From patchwork Sat Jul 29 21:08:54 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Pinchart X-Patchwork-Id: 9870149 X-Patchwork-Delegate: geert@linux-m68k.org Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id C6E1760353 for ; Sat, 29 Jul 2017 21:08:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B9EB628557 for ; Sat, 29 Jul 2017 21:08:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AEC0228569; Sat, 29 Jul 2017 21:08:54 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3999B285AE for ; Sat, 29 Jul 2017 21:08:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751630AbdG2VIx (ORCPT ); Sat, 29 Jul 2017 17:08:53 -0400 Received: from galahad.ideasonboard.com ([185.26.127.97]:49545 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751634AbdG2VIv (ORCPT ); Sat, 29 Jul 2017 17:08:51 -0400 Received: from avalon.bb.dnainternet.fi (dfj612ybrt5fhg77mgycy-3.rev.dnainternet.fi [IPv6:2001:14ba:21f5:5b00:2e86:4862:ef6a:2804]) by galahad.ideasonboard.com (Postfix) with ESMTPSA id 53ADD208A0; Sat, 29 Jul 2017 23:07:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1501362476; bh=OJ1TWq/UZGexHO7DShfF7CDvKnrvgzwtGiJgu1PJY0g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p1OKlXlT2nEO2kW9zvZrVmW1Taw+LmzLozZXntEnGU/WMNu1rlc+KDGt+7RSM6taP smso9OzTUCMMDH30VxIopk1KxKUI8rOIfLt7kyzk8g47nsVpZqBxjUnuE6nunBHsjQ 8Pj195EnWbNVLcxbqmIAPcv9JzM94IybLKj2m6Y4= From: Laurent Pinchart To: dri-devel@lists.freedesktop.org Cc: linux-renesas-soc@vger.kernel.org, linux-media@vger.kernel.org, Kieran Bingham Subject: [PATCH v3 3/4] drm: rcar-du: Fix race condition when disabling planes at CRTC stop Date: Sun, 30 Jul 2017 00:08:54 +0300 Message-Id: <20170729210855.9187-4-laurent.pinchart+renesas@ideasonboard.com> X-Mailer: git-send-email 2.13.0 In-Reply-To: <20170729210855.9187-1-laurent.pinchart+renesas@ideasonboard.com> References: <20170729210855.9187-1-laurent.pinchart+renesas@ideasonboard.com> Sender: linux-renesas-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When stopping the CRTC the driver must disable all planes and wait for the change to take effect at the next vblank. Merely calling drm_crtc_wait_one_vblank() is not enough, as the function doesn't include any mechanism to handle the race with vblank interrupts. Replace the drm_crtc_wait_one_vblank() call with a manual mechanism that handles the vblank interrupt race. Signed-off-by: Laurent Pinchart Reviewed-by: Kieran Bingham --- drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 58 ++++++++++++++++++++++++++++++---- drivers/gpu/drm/rcar-du/rcar_du_crtc.h | 8 +++++ 2 files changed, 60 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c index 17fd1cd5212c..6e5bd0b92dfa 100644 --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c @@ -490,23 +490,51 @@ static void rcar_du_crtc_start(struct rcar_du_crtc *rcrtc) rcar_du_group_start_stop(rcrtc->group, true); } +static void rcar_du_crtc_disable_planes(struct rcar_du_crtc *rcrtc) +{ + struct rcar_du_device *rcdu = rcrtc->group->dev; + struct drm_crtc *crtc = &rcrtc->crtc; + u32 status; + + /* Make sure vblank interrupts are enabled. */ + drm_crtc_vblank_get(crtc); + + /* + * Disable planes and calculate how many vertical blanking interrupts we + * have to wait for. If a vertical blanking interrupt has been triggered + * but not processed yet, we don't know whether it occurred before or + * after the planes got disabled. We thus have to wait for two vblank + * interrupts in that case. + */ + spin_lock_irq(&rcrtc->vblank_lock); + rcar_du_group_write(rcrtc->group, rcrtc->index % 2 ? DS2PR : DS1PR, 0); + status = rcar_du_crtc_read(rcrtc, DSSR); + rcrtc->vblank_count = status & DSSR_VBK ? 