Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752412AbbENHQt (ORCPT ); Thu, 14 May 2015 03:16:49 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:35468 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751043AbbENHQr (ORCPT ); Thu, 14 May 2015 03:16:47 -0400 From: Thomas Gummerer To: Matt Roper Cc: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, David Airlie , Jani Nikula , Daniel Vetter , jan@gondor.com, Tvrtko Ursulin , Michael Leuchtenburg , Thomas Gummerer Subject: [PATCH v2] drm/i915: fix screen flickering Date: Thu, 14 May 2015 09:16:39 +0200 Message-Id: <1431587799-5399-1-git-send-email-t.gummerer@gmail.com> X-Mailer: git-send-email 2.4.0.184.g8e1974e In-Reply-To: <20150514032118.GD25648@intel.com> References: <20150514032118.GD25648@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2933 Lines: 81 Commit c9f038a1a592 ("drm/i915: Don't assume primary & cursor are always on for wm calculation (v4)") fixes a null pointer dereference. Setting the primary and cursor panes to false in ilk_compute_wm_parameters to false does however give the following errors in the kernel log and causes the screen to flicker. [ 101.133716] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* uncleared fifo underrun on pipe A [ 101.133725] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun Always setting the panes to enabled fixes this error. Helped-by: Matt Roper Signed-off-by: Thomas Gummerer --- > Sorry, I missed your patch when you first sent it. That type of fix > looks like an okay workaround while we do a more in-depth rework of the > watermark system. However I think your patch could cause a crash if we > disable the primary plane via the universal plane interface; if we do > that, p->pri.bytes_per_pixel is set to 0, but since we're now pretending > the primary plane is always enabled, ilk_wm_fbc() can eventually get > called and use that 0 in the denominator of a division operation. > > If you just squash the following change into your patch, I think it should be > safe: > [...] Thank you very much for the suggestion, here is an updated version of the patch. drivers/gpu/drm/i915/intel_pm.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c index fa4ccb3..555b896 100644 --- a/drivers/gpu/drm/i915/intel_pm.c +++ b/drivers/gpu/drm/i915/intel_pm.c @@ -2045,22 +2045,20 @@ static void ilk_compute_wm_parameters(struct drm_crtc *crtc, p->pipe_htotal = intel_crtc->config->base.adjusted_mode.crtc_htotal; p->pixel_rate = ilk_pipe_pixel_rate(dev, crtc); - if (crtc->primary->state->fb) { - p->pri.enabled = true; + if (crtc->primary->state->fb) p->pri.bytes_per_pixel = crtc->primary->state->fb->bits_per_pixel / 8; - } else { - p->pri.enabled = false; - p->pri.bytes_per_pixel = 0; - } + else + p->pri.bytes_per_pixel = 4; + + p->cur.bytes_per_pixel = 4; + /* + * TODO: for now, assume primary and cursor planes are always enabled. + * Setting them to false makes the screen flicker. + */ + p->pri.enabled = true; + p->cur.enabled = true; - if (crtc->cursor->state->fb) { - p->cur.enabled = true; - p->cur.bytes_per_pixel = 4; - } else { - p->cur.enabled = false; - p->cur.bytes_per_pixel = 0; - } p->pri.horiz_pixels = intel_crtc->config->pipe_src_w; p->cur.horiz_pixels = intel_crtc->base.cursor->state->crtc_w; -- 2.4.0.184.g8e1974e -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/