From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21149C433F5 for ; Fri, 10 Dec 2021 11:18:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233117AbhLJLWV (ORCPT ); Fri, 10 Dec 2021 06:22:21 -0500 Received: from www.zeus03.de ([194.117.254.33]:35488 "EHLO mail.zeus03.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237711AbhLJLWU (ORCPT ); Fri, 10 Dec 2021 06:22:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=simple; d=sang-engineering.com; h= date:from:to:cc:subject:message-id:references:mime-version :content-type:in-reply-to; s=k1; bh=2Aqud306rFs88j3dyky/UfXf59yS uJqUHmSVrmdZR2I=; b=qIH3Fs+dCthxL+4Gddomzfhgdc23TO3TG2lYe/tVdsVl OP6Xc4DtvXViVi4xZ0UmoPOkAaZONHbfcW8Q5kpnu+Mz5JPxHoshq8xxvRV5WPSc cfXtfqffh0UyXRfQuFT8O2WV2J5lMk/Msz9xvML9563C8Bq7hdn6BtMcWq9rAU8= Received: (qmail 1443055 invoked from network); 10 Dec 2021 12:18:43 +0100 Received: by mail.zeus03.de with ESMTPSA (TLS_AES_256_GCM_SHA384 encrypted, authenticated); 10 Dec 2021 12:18:43 +0100 X-UD-Smtp-Session: l3s3148p1@wUnA4sjSopEgAQnoAEPjAJzPXF1eIEK3 Date: Fri, 10 Dec 2021 12:18:41 +0100 From: Wolfram Sang To: Linus Walleij Cc: linux-gpio@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Andy Shevchenko , linux-kernel@vger.kernel.org, Jonathan Corbet , Bartosz Golaszewski , linux-doc@vger.kernel.org Subject: Re: [PATCH v5 1/1] gpio: add sloppy logic analyzer using polling Message-ID: Mail-Followup-To: Wolfram Sang , Linus Walleij , linux-gpio@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Andy Shevchenko , linux-kernel@vger.kernel.org, Jonathan Corbet , Bartosz Golaszewski , linux-doc@vger.kernel.org References: <20211123164902.35370-1-wsa+renesas@sang-engineering.com> <20211123164902.35370-2-wsa+renesas@sang-engineering.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ZbgJohPepknqqfKx" Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org --ZbgJohPepknqqfKx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Linus! > I like this patch. I am glad! >=20 > Maybe a small paragraph first saying what this is, the usecase (feel > free to steal, rewrite etc): >=20 > The sloppy logic analyzer will utilize a few GPIO lines in input mode > on a system to rapidly sample these digital lines, which will, if the > Nyquist criteria is met, result in a time series log with approximate > waveforms as they appeared on these lines. >=20 > One way to use it is to analyze external traffic connected to these > GPIO lines with wires (i.e. digital probes), acting as a common logic > analyzer. Well, frankly, with the driver depending on EXPERT, this paragraph seems a tad superfluous to me. But as it came for free and won't hurt, I took the liberty to add this to the beginning of the documentation. > Another thing it can do is to snoop on on-chip peripherals if the I/O > cells of these peripherals can be used in GPIO input mode at the same > time as they are being used as inputs or outputs for the peripheral, > for example it would be possible to scale down the speed of a certain > MMC controller and snoop the traffic between the MMC controller and > the SD card by the sloppy logic analyzer. In the pin control subsystem > such pin controllers are called "non-strict": a certain pin can be > used with a certain peripheral and as a GPIO input line at the same > time. Thanks for pointing out the 'strict' mode. I actually did snoop pins muxed to I2C but I had to use a gpiolib hack for it assuming this was not supported otherwise. Now, I have a one-liner for the Renesas pinctrl driver which makes things work as well. I will work this out with Geert hopefully. Would be really great to have this feature without my hack! That being said, the paragraph above is a bit too long for my taste, I'll see if I can make it more concise. But it should be there, yes. Thanks for your support! Happy hacking, Wolfram --ZbgJohPepknqqfKx Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAmGzN40ACgkQFA3kzBSg KbYDoA//YzZ1PQZYp3ZV9klerZNz8r6wkg4w72xBlW+3z5JUsxVuJLH+JikBgwpF t2LiKCBX0MvHX4a9m1q10bhw6p9qGUFSJFT6Q5stfIycnS3r/U9JmMIEyqp09Yd7 Z4IUUjA40wIkMbJI+YZ70iHYTX1StffmIJQBhMgXcXgk8rwhaY8yafBMFTr/aljU A3SvpD3b+pdIvGomXbOpLfknA4k3+e5U8qQYjdgHfvg4qM6V6DTRUgRjrWVVrcli PqHNMoj3+g7vtlDjDNaeGYM1Ly+dGP6L/qw0gCb4M2+puRwpfYH2BfIGKQ+mx1Q5 dUZA+pJ/GWZSY29BrATGlMcjTb0NdnFYY3fqudyY3JDJP1oKIxNeaKkKwKodzu/5 32VVChWjVCHXy9qvYleY3GSfbSuq7CfSfWqAatm9gXVyxlGOhSACAsjosibaJqUc 0XoX98DM2Ax2fgShuFwSr+j9MiAmp+/GSeS16W4hk5ZNdlghB1yq26r68pi6oZMN tml8Jn7ObbwNrfiAeDiT2BaMwxTVgkvyByWY5CZ3iYKNnhFoG06hhnPqPE65yVoZ dqsRe5II/HI2o0PDQmMfZgmtfpH4zAUZFQjzIoG5JNrGdiGzsed6Fnf+CLNZZBB0 VvgnF15DOm7Js2dVKbkwKG7WpvhekL6JmNuzK/PzIJxUI/+tFlA= =uTq2 -----END PGP SIGNATURE----- --ZbgJohPepknqqfKx--