_ADC_MR,
(AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL) |
(AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP));
/* Setup the ADC channels available on the board */
ret = at91_adc_channel_init(idev);