From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4133C433FF for ; Mon, 5 Aug 2019 17:03:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A04682075B 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 Content-Transfer-Encoding: 8bit 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 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 --- 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) { -- 2.21.0