From patchwork Tue Oct 5 15:00:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 12536991 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AB1B1C433EF for ; Tue, 5 Oct 2021 15:00:59 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 75EDC61381 for ; Tue, 5 Oct 2021 15:00:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 75EDC61381 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7B4856E41A; Tue, 5 Oct 2021 15:00:53 +0000 (UTC) Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by gabe.freedesktop.org (Postfix) with ESMTPS id 5BABA6E41B; Tue, 5 Oct 2021 15:00:52 +0000 (UTC) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1633446050; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YfV+dFFWxaAmjKgGZbxhOlXmxOzC0zReiVvOe/Up0ZY=; b=LhqNlRejgIsZ0umEZC5dzXBYp7foR7IDyEjWbDBSvSM4fpbSWAJQdBhMjN+tWYQT0Ptpz3 AzN6tNOWK+eYni6Emxvi6/QU+ectgHwUdGZqb2Zpa3n1sf64oEaRWXLpjdutTNpvSXLVAX Ach6pfdu7rFm3LdbVAWf6rwj1ZBX9tUkSnr+j0dK+X3fkj5OHmx/6mlwfNmm9NJqBQceSR H+YvPOdTEAEH2p78qWz633OwtDVpXjyssPPJrClCTxAxYO0u4BdxFEFIkuC/E5e2a6DdVP RjLXqfhyCXX5VeZyvz8JoZc+gjOiIrPujT9jJU8HiRe0UtowhYpiDfdcxfRLVg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1633446050; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YfV+dFFWxaAmjKgGZbxhOlXmxOzC0zReiVvOe/Up0ZY=; b=6xtLiZxyUVa+gFriBtoBzcc1aIwRCh7S1JLbgppgkSu91JpaDRM0sqXrv59XTVOAz3mnQ5 t+owGr9L12L7VqDw== To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , Thomas Gleixner , Mike Galbraith , Sebastian Andrzej Siewior Subject: [PATCH 2/8] drm/i915: Don't disable interrupts on PREEMPT_RT during atomic updates Date: Tue, 5 Oct 2021 17:00:40 +0200 Message-Id: <20211005150046.1000285-3-bigeasy@linutronix.de> In-Reply-To: <20211005150046.1000285-1-bigeasy@linutronix.de> References: <20211005150046.1000285-1-bigeasy@linutronix.de> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Mike Galbraith Commit 8d7849db3eab7 ("drm/i915: Make sprite updates atomic") started disabling interrupts across atomic updates. This breaks on PREEMPT_RT because within this section the code attempt to acquire spinlock_t locks which are sleeping locks on PREEMPT_RT. According to the comment the interrupts are disabled to avoid random delays and not required for protection or synchronisation. If this needs to happen with disabled interrupts on PREEMPT_RT, and the whole section is restricted to register access then all sleeping locks need to be acquired before interrupts are disabled and some function maybe moved after enabling interrupts again. This includes: - prepare_to_wait() + finish_wait() due its wake queue. - drm_crtc_vblank_put() -> vblank_disable_fn() drm_device::vbl_lock. - skl_pfit_enable(), intel_update_plane(), vlv_atomic_update_fifo() and maybe others due to intel_uncore::lock - drm_crtc_arm_vblank_event() due to drm_device::event_lock and drm_device::vblank_time_lock. Don't disable interrupts on PREEMPT_RT during atomic updates. [bigeasy: drop local locks, commit message] Signed-off-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior --- drivers/gpu/drm/i915/display/intel_crtc.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c b/drivers/gpu/drm/i915/display/intel_crtc.c index 254e67141a776..7a39029b083f4 100644 --- a/drivers/gpu/drm/i915/display/intel_crtc.c +++ b/drivers/gpu/drm/i915/display/intel_crtc.c @@ -425,7 +425,8 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state) */ intel_psr_wait_for_idle(new_crtc_state); - local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); crtc->debug.min_vbl = min; crtc->debug.max_vbl = max; @@ -450,11 +451,13 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state) break; } - local_irq_enable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_enable(); timeout = schedule_timeout(timeout); - local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); } finish_wait(wq, &wait); @@ -487,7 +490,8 @@ void intel_pipe_update_start(const struct intel_crtc_state *new_crtc_state) return; irq_disable: - local_irq_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_disable(); } #if IS_ENABLED(CONFIG_DRM_I915_DEBUG_VBLANK_EVADE) @@ -566,7 +570,8 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state) new_crtc_state->uapi.event = NULL; } - local_irq_enable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_irq_enable(); /* Send VRR Push to terminate Vblank */ intel_vrr_send_push(new_crtc_state);