From patchwork Thu Apr 2 15:29:46 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lucas Stach X-Patchwork-Id: 6149381 Return-Path: X-Original-To: patchwork-dri-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id BDD31C058F for ; Thu, 2 Apr 2015 15:31:32 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id D68D8203B4 for ; Thu, 2 Apr 2015 15:31:31 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id E5905203AC for ; Thu, 2 Apr 2015 15:31:30 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 438EC6EA8B; Thu, 2 Apr 2015 08:31:04 -0700 (PDT) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [92.198.50.35]) by gabe.freedesktop.org (Postfix) with ESMTP id 83C6C6EA49 for ; Thu, 2 Apr 2015 08:30:58 -0700 (PDT) Received: from dude.hi.4.pengutronix.de ([10.1.0.7] helo=dude.pengutronix.de.) by metis.ext.pengutronix.de with esmtp (Exim 4.72) (envelope-from ) id 1Ydh57-0005OD-Qu; Thu, 02 Apr 2015 17:30:57 +0200 From: Lucas Stach To: dri-devel@lists.freedesktop.org Subject: [PATCH RFC 044/111] staging: etnaviv: fix DMA API usage Date: Thu, 2 Apr 2015 17:29:46 +0200 Message-Id: <1427988653-754-45-git-send-email-l.stach@pengutronix.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1427988653-754-1-git-send-email-l.stach@pengutronix.de> References: <1427988653-754-1-git-send-email-l.stach@pengutronix.de> X-SA-Exim-Connect-IP: 10.1.0.7 X-SA-Exim-Mail-From: l.stach@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: dri-devel@lists.freedesktop.org Cc: Russell King , kernel@pengutronix.de X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Russell King We test for write-combine and non-cacheable mappings before calling the DMA API. This is werid, because non-cacheable mappings are DMA coherent by definition, whereas cacheable mappings need cache maintanence provided by the DMA API. This seems to be a typo: ETNA_BO_CACHED should be used rather than ETNA_BO_UNCACHED. Moreover, add a comment to the dma_unmap_sg() site so to remind people about the data-corrupting implications of this call if it is abused (as can happen with the etnaviv DRM code structure as it currently stands with long-term mapping of the buffer.) Signed-off-by: Russell King --- drivers/staging/etnaviv/etnaviv_gem.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/drivers/staging/etnaviv/etnaviv_gem.c b/drivers/staging/etnaviv/etnaviv_gem.c index e508d64aa2d3..034ff732bdf4 100644 --- a/drivers/staging/etnaviv/etnaviv_gem.c +++ b/drivers/staging/etnaviv/etnaviv_gem.c @@ -48,7 +48,7 @@ static int etnaviv_gem_shmem_get_pages(struct etnaviv_gem_object *etnaviv_obj) /* For non-cached buffers, ensure the new pages are clean * because display controller, GPU, etc. are not coherent: */ - if (etnaviv_obj->flags & (ETNA_BO_WC|ETNA_BO_UNCACHED)) + if (etnaviv_obj->flags & (ETNA_BO_WC|ETNA_BO_CACHED)) dma_map_sg(dev->dev, etnaviv_obj->sgt->sgl, etnaviv_obj->sgt->nents, DMA_BIDIRECTIONAL); @@ -60,10 +60,22 @@ static void put_pages(struct etnaviv_gem_object *etnaviv_obj) if (etnaviv_obj->pages) { struct drm_device *dev = etnaviv_obj->base.dev; - /* For non-cached buffers, ensure the new pages are clean + /* + * For non-cached buffers, ensure the new pages are clean * because display controller, GPU, etc. are not coherent: + * + * WARNING: The DMA API does not support concurrent CPU + * and device access to the memory area. With BIDIRECTIONAL, + * we will clean the cache lines which overlap the region, + * and invalidate all cache lines (partially) contained in + * the region. + * + * If you have dirty data in the overlapping cache lines, + * that will corrupt the GPU-written data. If you have + * written into the remainder of the region, this can + * discard those writes. */ - if (etnaviv_obj->flags & (ETNA_BO_WC|ETNA_BO_UNCACHED)) + if (etnaviv_obj->flags & (ETNA_BO_WC|ETNA_BO_CACHED)) dma_unmap_sg(dev->dev, etnaviv_obj->sgt->sgl, etnaviv_obj->sgt->nents, DMA_BIDIRECTIONAL);