From patchwork Wed Aug 28 00:21:20 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Stone X-Patchwork-Id: 11117621 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C83F714DE for ; Wed, 28 Aug 2019 00:21:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97D942173E for ; Wed, 28 Aug 2019 00:21:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726077AbfH1AV3 (ORCPT ); Tue, 27 Aug 2019 20:21:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55142 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726044AbfH1AV3 (ORCPT ); Tue, 27 Aug 2019 20:21:29 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A269A307BCC7; Wed, 28 Aug 2019 00:21:28 +0000 (UTC) Received: from masetto.com (ovpn-116-56.phx2.redhat.com [10.3.116.56]) by smtp.corp.redhat.com (Postfix) with ESMTP id C3C7119D7A; Wed, 28 Aug 2019 00:21:25 +0000 (UTC) From: Al Stone To: linux-acpi@vger.kernel.org Cc: Al Stone , linux-kernel@vger.kernel.org Subject: [PATCH v3] ACPI / CPPC: do not require the _PSD method when using CPPC Date: Tue, 27 Aug 2019 18:21:20 -0600 Message-Id: <20190828002120.13669-1-ahs3@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 28 Aug 2019 00:21:28 +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 is 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 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. v3: -- bodged the simplification in v2; simplified it properly this time -- verified all error statuses are handled v2: -- verified simple check for AE_NOT_FOUND was sufficient -- simplified return status check per Rafael's suggestion Signed-off-by: Al Stone --- drivers/acpi/cppc_acpi.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 15f103d7532b..3b2525908dd8 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -365,8 +365,10 @@ 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); + status = acpi_evaluate_object_typed(handle, "_PSD", NULL, + &buffer, ACPI_TYPE_PACKAGE); + if (status == AE_NOT_FOUND) /* _PSD is optional */ + return 0; if (ACPI_FAILURE(status)) return -ENODEV;