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[72.189.64.225]) by smtp.gmail.com with ESMTPSA id f202sm13683253qke.112.2020.11.17.04.25.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Nov 2020 04:25:48 -0800 (PST) Date: Tue, 17 Nov 2020 07:25:41 -0500 From: William Breathitt Gray To: Ahmad Fatoum Cc: Benjamin Gaignard , Fabrice Gasnier , Pengutronix Kernel Team , Holger Assmann , "linux-stm32@st-md-mailman.stormreply.com" , Alexandre Torgue , linux-iio@vger.kernel.org Subject: Re: Counter device Interface for reading out input capture Message-ID: References: <20201106124217.GA4015@shinobu> <0fa25b7a-92f9-8eb7-088e-2ef3a2edf2a0@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="nSRaz29Y8MvsNho9" Content-Disposition: inline In-Reply-To: <0fa25b7a-92f9-8eb7-088e-2ef3a2edf2a0@pengutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org --nSRaz29Y8MvsNho9 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Nov 17, 2020 at 11:54:17AM +0100, Ahmad Fatoum wrote: > Hello William, >=20 > On 06.11.20 13:42, William Breathitt Gray wrote: > > On Thu, Nov 05, 2020 at 07:46:14PM +0100, Ahmad Fatoum wrote: > >> It doesn't look like the counter device API is yet made to support such > >> an input capture mode (latching a counter value on an external event, = e.g. > >> to timestamp incoming rising edges to measure jitter between pulses). > > > > Regarding the Counter subsystem, I'm developing a Counter character > > device API that supports timestamps for counter devices: > > https://lore.kernel.org/linux-arm-kernel/157d1edf-feec-33b5-7ad5-94f993= 16ca6e@lechnology.com/T/ >=20 > Any chance we could have a "raw" timestamp as well like the network > stack offers (cf. SOF_TIMESTAMPING_{RAW,SYS}_HARDWARE)? >=20 > The API currently only exposes a ktime (i.e. CLOCK_MONOTONIC), which the > raw timer count can't be readily converted to. For our use case of > measuring jitter, the raw value is sufficient. Sure, we can add support for a "raw" timestamp. I can see how this could be more useful in certain circumstances rather than the ktime value. I'll open a discussion about it when I submit the next revision of the Counter character device patchset. :-) William Breathitt Gray --nSRaz29Y8MvsNho9 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEk5I4PDJ2w1cDf/bghvpINdm7VJIFAl+zwTAACgkQhvpINdm7 VJJYTQ/+PfehxFKZUm1Zo/rIlQG7MY2iPsOOAwVrwt/jAl0dIRd68h/68ZFoT0/p +hVVClbTv/TwNIAyJLgFHS6UNAJlYx9pU1sbVtyzzGDD4H83u1lfdUeO+9t3DvBy qRmlVZrv2Shl9eIJvChVPupOv8E+DYyG8uIIXKzAakF8bQeFGiI611mV3s4rDDEW 1MiygpAN81LZmTP3h3wVV4uClvI+MliGBCGPv5BjYjSl3tnqAvSjFjsOiNovD9ue OFQUkZQbpEBaQWuIpGL5i6YZEfpYp084AWoXhOiIhQjAQTY+V2RQ4ADp4wsLNodf kEBdZ0FLJx1rrhm4iDAaWMxs7vCo/pVH0bB2ZNv2vqbAUjIM5+g0rRgGdvd53DMI 1Y8+l+DFPraDB7mbM6Gp36pQIABzQc/0K9oq++g4h12q8H/gmsEb004C0GMP1fsF zosN+xYqGvBjiwq7Doq4n8mU3Batwz5+WxtoKBM7m3TX/OykSbB3ne0yGPjGGM1u SepLf4E+GLNqHHdmbXj6/Vsq4qaeEk7vDUs12BPNvrX/AnfLzLcdCBI21Ln0sv8B UbKYOghdfjA31mRltI4tDtpujgm1euhDDGE+ebZK/JcYzoBfl9tpPtd1dDrp3Qx5 IOc7cqPKybWsTDiwuWw/l31953+aX9hYZsHs6b0PpdKhBN7bN7w= =lBqg -----END PGP SIGNATURE----- --nSRaz29Y8MvsNho9--