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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0DFE3C64EC4 for ; Fri, 10 Mar 2023 17:55:53 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9964F10E316; Fri, 10 Mar 2023 17:48:13 +0000 (UTC) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by gabe.freedesktop.org (Postfix) with ESMTPS id D0D0710E30D; Fri, 10 Mar 2023 17:48:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1678470490; x=1710006490; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=bee2h7Uihe+QYwTZwZ+fnOq+GIrmw0Sej7yiPuEmRfI=; b=DEQdOWDT5t9xqT/oB8lzYNTu9PGIDrFNRP2NnBtDjpgKx/kl3wxbq8vt RoRfguR/+GHquA3WIkrybjNzk9E/c+CZjLESrWl2WL9kEaAxsGkYKJ0bd 7iMI3e+MgZwpFasD9xL9r1ALS4AN+0G44cNj5EZL8A8YwYuBKowhQcX7l C59NDdN3tlzyzuThOsuYffqZNGRWipxeiSeLAdvErcNooTdQMuuEh3Hsn ygui05fGZ/So5y65K+LCBoN1aBKr48pFJ0ab4UE31s1PZ6pPI6pS00Q6c h4B2nmEbtBapzNRRO3FsSYu048vyi2eY6hIOsYJDRv0WVaCiuMeC3GhuC A==; X-IronPort-AV: E=McAfee;i="6500,9779,10645"; a="401648389" X-IronPort-AV: E=Sophos;i="5.98,250,1673942400"; d="scan'208";a="401648389" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2023 09:48:10 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10645"; a="766910021" X-IronPort-AV: E=Sophos;i="5.98,250,1673942400"; d="scan'208";a="766910021" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.70]) by FMSMGA003.fm.intel.com with SMTP; 10 Mar 2023 09:48:05 -0800 Received: by stinkbox (sSMTP sendmail emulation); Fri, 10 Mar 2023 19:48:04 +0200 Date: Fri, 10 Mar 2023 19:48:04 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Hamza Mahfooz Subject: Re: [PATCH] drm/amd/display: use a more accurate check in dm_helpers_dp_read_dpcd() Message-ID: References: <20230309213027.256243-1-hamza.mahfooz@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230309213027.256243-1-hamza.mahfooz@amd.com> X-Patchwork-Hint: comment X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ian Chen , Leo Li , Qingqing Zhuo , "Pan, Xinhui" , Rodrigo Siqueira , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Wayne Lin , Alex Deucher , Christian =?iso-8859-1?Q?K=F6nig?= , Sung Joon Kim Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On Thu, Mar 09, 2023 at 04:30:27PM -0500, Hamza Mahfooz wrote: > We should be checking if drm_dp_dpcd_read() returns the size that we are > asking it to read instead of just checking if it is greater than zero. > Also, we should WARN_ON() here since this condition is only ever met, if > there is an issue worth investigating. So, compare the return value of > drm_dp_dpcd_read() to size and WARN_ON() if they aren't equal. > > Signed-off-by: Hamza Mahfooz > --- > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c > index 8d598b322e5b..ed2ed7b1d869 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c > @@ -511,8 +511,8 @@ bool dm_helpers_dp_read_dpcd( > return false; > } > > - return drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address, > - data, size) > 0; > + return !WARN_ON(drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address, > + data, size) != size); Just FYI there are devices out there that violate the DP spec and reads from specific DPCD registers simply fail instead of returning the expected 0. > } > > bool dm_helpers_dp_write_dpcd( > -- > 2.39.2 -- Ville Syrjälä Intel 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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C291C6FD1C for ; Fri, 10 Mar 2023 17:49:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230132AbjCJRs6 (ORCPT ); Fri, 10 Mar 2023 12:48:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231314AbjCJRsw (ORCPT ); Fri, 10 Mar 2023 12:48:52 -0500 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1CF011ACBA for ; Fri, 10 Mar 2023 09:48:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1678470506; x=1710006506; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=bee2h7Uihe+QYwTZwZ+fnOq+GIrmw0Sej7yiPuEmRfI=; b=Goo01+efOzv+lyElcZDDrYd0LAEbF0grht/s9oBsVB9uZI1+wdHt5xqT 2O0V388RPxtwC+UmjZLm5nPwwmSB0+PABABdy0avUzWmaukb9xqLgiSFx VeLp9vzNur3iGOfnOEwb2u5F8JCfB7qZpC/TYfpCSuJPB7wgnVlueCHgy PE90Lg7OBL6X9DCk6WTJEpsyrklUsigrIpy+5Al2dNMiZbLAZsrrd7lOc 9T4FiZa71oo/O3oXg78r6LfP9G5a5Z2+8FYziToyxZtChEoRigE7r57Vf C7r+k8IIlXy3GA1nv0lrkv3VCmT0cR1IWKYTodatSub0t923D5DFtuqQc Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10645"; a="401648388" X-IronPort-AV: E=Sophos;i="5.98,250,1673942400"; d="scan'208";a="401648388" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2023 09:48:10 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10645"; a="766910021" X-IronPort-AV: E=Sophos;i="5.98,250,1673942400"; d="scan'208";a="766910021" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.70]) by FMSMGA003.fm.intel.com with SMTP; 10 Mar 2023 09:48:05 -0800 Received: by stinkbox (sSMTP sendmail emulation); Fri, 10 Mar 2023 19:48:04 +0200 Date: Fri, 10 Mar 2023 19:48:04 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Hamza Mahfooz Cc: amd-gfx@lists.freedesktop.org, Ian Chen , Leo Li , Qingqing Zhuo , "Pan, Xinhui" , Rodrigo Siqueira , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Wayne Lin , Alex Deucher , Christian =?iso-8859-1?Q?K=F6nig?= , Sung Joon Kim Subject: Re: [PATCH] drm/amd/display: use a more accurate check in dm_helpers_dp_read_dpcd() Message-ID: References: <20230309213027.256243-1-hamza.mahfooz@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230309213027.256243-1-hamza.mahfooz@amd.com> X-Patchwork-Hint: comment Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 09, 2023 at 04:30:27PM -0500, Hamza Mahfooz wrote: > We should be checking if drm_dp_dpcd_read() returns the size that we are > asking it to read instead of just checking if it is greater than zero. > Also, we should WARN_ON() here since this condition is only ever met, if > there is an issue worth investigating. So, compare the return value of > drm_dp_dpcd_read() to size and WARN_ON() if they aren't equal. > > Signed-off-by: Hamza Mahfooz > --- > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c > index 8d598b322e5b..ed2ed7b1d869 100644 > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c > @@ -511,8 +511,8 @@ bool dm_helpers_dp_read_dpcd( > return false; > } > > - return drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address, > - data, size) > 0; > + return !WARN_ON(drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address, > + data, size) != size); Just FYI there are devices out there that violate the DP spec and reads from specific DPCD registers simply fail instead of returning the expected 0. > } > > bool dm_helpers_dp_write_dpcd( > -- > 2.39.2 -- Ville Syrjälä Intel