From patchwork Wed Apr 15 15:38:45 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Previte X-Patchwork-Id: 6221531 Return-Path: X-Original-To: patchwork-dri-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 1D430BF4A6 for ; Wed, 15 Apr 2015 15:39:18 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 406A720328 for ; Wed, 15 Apr 2015 15:39:17 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id 42936202FE for ; Wed, 15 Apr 2015 15:39:16 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9A5356E882; Wed, 15 Apr 2015 08:39:15 -0700 (PDT) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by gabe.freedesktop.org (Postfix) with ESMTP id A8D776E882; Wed, 15 Apr 2015 08:39:13 -0700 (PDT) Received: by pabsx10 with SMTP id sx10so54803151pab.3; Wed, 15 Apr 2015 08:39:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=fhcB2zGo7Z3BKHL78C0u84rNXVoNqcuCS56OSBip/XY=; b=OtOAssJqstOrZDQaFseWdWqkXfvpPdsH9aXwsQp7PlYJ4DiSJZ+q+H6X6QCnc7Ho++ 6jV7W3SK2cAl71DUhFsJhcNA4pPFUUN25NU6lLQDC7MQWjXmdrL7HSAbkbhhwdjamJqz YNa/UJtNrrUmtJBe/lh9bm4YrAVbg4/I8jx6UhOGUvciC9E/1g3X57BQ37jo0i1wd2h0 n/yDsxX6vYoMV3SlSW4EpuZJE132un8eDM0YAbzwrYjptOfmatbbO57KsGUct10bC0nh VMMXkUcho1VWB9vfPzNZ6yejRVCW8+HCmQSrUHSmwl+iGFKRGpIQGpFtuWGnwNtRumg0 qMhA== X-Received: by 10.66.124.164 with SMTP id mj4mr48328614pab.83.1429112353517; Wed, 15 Apr 2015 08:39:13 -0700 (PDT) Received: from localhost.localdomain (ip70-162-72-208.ph.ph.cox.net. [70.162.72.208]) by mx.google.com with ESMTPSA id su5sm4484999pbc.38.2015.04.15.08.39.12 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 15 Apr 2015 08:39:12 -0700 (PDT) From: Todd Previte To: intel-gfx@lists.freedesktop.org Subject: [PATCH 08/10] drm: Fix for DP CTS test 4.2.2.5 - I2C DEFER handling Date: Wed, 15 Apr 2015 08:38:45 -0700 Message-Id: <1429112327-7695-9-git-send-email-tprevite@gmail.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1429112327-7695-1-git-send-email-tprevite@gmail.com> References: <1429112327-7695-1-git-send-email-tprevite@gmail.com> Cc: dri-devel@lists.freedesktop.org X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Spam-Status: No, score=-4.1 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_MED, T_DKIM_INVALID, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP For test 4.2.2.5 to pass per the Link CTS Core 1.2 rev1.1 spec, the source device must attempt at least 7 times to read the EDID when it receives an I2C defer. The normal DRM code makes only 7 retries, regardless of whether or not the response is a native defer or an I2C defer. Test 4.2.2.5 fails since there are native defers interspersed with the I2C defers which results in less than 7 EDID read attempts. The solution is to add the numer of defers to the retry counter when an I2C DEFER is returned such that another read attempt will be made. This situation should normally only occur in compliance testing, however, as a worse case real-world scenario, it would result in 13 attempts ( 6 native defers, 7 I2C defers) for a single transaction to complete. The net result is a slightly slower response to an EDID read that shouldn't significantly impact overall performance. V2: - Added a check on the number of I2C Defers to limit the number of times that the retries variable will be decremented. This is to address review feedback regarding possible infinite loops from misbehaving sink devices. V3: - Fixed the limit value to 7 instead of 8 to get the correct retry count. - Combined the increment of the defer count into the if-statement V4: - Removed i915 tag from subject as the patch is not i915-specific V5: - Updated the for-loop to add the number of i2c defers to the retry counter such that the correct number of retry attempts will be made Signed-off-by: Todd Previte Cc: dri-devel@lists.freedesktop.org Reviewed-by: Paulo Zanoni --- drivers/gpu/drm/drm_dp_helper.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 71dcbc6..7f0356e 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -432,7 +432,7 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) */ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { - unsigned int retry; + unsigned int retry, defer_i2c; int ret; /* @@ -440,7 +440,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) * is required to retry at least seven times upon receiving AUX_DEFER * before giving up the AUX transaction. */ - for (retry = 0; retry < 7; retry++) { + for (retry = 0, defer_i2c = 0; retry < (7 + defer_i2c); retry++) { mutex_lock(&aux->hw_mutex); ret = aux->transfer(aux, msg); mutex_unlock(&aux->hw_mutex); @@ -499,7 +499,13 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) case DP_AUX_I2C_REPLY_DEFER: DRM_DEBUG_KMS("I2C defer\n"); + /* DP Compliance Test 4.2.2.5 Requirement: + * Must have at least 7 retries for I2C defers on the + * transaction to pass this test + */ aux->i2c_defer_count++; + if (defer_i2c < 7) + defer_i2c++; usleep_range(400, 500); continue;