From patchwork Fri May 11 12:11:47 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 10394123 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 3FB8B60170 for ; Fri, 11 May 2018 12:12:13 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 020B628E3E for ; Fri, 11 May 2018 12:12:13 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EB06A28E7B; Fri, 11 May 2018 12:12:12 +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=-5.2 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id A2A5B28E3E for ; Fri, 11 May 2018 12:12:12 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 041BF6F11D; Fri, 11 May 2018 12:12:12 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id 52D5D6F129 for ; Fri, 11 May 2018 12:12:09 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from haswell.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 11670231-1500050 for multiple; Fri, 11 May 2018 13:11:53 +0100 Received: by haswell.alporthouse.com (sSMTP sendmail emulation); Fri, 11 May 2018 13:11:52 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Fri, 11 May 2018 13:11:47 +0100 Message-Id: <20180511121147.31915-3-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180511121147.31915-1-chris@chris-wilson.co.uk> References: <20180511121147.31915-1-chris@chris-wilson.co.uk> MIME-Version: 1.0 X-Originating-IP: 78.156.65.138 X-Country: code=GB country="United Kingdom" ip=78.156.65.138 Subject: [Intel-gfx] [PATCH 3/3] drm/i915/execlists: Relax CSB force-mmio for VT-d X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Virus-Scanned: ClamAV using ClamSMTP The original switch to use CSB from the HWSP was plagued by the effort of read ordering on VT-d; we would read the WRITE pointer from the HWSP before it had completed writing the CSB contents. The mystery comes down to the lack of rmb() for correct ordering with respect to the writes from HW, and with that resolved we can remove the VT-d special casing. Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: Joonas Lahtinen Cc: Tvrtko Ursulin Cc: Michał Winiarski Cc: Michel Thierry Tested-by: Mika Kuoppala Reviewed-by: Mika Kuoppala --- drivers/gpu/drm/i915/intel_engine_cs.c | 8 -------- 1 file changed, 8 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c index 8303e05b0c7d..6bfd7e3ed152 100644 --- a/drivers/gpu/drm/i915/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/intel_engine_cs.c @@ -458,14 +458,6 @@ static void intel_engine_init_batch_pool(struct intel_engine_cs *engine) static bool csb_force_mmio(struct drm_i915_private *i915) { - /* - * IOMMU adds unpredictable latency causing the CSB write (from the - * GPU into the HWSP) to only be visible some time after the interrupt - * (missed breadcrumb syndrome). - */ - if (intel_vtd_active()) - return true; - /* Older GVT emulation depends upon intercepting CSB mmio */ if (intel_vgpu_active(i915) && !intel_vgpu_has_hwsp_emulation(i915)) return true;