From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-dm3nam03on0047.outbound.protection.outlook.com ([104.47.41.47]:45844 "EHLO NAM03-DM3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751389AbeEPQIA (ORCPT ); Wed, 16 May 2018 12:08:00 -0400 Subject: Re: [PATCH] iio: imu: inv_mpu6050: advertise max and min freqs To: Jean-Baptiste Maneyrol , linux-iio@vger.kernel.org References: <20180515215349.27482-1-mkelly@xevo.com> <379508e0-0e27-6df6-f29d-1f892745c606@invensense.com> From: Martin Kelly Message-ID: <356e12db-bddc-69c2-e3a3-3c9eb7adcef2@xevo.com> Date: Wed, 16 May 2018 09:07:53 -0700 MIME-Version: 1.0 In-Reply-To: <379508e0-0e27-6df6-f29d-1f892745c606@invensense.com> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 05/16/2018 12:51 AM, Jean-Baptiste Maneyrol wrote: > > > On 15/05/2018 23:53, Martin Kelly wrote: >> CAUTION: This email originated from outside of the organization. >> Please make sure the sender is who they say they are and do not click >> links or open attachments unless you recognize the sender and know the >> content is safe. >> >> >> Currently, we allow a minimum FIFO rate of 4 and a max of 1000, but we >> advertise down to only 10 and up to 1000. Expand the advertised range to >> reflect the full available range. >> >> Signed-off-by: Martin Kelly >> --- >>   drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c >> b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c >> index 43fba5f7532b..3f4862f09db3 100644 >> --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c >> +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c >> @@ -799,7 +799,7 @@ static const struct iio_chan_spec >> inv_mpu_channels[] = { >>   }; >> >>   /* constant IIO attribute */ >> -static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 20 50 100 200 500"); >> +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("4 10 20 50 100 200 500 1000"); >>   static IIO_CONST_ATTR(in_anglvel_scale_available, >>                                            "0.000133090 0.000266181 >> 0.000532362 0.001064724"); >>   static IIO_CONST_ATTR(in_accel_scale_available, >> -- >> 2.11.0 >> > > Hello, > > in fact we advertise only frequencies that are supported by the low-pass > filter. Filter bandwidths are: 5Hz, 10Hz, 20Hz, 42Hz (~50), 98Hz (~100), > 188Hz (~200), which are corresponding to a sampling rate of (x2): 10Hz, > 20Hz, ~50Hz, ~200Hz, ~400Hz. Only 500Hz is a little out of specs, since > 400Hz is not a possible frequency. > > You can always set the frequency to any supported values, but you can > suffer from aliasing. > > I strongly suggest we just keep it like it is today. Better not > advertise frequencies that are not correctly filtered. > > JB OK, that makes sense and is fine with me. Perhaps I should instead just add a comment explaining the situation, since I couldn't tell from the code itself.