From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4495953E02; Tue, 27 Feb 2024 07:12:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709017939; cv=none; b=H+dEXSsORHuYz+udsQo8cTC2i6OlHc+w1JccDlSBdxVGgImB/zq3jZB88uRkvTtNV00WX+27gPS9H6MYEljbMGRLdVkUFVeSdf6ehDntnr5Ud+rD/HO00AKkgNcCCBdxD399CX+QrIpGVtIywFHCbGumUQ4ZYCl6JS8Pp47x+Wc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709017939; c=relaxed/simple; bh=/ZlS3JVss0ofKLJzt6zCP6bT652Dlj49VoFRn7/lXnE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PbUpVsQeEI6dPixfy2Bc5iMKTyqszaI4VydqYP09e8olYreJX6fcGylQfFpAXxAkqj8RYglBhnZPBQDBPJ49a7W6XkpYOMJVZUHFZP47mmBDGgUhhGi7d8QpgYpgEIzivjMg2hUVZAfGEloMcY/pHkP2Tb9L8fdZ0M2fxcDMSZ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Y4lMkKQn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Y4lMkKQn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73704C433F1; Tue, 27 Feb 2024 07:12:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709017938; bh=/ZlS3JVss0ofKLJzt6zCP6bT652Dlj49VoFRn7/lXnE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Y4lMkKQnJoH3dc2QJdgSIcV8tRagsw9X3GtjKarMRVzh0NfAbiHhAXIx95CwjAQbu Xo9fTbI7XkMMP7U0GpkJ9D18u0NzQTOmLHVE6h/TJX9gzjAdyn62TB2jTZOElu/10A d3jHvt8X9/oMhmGyL7jKzwYG4nPEYpwom66yLihfDB5XJ15oz/jqE7cLH082aToFKb Y8VQnxNhq1j3zlor4KQH8YQPQ4kDKe+gktWH2FrUzl/gVeocEWjxcFEjTJGGNIpFYE LKBqRws57JSaIFkY5KaFZ/SSFLx5/HaTKzo21i9AFwG2CIq7Cj7aZZUHF1teZsoN1o P1r08YcKMGE0A== Date: Tue, 27 Feb 2024 08:12:15 +0100 From: Wolfram Sang To: Andi Shyti Cc: linux-i2c@vger.kernel.org, devicetree-spec@vger.kernel.org, Rob Herring , Krzysztof Kozlowski , Chris Packham Subject: Re: dtschema: i2c: messy situation about timeouts Message-ID: Mail-Followup-To: Wolfram Sang , Andi Shyti , linux-i2c@vger.kernel.org, devicetree-spec@vger.kernel.org, Rob Herring , Krzysztof Kozlowski , Chris Packham References: Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="KbqwGrd1llsCvBnc" Content-Disposition: inline In-Reply-To: --KbqwGrd1llsCvBnc Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Andi, > > - "i2c-scl-has-clk-low-timeout" > >=20 > > AFAIU this binding tells that the controller can do clock stretching. > > But what for? >=20 > One of the controllers that was sent a while back required some > hardware description because, in some versions, clock stretching > was supported in the hardware. I see. Still, I think this can (and should be handled) with I2C_AQ_NO_CLK_STRETCH. > The naming is a bit fancy, but it depends on the specification > used as a reference; SMBus, I2C, or specific drivers often refer > to it differently. Yes. I'd give I2C specs most importance, controller documentation least. And probably a salt of personal preference :) > > - "i2c-scl-clk-low-timeout-us" > >=20 > > The description says "Number of microseconds the clock line needs to be > > pulled down in order to force a waiting state." What does "forcing a > > waiting state" mean here? I don't understand this description. >=20 > It comes from the specification. The clock stretching is given as > an interval that can be tweaked depending on the hardware. You mean the maximum clock stretching is tweakable? That, in deed, could be a binding in the future, in theory. Yet, it would need support in the client drivers. Like a touchscreen driver which assumes a reset after a certain time of inactivity. > So far I haven't seen anyone using it, though. The MPC driver used it, just for a different purpose. It was used for a timeout of the total transfer. That's a different thing. So, I suggested the conversion. Happy hacking, Wolfram --KbqwGrd1llsCvBnc Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAmXdi0wACgkQFA3kzBSg KbZOehAAl2QMPUg3dviQislT/+HYpnK5WKVFXRt5/KzfdI/nKY5U/c+mcjLxtEcV 3i9jctgQ6v0Ww/8eOj419UDjcUe/FEd9EknmiAngT5vEMMMvRiJI9DlkA3NxtMaz 2tcpYlpZWmnrR2eyvkiHPKascOEM/igjiZl3ThP84TjxeWC+XmxiY5GhrM4DoN9R /B7nhmJT3P330Zrdet770nRv7IbwfzFxKORjRMJKsCYbT0fE/0YS9kSOsUmJSEUQ BAZrJ73mllsj+sSKQHey1Xf8bpofSinnsPKnDZ6QLZfG36Goie1kuGsTZZYRQ9HS vSStpb4nZhCouEQlrmWMGB+FLmLfdS/wkMdw90qaHPR9Nh6IphDB8xxGS6GmZwAk 6oiMgAo6ApVx7t0NaetIVlOphdDV+71vmx/ahmC1irtM/9RKBQ42c88L3qAEFnA/ RHQsLtxiE79HfjOCoLA/5NMAdxkWjGWSniYQkOFlgZDDvvsmNdkdKOdXJjm8Iaua jID81NOOnv9nnb5hJxkqiH0lUTwgClD2D6uOIufVXR0VlmNMUJOMZ63l5LjsJS39 St8b3qvs7b6bSTL2VJ6XNISAV4B6dMZbY0o8SA/D4luUVnC0tiyMjG5ttiIkn/O+ jb4sPpZgodGU9Kwu+KdrYAhoQrmDyScKL1tsXgfjcE62xxaD81Q= =OLtv -----END PGP SIGNATURE----- --KbqwGrd1llsCvBnc--