Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751520AbdILKpG (ORCPT ); Tue, 12 Sep 2017 06:45:06 -0400 Received: from lelnx194.ext.ti.com ([198.47.27.80]:52438 "EHLO lelnx194.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751451AbdILKpC (ORCPT ); Tue, 12 Sep 2017 06:45:02 -0400 From: Peter Ujfalusi To: , CC: , , , , Subject: [PATCH 3/5] dmaengine: Support for querying maximum trasnfer length (of an SG element) Date: Tue, 12 Sep 2017 13:44:22 +0300 Message-ID: <20170912104424.18495-4-peter.ujfalusi@ti.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170912104424.18495-1-peter.ujfalusi@ti.com> References: <20170912104424.18495-1-peter.ujfalusi@ti.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v8CAjAJr015425 Content-Length: 2483 Lines: 63 Certain DMA engines have limitation on the maximum size of a transfer they can support. This size limitation is per SG element or for period length in cyclic transfers. In TI's eDMA and sDMA this limitation is not really a length limit, but it is the number of bursts that we can support in one transfer. With this callback the DMA drivers can provide hints to clients on how they should set up their buffers (sglist, cyclic buffer). Without this the clients must have open coded workarounds in place for each and every DMA engine they might be interfacing with to have correct length for the transfers. Signed-off-by: Peter Ujfalusi --- include/linux/dmaengine.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index 8319101170fc..739824b94c1b 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -705,6 +705,9 @@ struct dma_filter { * @device_prep_dma_imm_data: DMA's 8 byte immediate data to the dst address * @device_config: Pushes a new configuration to a channel, return 0 or an error * code + * @device_get_max_len: Get the maximum supported length in bytes of a slave + * transfer based on the set dma_slave_config. The length limitation + * applies to each SG element's length. * @device_pause: Pauses any transfer happening on a channel. Returns * 0 or an error code * @device_resume: Resumes any transfer on a channel previously @@ -792,6 +795,8 @@ struct dma_device { int (*device_config)(struct dma_chan *chan, struct dma_slave_config *config); + u32 (*device_get_max_len)(struct dma_chan *chan, + enum dma_transfer_direction dir); int (*device_pause)(struct dma_chan *chan); int (*device_resume)(struct dma_chan *chan); int (*device_terminate_all)(struct dma_chan *chan); @@ -812,6 +817,15 @@ static inline int dmaengine_slave_config(struct dma_chan *chan, return -ENOSYS; } +static inline u32 dmaengine_slave_get_max_len(struct dma_chan *chan, + enum dma_transfer_direction dir) +{ + if (chan->device->device_get_max_len) + return chan->device->device_get_max_len(chan, dir); + + return 0; +} + static inline bool is_slave_direction(enum dma_transfer_direction direction) { return (direction == DMA_MEM_TO_DEV) || (direction == DMA_DEV_TO_MEM); -- 2.14.1 Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki