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[209.132.180.67]) by mx.google.com with ESMTP id 82-v6si16535346pfs.40.2018.05.22.09.37.07; Tue, 22 May 2018 09:37:21 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=fail header.i=@sirena.org.uk header.s=20170815-heliosphere header.b=jIqhb3mG; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752625AbeEVQgW (ORCPT + 99 others); Tue, 22 May 2018 12:36:22 -0400 Received: from heliosphere.sirena.org.uk ([172.104.155.198]:39646 "EHLO heliosphere.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751474AbeEVQgS (ORCPT ); Tue, 22 May 2018 12:36:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sirena.org.uk; s=20170815-heliosphere; h=In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ahaV+2f9ikgW+IWONgJ0BRyh9Pv1i2bat8ptdlp4oXE=; b=jIqhb3mGGwFNUOYer75Q8J0ZQ LyP9wZLiD2eDXOqLMpnn7/fhfKoUi1h4YImku9H9njZh7vlQaTN8Yj8AKNPXM3VrIIxcWBihReEAF BeHlhhkXXuUHxT7I6zdcSY7IW2i3ldVmWqMYunWp91G+5SSvNIZKGBdMsLwoBTC5PJTbw=; Received: from debutante.sirena.org.uk ([2001:470:1f1d:6b5::3] helo=debutante) by heliosphere.sirena.org.uk with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1fLAGh-00025Q-QZ; Tue, 22 May 2018 16:36:11 +0000 Received: from broonie by debutante with local (Exim 4.91) (envelope-from ) id 1fLAGg-0002L3-QH; Tue, 22 May 2018 17:36:10 +0100 Date: Tue, 22 May 2018 17:36:10 +0100 From: Mark Brown To: David Collins Cc: Stephen Boyd , lgirdwood@gmail.com, mark.rutland@arm.com, robh+dt@kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, rnayak@codeaurora.org, ilina@codeaurora.org Subject: Re: [PATCH 1/2] regulator: add QCOM RPMh regulator driver Message-ID: <20180522163610.GD24776@sirena.org.uk> References: <71fab82672524b95632cdb588c16edfc9711866a.1521246069.git.collinsd@codeaurora.org> <152165924074.91116.13025068669916027026@swboyd.mtv.corp.google.com> <493c1f5d-df99-ca68-0f90-a7937a696f5d@codeaurora.org> <152411734938.46528.9676451637772936597@swboyd.mtv.corp.google.com> <20180419120813.GD27188@sirena.org.uk> <38f42537-f801-115a-4120-1344a67a0462@codeaurora.org> <20180424174111.GH22073@sirena.org.uk> <20180517060948.GI20254@sirena.org.uk> <6cb2ac52-258c-332b-e912-809d16e14114@codeaurora.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="/unnNtmY43mpUSKx" Content-Disposition: inline In-Reply-To: <6cb2ac52-258c-332b-e912-809d16e14114@codeaurora.org> X-Cookie: I have not yet begun to byte! User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --/unnNtmY43mpUSKx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, May 17, 2018 at 01:48:41PM -0700, David Collins wrote: > The RPMh hardware is configured by the boot loader. The configuration > does reflect reality; however, it cannot handle all configurations at > initialization time. Specific headroom management typically comes up in > modem usecases for RF supplies that are sensitive to noise. This feature ... > If you really don't like having this feature present in the Linux RPMh > regulator driver, then I'd be ok removing it. It is not required for > SDM845 which the driver is initially targeting. It's certainly going to be easier to review it separately. > >> In the case of XOB managed LDO regulators, the LDOs physically can be > >> configured to different voltages by the bootloader. However, the RPMh > >> interface provides no mechanism for the application processor to read or > >> change that voltage. Therefore, we need a way to specify such voltages in > >> a board specific (as opposed to driver specific) manner (i.e. device tree). > > Is the kernel somehow prevented from varying these voltages? > Yes. Physically, there exists no RPMh register to read or write the > voltage of LDOs managed via XOB. Additionally, the kernel running on the > application processor is blocked from configuring the voltage via a direct > SPMI writes by access permissions that crash the system when violated. *sigh* Please provide feedback on the problems this (and everything else) is causing to the team working on the firmware. The number of issues with this interface compared to anything else we've seen is really noticable, I see what it's trying to do with providing something like the regulator API is doing but there's quite a lot of missing steps in it which cause no end of problems for general purpose software written on top of it. --/unnNtmY43mpUSKx Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAlsERvkACgkQJNaLcl1U h9BRbQf/bak8Har514vMoevNFbyP0Fz49WvI8YBlBfaGXL+7k5tUpz9B0Iu96kJN KqknnwZ9bWkc0RZ+EgyRIDvMS8KwFPJZgXPEkMyp5kp0eADY2iEF4Da0AZ9ENVxY VmOgDkfRedCEat/h8FIbOAln/Ee41tYdzVBGPvppyMe/LL7kHW/Vs1fVoHc2Xyb+ aeoo6h2B6+NyC6qzfa6TaRy8rh2a2xbDWd7QDvSmD3mqSYt9g+E+qDIe3Wx7flj0 iGpgm3WSFJz0YSadqHzMZMwpsnY8daRatsWsJw2u6Z26vkkzViLaojTHg4+iaH0+ xB41uwO+JsJd6Jcxed5Mv9TMSZfVng== =ZpCa -----END PGP SIGNATURE----- --/unnNtmY43mpUSKx--