2 : 1; + spin_unlock_irq(&rcrtc->vblank_lock); + + if (!wait_event_timeout(rcrtc->vblank_wait, rcrtc->vblank_count == 0, + msecs_to_jiffies(100))) + dev_warn(rcdu->dev, "vertical blanking timeout\n"); + + drm_crtc_vblank_put(crtc); +} + static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc) { struct drm_crtc *crtc = &rcrtc->crtc; /* * Disable all planes and wait for the change to take effect. This is - * required as the DSnPR registers are updated on vblank, and no vblank - * will occur once the CRTC is stopped. Disabling planes when starting - * the CRTC thus wouldn't be enough as it would start scanning out - * immediately from old frame buffers until the next vblank. + * required as the plane enable registers are updated on vblank, and no + * vblank will occur once the CRTC is stopped. Disabling planes when + * starting the CRTC thus wouldn't be enough as it would start scanning + * out immediately from old frame buffers until the next vblank. * * This increases the CRTC stop delay, especially when multiple CRTCs * are stopped in one operation as we now wait for one vblank per CRTC. * Whether this can be improved needs to be researched. */ - rcar_du_group_write(rcrtc->group, rcrtc->index % 2 ? DS2PR : DS1PR, 0); - drm_crtc_wait_one_vblank(crtc); + rcar_du_crtc_disable_planes(rcrtc); /* * Disable vertical blanking interrupt reporting. We first need to wait @@ -695,10 +723,26 @@ static irqreturn_t rcar_du_crtc_irq(int irq, void *arg) irqreturn_t ret = IRQ_NONE; u32 status; + spin_lock(&rcrtc->vblank_lock); + status = rcar_du_crtc_read(rcrtc, DSSR); rcar_du_crtc_write(rcrtc, DSRCR, status & DSRCR_MASK); if (status & DSSR_VBK) { + /* + * Wake up the vblank wait if the counter reaches 0. This must + * be protected by the vblank_lock to avoid races in + * rcar_du_crtc_disable_planes(). + */ + if (rcrtc->vblank_count) { + if (--rcrtc->vblank_count == 0) + wake_up(&rcrtc->vblank_wait); + } + } + + spin_unlock(&rcrtc->vblank_lock); + + if (status & DSSR_VBK) { drm_crtc_handle_vblank(&rcrtc->crtc); if (rcdu->info->gen < 3) @@ -756,6 +800,8 @@ int rcar_du_crtc_create(struct rcar_du_group *rgrp, unsigned int index) } init_waitqueue_head(&rcrtc->flip_wait); + init_waitqueue_head(&rcrtc->vblank_wait); + spin_lock_init(&rcrtc->vblank_lock); rcrtc->group = rgrp; rcrtc->mmio_offset = mmio_offsets[index]; diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h index 3cc376826592..065b91f5b1d9 100644 --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h @@ -15,6 +15,7 @@ #define __RCAR_DU_CRTC_H__ #include +#include #include #include @@ -33,6 +34,9 @@ struct rcar_du_vsp; * @initialized: whether the CRTC has been initialized and clocks enabled * @event: event to post when the pending page flip completes * @flip_wait: wait queue used to signal page flip completion + * @vblank_lock: protects vblank_wait and vblank_count + * @vblank_wait: wait queue used to signal vertical blanking + * @vblank_count: number of vertical blanking interrupts to wait for * @outputs: bitmask of the outputs (enum rcar_du_output) driven by this CRTC * @group: CRTC group this CRTC belongs to * @vsp: VSP feeding video to this CRTC @@ -50,6 +54,10 @@ struct rcar_du_crtc { struct drm_pending_vblank_event *event; wait_queue_head_t flip_wait; + spinlock_t vblank_lock; + wait_queue_head_t vblank_wait; + unsigned int vblank_count; + unsigned int outputs; struct rcar_du_group *group;