From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758873AbcLSNJp (ORCPT ); Mon, 19 Dec 2016 08:09:45 -0500 Received: from lelnx194.ext.ti.com ([198.47.27.80]:64730 "EHLO lelnx194.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752073AbcLSNJm (ORCPT ); Mon, 19 Dec 2016 08:09:42 -0500 Subject: Re: [PATCH] drm: tilcdc: simplify the recovery from sync lost error on rev1 To: Bartosz Golaszewski , Tomi Valkeinen , David Airlie , Kevin Hilman , Michael Turquette , Sekhar Nori References: <1481641656-25227-1-git-send-email-bgolaszewski@baylibre.com> CC: LKML , linux-drm , Peter Ujfalusi , arm-soc From: Jyri Sarha Message-ID: <590211f1-8e31-cecc-8dd2-f7e2976b81d1@ti.com> Date: Mon, 19 Dec 2016 15:09:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <1481641656-25227-1-git-send-email-bgolaszewski@baylibre.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org One comment bellow. On 12/13/16 17:07, Bartosz Golaszewski wrote: > Revision 2 of LCDC suffers from an issue where a SYNC_LOST error > caused by limited memory bandwidth may leave the picture shifted a > couple pixels to the right. > > This issue has not been observed on revision 1, while the recovery > mechanism introduces a different issue, where the END_OF_FRAME > interrupt doesn't fire while drm is waiting for vblanks. > > On rev1: recover from sync lost errors by simply clearing the > RASTER_ENABLE bit in the RASTER_CTRL register and re-enabling it > again as is suggested by the datasheet. > > Signed-off-by: Bartosz Golaszewski > --- > drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c > index 9942b05..70e57a7 100644 > --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c > +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c > @@ -921,17 +921,23 @@ irqreturn_t tilcdc_crtc_irq(struct drm_crtc *crtc) > dev_err_ratelimited(dev->dev, "%s(0x%08x): Sync lost", > __func__, stat); > tilcdc_crtc->frame_intact = false; > - if (tilcdc_crtc->sync_lost_count++ > > - SYNC_LOST_COUNT_LIMIT) { > - dev_err(dev->dev, "%s(0x%08x): Sync lost flood detected, recovering", __func__, stat); > - queue_work(system_wq, &tilcdc_crtc->recover_work); > - if (priv->rev == 1) > - tilcdc_clear(dev, LCDC_RASTER_CTRL_REG, > - LCDC_V1_SYNC_LOST_INT_ENA); > - else > + if (priv->rev == 1) { I would add here: + if ((tilcdc_read(dev, LCDC_RASTER_CTRL_REG) & + LCDC_RASTER_ENABLE)) { > + tilcdc_clear(dev, > + LCDC_RASTER_CTRL_REG, LCDC_RASTER_ENABLE); > + tilcdc_set(dev, > + LCDC_RASTER_CTRL_REG, LCDC_RASTER_ENABLE); + } Just in case the interrupt is for some reason handled right after the crtc is disabled. With this addition I could send a pull request for this fix still today, if you agree with the change. > + } else { > + if (tilcdc_crtc->sync_lost_count++ > > + SYNC_LOST_COUNT_LIMIT) { > + dev_err(dev->dev, > + "%s(0x%08x): Sync lost flood detected, recovering", > + __func__, stat); > + queue_work(system_wq, > + &tilcdc_crtc->recover_work); > tilcdc_write(dev, LCDC_INT_ENABLE_CLR_REG, > LCDC_SYNC_LOST); > - tilcdc_crtc->sync_lost_count = 0; > + tilcdc_crtc->sync_lost_count = 0; > + } > } > } > >