Harald Geyer schrieb am 29.06.2015 um 20:59:
> Hi Jonathan!
>
> Jonathan Cameron writes:
>> On 07/04/15 12:12, Harald Geyer wrote:
>>> This cleans up the most ugly workaround in this driver. There are no
>>> functional changes yet in the decoding algorithm, but we improve the
>>> following things:
>>> * Get rid of spurious warning messages on systems with fast HRTIMER.
>>> * If the clock is not fast enough for decoding to work, we give
>>> up immediately.
>>> * In that case we return EAGAIN instead of EIO, so it's easier to
>>> discriminate causes of failure.
>>>
>>> Returning EAGAIN is somewhat controversial: It's technically correct
>>> as a faster clock might become available. OTOH once all clocks are
>>> enabled this is a permanent error. There is no ECLOCKTOOSLOW error
>>> code.
>>>
>>> Signed-off-by: Harald Geyer <harald@xxxxxxxxx>
>> Looks good to me. Will wait for comments on the first patch though
>> before taking this... clearly that one will need a few acks if I take
>> it through IIO!
>
> The first patch has been merged via tip tree for 4.2 (is already available
> in staging-next tree). Are you going to pick up this patch or do I need
> to resend?
>
> Thanks,
> Harald
>
Hi Harald,
there are a few small style issues, which checkpatch.pl --strict should
show you. It would be good to have them eliminated before this patch
gets applied.
Thanks,
Hartmut
>> Jonathan
>>> ---
>>> changes since V1:
>>> call ktime_get_xxx() functions directly instead of using the wrappers
>>> of the iio subsystem.
>>>
>>> drivers/iio/humidity/dht11.c | 42 ++++++++++++++++++++++--------------------
>>> 1 files changed, 22 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
>>> index 7d79a1a..4cb25dc 100644
>>> --- a/drivers/iio/humidity/dht11.c
>>> +++ b/drivers/iio/humidity/dht11.c
>>> @@ -33,6 +33,7 @@
>>> #include <linux/delay.h>
>>> #include <linux/gpio.h>
>>> #include <linux/of_gpio.h>
>>> +#include <linux/timekeeping.h>
>>>
>>> #include <linux/iio/iio.h>
>>>
>>> @@ -87,23 +88,11 @@ static unsigned char dht11_decode_byte(int *timing, int threshold)
>>> return ret;
>>> }
>>>
>>> -static int dht11_decode(struct dht11 *dht11, int offset)
>>> +static int dht11_decode(struct dht11 *dht11, int offset, int timeres)
>>> {
>>> - int i, t, timing[DHT11_BITS_PER_READ], threshold,
>>> - timeres = DHT11_SENSOR_RESPONSE;
>>> + int i, t, timing[DHT11_BITS_PER_READ], threshold;
>>> unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
>>>
>>> - /* Calculate timestamp resolution */
>>> - for (i = 1; i < dht11->num_edges; ++i) {
>>> - t = dht11->edges[i].ts - dht11->edges[i-1].ts;
>>> - if (t > 0 && t < timeres)
>>> - timeres = t;
>>> - }
>>> - if (2*timeres > DHT11_DATA_BIT_HIGH) {
>>> - pr_err("dht11: timeresolution %d too bad for decoding\n",
>>> - timeres);
>>> - return -EIO;
>>> - }
>>> threshold = DHT11_DATA_BIT_HIGH / timeres;
>>> if (DHT11_DATA_BIT_LOW/timeres + 1 >= threshold)
>>> pr_err("dht11: WARNING: decoding ambiguous\n");
>>> @@ -126,7 +115,7 @@ static int dht11_decode(struct dht11 *dht11, int offset)
>>> if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum)
>>> return -EIO;
>>>
>>> - dht11->timestamp = iio_get_time_ns();
>>> + dht11->timestamp = ktime_get_real_ns();
>>> if (hum_int < 20) { /* DHT22 */
>>> dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
>>> ((temp_int & 0x80) ? -100 : 100);
>>> @@ -154,7 +143,7 @@ static irqreturn_t dht11_handle_irq(int irq, void *data)
>>>
>>> /* TODO: Consider making the handler safe for IRQ sharing */
>>> if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
>>> - dht11->edges[dht11->num_edges].ts = iio_get_time_ns();
>>> + dht11->edges[dht11->num_edges].ts = ktime_get_real_ns();
>>> dht11->edges[dht11->num_edges++].value =
>>> gpio_get_value(dht11->gpio);
>>>
>>> @@ -170,10 +159,22 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
>>> int *val, int *val2, long m)
>>> {
>>> struct dht11 *dht11 = iio_priv(iio_dev);
>>> - int ret;
>>> + int ret, timeres;
>>>
>>> mutex_lock(&dht11->lock);
>>> - if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) {
>>> + if (dht11->timestamp + DHT11_DATA_VALID_TIME < ktime_get_real_ns()) {
>>> + timeres = ktime_get_resolution_ns();
>>> + if (DHT11_DATA_BIT_HIGH < 2*timeres) {
>>> + dev_err(dht11->dev, "timeresolution %dns too low\n",
>>> + timeres);
>>> + /* In theory a better clock could become available
>>> + * at some point ... and there is no error code
>>> + * that really fits better.
>>> + */
>>> + ret = -EAGAIN;
>>> + goto err;
>>> + }
>>> +
>>> reinit_completion(&dht11->completion);
>>>
>>> dht11->num_edges = 0;
>>> @@ -208,7 +209,8 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
>>> ret = dht11_decode(dht11,
>>> dht11->num_edges == DHT11_EDGES_PER_READ ?
>>> DHT11_EDGES_PREAMBLE :
>>> - DHT11_EDGES_PREAMBLE - 2);
>>> + DHT11_EDGES_PREAMBLE - 2,
>>> + timeres);
>>> if (ret)
>>> goto err;
>>> }
>>> @@ -274,7 +276,7 @@ static int dht11_probe(struct platform_device *pdev)
>>> return -EINVAL;
>>> }
>>>
>>> - dht11->timestamp = iio_get_time_ns() - DHT11_DATA_VALID_TIME - 1;
>>> + dht11->timestamp = ktime_get_real_ns() - DHT11_DATA_VALID_TIME - 1;
>>> dht11->num_edges = -1;
>>>
>>> platform_set_drvdata(pdev, iio);
>>>
>>
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