From patchwork Mon Aug 5 17:03:38 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Stone X-Patchwork-Id: 11077619 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1EE3414E5 for ; Mon, 5 Aug 2019 17:03:51 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0AD5528956 for ; Mon, 5 Aug 2019 17:03:51 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F358C28961; Mon, 5 Aug 2019 17:03:50 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI 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 9E1E928956 for ; Mon, 5 Aug 2019 17:03:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728800AbfHERDu (ORCPT ); Mon, 5 Aug 2019 13:03:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48968 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727830AbfHERDu (ORCPT ); Mon, 5 Aug 2019 13:03:50 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 976D0369D3; Mon, 5 Aug 2019 17:03:49 +0000 (UTC) Received: from masetto.com (ovpn-117-160.phx2.redhat.com [10.3.117.160]) by smtp.corp.redhat.com (Postfix) with ESMTP id EF6CB5DA21; Mon, 5 Aug 2019 17:03:46 +0000 (UTC) From: Al Stone To: linux-acpi@vger.kernel.org Cc: Al Stone , linux-kernel@vger.kernel.org, "Rafael J . Wysocki" , Len Brown Subject: [PATCH] ACPI / CPPC: do not require the _PSD method when using CPPC Date: Mon, 5 Aug 2019 11:03:38 -0600 Message-Id: <20190805170338.29493-1-ahs3@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Mon, 05 Aug 2019 17:03:49 +0000 (UTC) Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP According to the ACPI 6.3 specification, the _PSD method is optional when using CPPC. The underlying assumption appears to be that each CPU can change frequency independently from all other CPUs; _PSD is provided to tell the OS that some processors can NOT do that. However, the acpi_get_psd() function returns -ENODEV if there is no _PSD method present, or an ACPI error status if an error occurs when evaluating _PSD, if present. This essentially makes _PSD mandatory when using CPPC, in violation of the specification, and only on Linux. This has forced some firmware writers to provide a dummy _PSD, even though it is irrelevant, but only because Linux requires it; other OSPMs follow the spec. We really do not want to have OS specific ACPI tables, though. So, correct acpi_get_psd() so that it does not return an error if there is no _PSD method present, but does return a failure when the method can not be executed properly. This allows _PSD to be optional as it should be. Signed-off-by: Al Stone Cc: Rafael J. Wysocki Cc: Len Brown Reviewed-by: Sudeep Holla < sudeep.holla@arm.com> --- drivers/acpi/cppc_acpi.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 15f103d7532b..e9ecfa13e997 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -365,10 +365,13 @@ static int acpi_get_psd(struct cpc_desc *cpc_ptr, acpi_handle handle) union acpi_object *psd = NULL; struct acpi_psd_package *pdomain; - status = acpi_evaluate_object_typed(handle, "_PSD", NULL, &buffer, - ACPI_TYPE_PACKAGE); - if (ACPI_FAILURE(status)) - return -ENODEV; + if (acpi_has_method(handle, "_PSD")) { + status = acpi_evaluate_object_typed(handle, "_PSD", NULL, + &buffer, ACPI_TYPE_PACKAGE); + if (ACPI_FAILURE(status)) + return -ENODEV; + } else + return 0; /* _PSD is optional */ psd = buffer.pointer; if (!psd || psd->package.count != 1) {