From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934056AbaGOVjT (ORCPT ); Tue, 15 Jul 2014 17:39:19 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55007 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964826AbaGOVjA (ORCPT ); Tue, 15 Jul 2014 17:39:00 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , Jani Nikula , Kamal Mostafa Subject: [PATCH 3.13 143/198] drm/i915: Avoid div-by-zero when pixel_multiplier is zero Date: Tue, 15 Jul 2014 14:30:13 -0700 Message-Id: <1405459868-15089-144-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1405459868-15089-1-git-send-email-kamal@canonical.com> References: <1405459868-15089-1-git-send-email-kamal@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.5 -stable review patch. If anyone has any objections, please let me know. ------------------ From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= commit 2b85886a5457f5c5dbcd32edbd4e6bba0f4e8678 upstream. On certain platforms pixel_multiplier is read out in .get_pipe_config(), but it also gets used to calculate the pixel clock in intel_sdvo_get_config(). If the pipe is disable but some SDVO outputs are active, we may end up dividing by zero in intel_sdvo_get_config(). To avoid the problem simply check for zero pixel_multiplier and skip the division. Another attempt at fixing this involved populating pixel_multiplier to 1 even for disabled pipes, but that triggered a WARN because SDVO_CMD_GET_CLOCK_RATE_MULT command failed and thus encoder_pixel_multiplier was left at zero and didn't match pipe_config->pixel_multiplier. The "divide by pixel_multiplier" operation got introduced here: commit 18442d08786472c63a0a80c27f92b033dffc26de Author: Ville Syrjälä Date: Fri Sep 13 16:00:08 2013 +0300 drm/i915: Fix port_clock and adjusted_mode.clock readout all over and it has caused a regression on certain machines since they would hit the div-by-zero during resume. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76520 Tested-by: Tim Richardson Reviewed-by: Daniel Vetter Signed-off-by: Ville Syrjälä Signed-off-by: Jani Nikula Signed-off-by: Kamal Mostafa --- drivers/gpu/drm/i915/intel_sdvo.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c index a583e8f..9528239 100644 --- a/drivers/gpu/drm/i915/intel_sdvo.c +++ b/drivers/gpu/drm/i915/intel_sdvo.c @@ -1364,7 +1364,9 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder, >> SDVO_PORT_MULTIPLY_SHIFT) + 1; } - dotclock = pipe_config->port_clock / pipe_config->pixel_multiplier; + dotclock = pipe_config->port_clock; + if (pipe_config->pixel_multiplier) + dotclock /= pipe_config->pixel_multiplier; if (HAS_PCH_SPLIT(dev)) ironlake_check_encoder_dotclock(pipe_config, dotclock); -- 1.9.1