From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752447AbdLMJm1 (ORCPT ); Wed, 13 Dec 2017 04:42:27 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:54316 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752357AbdLMJmZ (ORCPT ); Wed, 13 Dec 2017 04:42:25 -0500 Date: Wed, 13 Dec 2017 10:42:27 +0100 From: Greg Kroah-Hartman To: Viresh Kumar Cc: Vincent Guittot , Stephen Boyd , Rajendra Nayak , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, robdclark@gmail.com, s.hauer@pengutronix.de, l.stach@pengutronix.de, shawnguo@kernel.org, fabio.estevam@nxp.com, nm@ti.com, xuwei5@hisilicon.com, robh+dt@kernel.org Subject: Re: [PATCH V4 03/12] drivers: Add boot constraints core Message-ID: <20171213094227.GC13194@kroah.com> References: <2868a37e561cab91ba5495a1e14b9548c8e93c3e.1509284255.git.viresh.kumar@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2868a37e561cab91ba5495a1e14b9548c8e93c3e.1509284255.git.viresh.kumar@linaro.org> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 29, 2017 at 07:18:51PM +0530, Viresh Kumar wrote: > Some devices are powered ON by the bootloader before the bootloader > handovers control to Linux. It maybe important for those devices to keep > working until the time a Linux device driver probes the device and > reconfigure its resources. > > A typical example of that can be the LCD controller, which is used by > the bootloaders to show image(s) while the platform is booting into > Linux. The LCD controller can be using some resources, like clk, > regulators, PM domain, etc, that are shared between several devices. > These shared resources should be configured to satisfy need of all the > users. If another device's (X) driver gets probed before the LCD > controller driver in this case, then it may end up reconfiguring these > resources to ranges satisfying the current users (only device X) and > that can make the LCD screen unstable. > > This patch introduces the concept of boot-constraints, which will be set > by the bootloaders and the kernel will satisfy them until the time > driver for such a device is probed (successfully or unsuccessfully). > > The list of boot constraint types is empty for now, and will be > incrementally updated by later patches. > > Only two routines are exposed by the boot constraints core for now: I think we need some documentation somewhere on how to use this, right? thanks, greg k-h