From patchwork Fri Jul 8 07:44:31 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dirk Behme X-Patchwork-Id: 9220121 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A9D8360574 for ; Fri, 8 Jul 2016 07:44:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9CA4D28327 for ; Fri, 8 Jul 2016 07:44:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9098128555; Fri, 8 Jul 2016 07:44:58 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E75CA28327 for ; Fri, 8 Jul 2016 07:44:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754016AbcGHHor (ORCPT ); Fri, 8 Jul 2016 03:44:47 -0400 Received: from smtp6-v.fe.bosch.de ([139.15.237.11]:56402 "EHLO smtp6-v.fe.bosch.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754009AbcGHHoo (ORCPT ); Fri, 8 Jul 2016 03:44:44 -0400 Received: from vsmta13.fe.internet.bosch.com (unknown [10.4.98.53]) by imta24.fe.bosch.de (Postfix) with ESMTP id 1847ED80212; Fri, 8 Jul 2016 09:44:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=de.bosch.com; s=2015-01-21; t=1467963882; bh=DwknhTotxl+1GITfrhW3aC3RD0EWbkd0dc6FC5+ual8=; l=10; h=From:From:Reply-To:Sender; b=V37FCKRunpcPm/O00LlPA0FDxXWwlI/SStp6IJW11Vquwde9hqV4ZlNniRRkkQERx fkhmBq3T7Gn3xW1qROUyCZ3T/M/WUsAkrV1T171PXCYjD5rFCYZ1OwXzw4LCd226Gy /ugXqm+8I3HBNJ7LHoxNxVGS5VbrkQKFzr8ua6pc= Received: from FE-HUB1000.de.bosch.com (vsgw23.fe.internet.bosch.com [10.4.98.23]) by vsmta13.fe.internet.bosch.com (Postfix) with ESMTP id B005D2E4037E; Fri, 8 Jul 2016 09:44:41 +0200 (CEST) Received: from hi-z08if.hi.de.bosch.com (10.34.209.31) by FE-HUB1000.de.bosch.com (10.4.103.107) with Microsoft SMTP Server id 14.3.195.1; Fri, 8 Jul 2016 09:44:40 +0200 Received: from hi-z08if.hi.de.bosch.com (localhost [127.0.0.1]) by hi-z08if.hi.de.bosch.com (Postfix) with ESMTP id E6768624283; Fri, 8 Jul 2016 09:44:32 +0200 (CEST) From: Dirk Behme To: , Julien Grall , Mark Rutland , Michael Turquette CC: , , Stefano Stabellini , , Stephen Boyd , Dirk Behme Subject: [PATCH v3] xen/arm: enable clocks used by the hypervisor Date: Fri, 8 Jul 2016 09:44:31 +0200 Message-ID: <1467963871-31556-1-git-send-email-dirk.behme@de.bosch.com> X-Mailer: git-send-email 2.8.0 MIME-Version: 1.0 X-TM-AS-MML: disable X-TM-AS-Product-Ver: IMSS-7.1.0.1679-8.0.0.1202-22436.006 X-TMASE-MatchedRID: K8thoRlNrQUNzLbygMeXAh3EEAbn+GRboprEeoZHCQLk3GeNbRoaNhlN xiPQSlnnBdWRKqwklojDpxqo7r+PMhNmUW1dq3NxsyNb+yeIRAqy4iyjvVWTomHZ+cd7VyKXwbD ngUleUcJVbmUBto85MLXJ7NiG0ChHD0VXqQ1iI8cve6W+IORwrQRryDXHx6oXWltirZ/iPP7A88 QtBabi+dT6ykxLQSF+MCL4p+6WzsoYGe03I+tEGw5KPhGIg0MRFuNF4lJG6xtMkxalJcuged/9N 6lK9KH6CNLuPteRDHd+UFigpiFI09TO9w9KisCUk3ewifG2MNOiegRrH8ppLPLKGfm7ex0q53R6 SzAazpqY8waFvdc6FA7cTtEjrga7mtuznbq2AqwVglQa/gMvfJYcYQ11P5U/JLfQYoCQHFbieaD XCgNTtr45yxeoB10KgDLqnrRlXrZ8nn9tnqel2DsAVzN+Ov/sHD3lxBPiGdb/a4q5qQq0IvJjn5 5rOUmVmNMZOQvqYFlnwJvCVeSeYA== Sender: linux-clk-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Xen hypervisor drivers might replace native OS drivers. The result is that some important clocks that are enabled by the OS in the non-Xen case are not properly enabled in the presence of Xen. The clocks property enumerates the clocks that must be enabled by the Xen clock consumer. An example is a serial driver enabled by the hypervisor. Xen must consume and enable these clocks in the OS to