From patchwork Mon Aug 26 22:30:47 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Stone X-Patchwork-Id: 11115749 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 50AD2112C for ; Mon, 26 Aug 2019 22:30:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 37F212080C for ; Mon, 26 Aug 2019 22:30:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726441AbfHZWaz (ORCPT ); Mon, 26 Aug 2019 18:30:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39374 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726281AbfHZWaz (ORCPT ); Mon, 26 Aug 2019 18:30:55 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 33325300C22F; Mon, 26 Aug 2019 22:30:55 +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 3A9655C1B2; Mon, 26 Aug 2019 22:30:52 +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 v2] ACPI / CPPC: do not require the _PSD method when using CPPC Date: Mon, 26 Aug 2019 16:30:47 -0600 Message-Id: <20190826223047.13146-1-ahs3@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Mon, 26 Aug 2019 22:30:55 +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. v2: -- verified simple check for AE_NOT_FOUND was sufficient -- simplified return status check per Rafael's suggestion Signed-off-by: Al Stone Cc: Rafael J. Wysocki Cc: Len Brown --- drivers/acpi/cppc_acpi.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 15f103d7532b..7a946f1944ab 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -365,10 +365,12 @@ 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 (status == AE_NOT_FOUND) /* _PSD is optional */ + return 0; + } psd = buffer.pointer; if (!psd || psd->package.count != 1) {