From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756728AbcLSOTv (ORCPT ); Mon, 19 Dec 2016 09:19:51 -0500 Received: from mail-it0-f48.google.com ([209.85.214.48]:37680 "EHLO mail-it0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755247AbcLSOTV (ORCPT ); Mon, 19 Dec 2016 09:19:21 -0500 MIME-Version: 1.0 In-Reply-To: <590211f1-8e31-cecc-8dd2-f7e2976b81d1@ti.com> References: <1481641656-25227-1-git-send-email-bgolaszewski@baylibre.com> <590211f1-8e31-cecc-8dd2-f7e2976b81d1@ti.com> From: Bartosz Golaszewski Date: Mon, 19 Dec 2016 15:19:20 +0100 Message-ID: Subject: Re: [PATCH] drm: tilcdc: simplify the recovery from sync lost error on rev1 To: Jyri Sarha Cc: Tomi Valkeinen , David Airlie , Kevin Hilman , Michael Turquette , Sekhar Nori , LKML , linux-drm , Peter Ujfalusi , arm-soc Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2016-12-19 14:09 GMT+01:00 Jyri Sarha : > 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. I'm not sure this can really happen, but it won't hurt either, so I'll send a v2. Thanks, Bartosz