ensure behavior continues after firmware configures the UART hardware and corresponding clock harder. Up to now, the workaround for this has been to use the Linux kernel command line parameter 'clk_ignore_unused'. See Xen bug http://bugs.xenproject.org/xen/bug/45 too. To fix this, we will add the "unused" clocks in Xen to the hypervisor node. The OS has to consume and enable the clocks from the hypervisor node, then. Therefore, check if there is a "clocks" entry in the hypervisor node and if so consume and enable the given clocks. This prevents the clocks from being disabled by the OS. Signed-off-by: Dirk Behme --- Changes in v3: Use the xen.txt description proposed by Michael. Thanks! Changes in v2: Drop the Linux implementation details like clk_disable_unused in xen.txt. Documentation/devicetree/bindings/arm/xen.txt | 13 ++++++++ arch/arm/xen/enlighten.c | 47 +++++++++++++++++++++++++++ 2 files changed, 60 insertions(+) diff --git a/Documentation/devicetree/bindings/arm/xen.txt b/Documentation/devicetree/bindings/arm/xen.txt index c9b9321..00f2165 100644 --- a/Documentation/devicetree/bindings/arm/xen.txt +++ b/Documentation/devicetree/bindings/arm/xen.txt @@ -17,6 +17,19 @@ the following properties: A GIC node is also required. This property is unnecessary when booting Dom0 using ACPI. +Optional properties: + +clocks: one or more clocks to be enabled + Xen hypervisor drivers might replace native OS drivers. The result is + that some important clocks that are enabled by the OS in the non-Xen + case are not properly enabled in the presence of Xen. The clocks + property enumerates the clocks that must be enabled by the Xen clock + consumer. + An example is a serial driver enabled by the hypervisor. Xen must + consume and enable these clocks in the OS to ensure behavior continues + after firmware configures the UART hardware and corresponding clock + harder. + To support UEFI on Xen ARM virtual platforms, Xen populates the FDT "uefi" node under /hypervisor with following parameters: diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c index 47acb36..5c546d0 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include @@ -444,6 +445,52 @@ static int __init xen_pm_init(void) } late_initcall(xen_pm_init); +/* + * Check if we want to register some clocks, that they + * are not freed because unused by clk_disable_unused(). + * E.g. the serial console clock. + */ +static int __init xen_arm_register_clks(void) +{ + struct clk *clk; + struct device_node *xen_node; + unsigned int i, count; + int ret = 0; + + xen_node = of_find_compatible_node(NULL, NULL, "xen,xen"); + if (!xen_node) { + pr_err("Xen support was detected before, but it has disappeared\n"); + return -EINVAL; + } + + count = of_clk_get_parent_count(xen_node); + if (!count) + goto out; + + for (i = 0; i < count; i++) { + clk = of_clk_get(xen_node, i); + if (IS_ERR(clk)) { + pr_err("Xen failed to register clock %i. Error: %li\n", + i, PTR_ERR(clk)); + ret = PTR_ERR(clk); + goto out; + } + + ret = clk_prepare_enable(clk); + if (ret < 0) { + pr_err("Xen failed to enable clock %i. Error: %i\n", + i, ret); + goto out; + } + } + + ret = 0; + +out: + of_node_put(xen_node); + return ret; +} +late_initcall(xen_arm_register_clks); /* empty stubs */ void xen_arch_pre_suspend(void) { }