From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from saturn.retrosnub.co.uk ([46.235.226.198]:60228 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750932AbeETK2m (ORCPT ); Sun, 20 May 2018 06:28:42 -0400 Date: Sun, 20 May 2018 11:28:38 +0100 From: Jonathan Cameron To: Martin Kelly Cc: Jean-Baptiste Maneyrol , linux-iio@vger.kernel.org Subject: Re: [PATCH] iio: imu: inv_mpu6050: advertise max and min freqs Message-ID: <20180520112838.3149f0f1@archlinux> In-Reply-To: <356e12db-bddc-69c2-e3a3-3c9eb7adcef2@xevo.com> References: <20180515215349.27482-1-mkelly@xevo.com> <379508e0-0e27-6df6-f29d-1f892745c606@invensense.com> <356e12db-bddc-69c2-e3a3-3c9eb7adcef2@xevo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On Wed, 16 May 2018 09:07:53 -0700 Martin Kelly wrote: > 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. Hmm. If this wasn't already the case I would advocate never allowing the user to pick frequencies where the device effectively won't work properly. Ah well, too late now as they are in the ABI. Agreed a comment would avoid anyone trying to figure this out in future. Jonathan > -- > To unsubscribe from this list: send the line "unsubscribe linux-iio" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html