From patchwork Thu Jul 30 15:45:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11693347 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 57C3914B7 for ; Thu, 30 Jul 2020 15:45:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4893822CAF for ; Thu, 30 Jul 2020 15:45:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729953AbgG3Pp4 (ORCPT ); Thu, 30 Jul 2020 11:45:56 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:57322 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726275AbgG3Ppz (ORCPT ); Thu, 30 Jul 2020 11:45:55 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id DB0A1803202F; Thu, 30 Jul 2020 15:45:52 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CFlFm4HzIXgH; Thu, 30 Jul 2020 18:45:52 +0300 (MSK) From: Serge Semin To: Vinod Koul , Viresh Kumar , Andy Shevchenko , Rob Herring CC: Serge Semin , Serge Semin , Alexey Malahov , Pavel Parkhomenko , Peter Ujfalusi , Andy Shevchenko , , , Subject: [PATCH 1/5] dt-bindings: dma: dw: Add optional DMA-channels mask cell support Date: Thu, 30 Jul 2020 18:45:41 +0300 Message-ID: <20200730154545.3965-2-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> References: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org Each DW DMA controller channel can be synthesized with different parameters like maximum burst-length, multi-block support, maximum data width, etc. Most of these parameters determine the DW DMAC channels performance in its own aspect. On the other hand these parameters can be implicitly responsible for the channels performance degradation (for instance multi-block support is a very useful feature, but having it disabled during the DW DMAC synthesize will provide a more optimized core). Since DMA slave devices may have critical dependency on the DMA engine performance, let's provide a way for the slave devices to have the DMA-channels allocated from a pool of the channels, which according to the system engineer fulfill their performance requirements. The pool is determined by a mask optionally specified in the fifth DMA-cell of the DMA DT-property. If the fifth cell is omitted from the phandle arguments or the mask is zero, then the allocation will be performed from a set of all channels provided by the DMA controller. Signed-off-by: Serge Semin Reviewed-by: Rob Herring --- .../devicetree/bindings/dma/snps,dma-spear1340.yaml | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/Documentation/devicetree/bindings/dma/snps,dma-spear1340.yaml b/Documentation/devicetree/bindings/dma/snps,dma-spear1340.yaml index 20870f5c14dd..ef1d6879c158 100644 --- a/Documentation/devicetree/bindings/dma/snps,dma-spear1340.yaml +++ b/Documentation/devicetree/bindings/dma/snps,dma-spear1340.yaml @@ -18,12 +18,15 @@ properties: const: snps,dma-spear1340 "#dma-cells": - const: 3 + minimum: 3 + maximum: 4 description: | First cell is a phandle pointing to the DMA controller. Second one is the DMA request line number. Third cell is the memory master identifier for transfers on dynamically allocated channel. Fourth cell is the - peripheral master identifier for transfers on an allocated channel. + peripheral master identifier for transfers on an allocated channel. Fifth + cell is an optional mask of the DMA channels permitted to be allocated + for the corresponding client device. reg: maxItems: 1 From patchwork Thu Jul 30 15:45:42 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11693353 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1AA8314B7 for ; Thu, 30 Jul 2020 15:46:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C04020838 for ; Thu, 30 Jul 2020 15:46:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729975AbgG3Pp5 (ORCPT ); Thu, 30 Jul 2020 11:45:57 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:57362 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726581AbgG3Pp5 (ORCPT ); Thu, 30 Jul 2020 11:45:57 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id E541B8030866; Thu, 30 Jul 2020 15:45:54 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ubn64PjSapSu; Thu, 30 Jul 2020 18:45:53 +0300 (MSK) From: Serge Semin To: Vinod Koul , Viresh Kumar , Andy Shevchenko , Dan Williams CC: Serge Semin , Serge Semin , Alexey Malahov , Pavel Parkhomenko , Peter Ujfalusi , Andy Shevchenko , Rob Herring , , , Subject: [PATCH 2/5] dmaengine: dw: Activate FIFO-mode for memory peripherals only Date: Thu, 30 Jul 2020 18:45:42 +0300 Message-ID: <20200730154545.3965-3-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> References: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org CFGx.FIFO_MODE field controls a DMA-controller "FIFO readiness" criterion. In other words it determines when to start pushing data out of a DW DMAC channel FIFO to a destination peripheral or from a source peripheral to the DW DMAC channel FIFO. Currently FIFO-mode is set to one for all DW DMAC channels. It means they are tuned to flush data out of FIFO (to a memory peripheral or by accepting the burst transaction requests) when FIFO is at least half-full (except at the end of the block transfer, when FIFO-flush mode is activated) and are configured to get data to the FIFO when it's at least half-empty. Such configuration is a good choice when there is no slave device involved in the DMA transfers. In that case the number of bursts per block is less than when CFGx.FIFO_MODE = 0 and, hence, the bus utilization will improve. But the latency of DMA transfers may increase when CFGx.FIFO_MODE = 1, since DW DMAC will wait for the channel FIFO contents to be either half-full or half-empty depending on having the destination or the source transfers. Such latencies might be dangerous in case if the DMA transfers are expected to be performed from/to a slave device. Since normally peripheral devices keep data in internal FIFOs, any latency at some critical moment may cause one being overflown and consequently losing data. This especially concerns a case when either a peripheral device is relatively fast or the DW DMAC engine is relatively slow with respect to the incoming data pace. In order to solve problems, which might be caused by the latencies described above, let's enable the FIFO half-full/half-empty "FIFO readiness" criterion only for DMA transfers with no slave device involved. Thanks to the commit ???????????? ("dmaengine: dw: Initialize channel before each transfer") we can freely do that in the generic dw_dma_initialize_chan() method. Signed-off-by: Serge Semin Reviewed-by: Andy Shevchenko --- Note the DMA-engine repository git.infradead.org/users/vkoul/slave-dma.git isn't accessible. So I couldn't find out the Andy' commit hash to use it in the log. --- drivers/dma/dw/dw.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/dw/dw.c b/drivers/dma/dw/dw.c index 7a085b3c1854..d9810980920a 100644 --- a/drivers/dma/dw/dw.c +++ b/drivers/dma/dw/dw.c @@ -14,7 +14,7 @@ static void dw_dma_initialize_chan(struct dw_dma_chan *dwc) { struct dw_dma *dw = to_dw_dma(dwc->chan.device); - u32 cfghi = DWC_CFGH_FIFO_MODE; + u32 cfghi = is_slave_direction(dwc->direction) ? 0 : DWC_CFGH_FIFO_MODE; u32 cfglo = DWC_CFGL_CH_PRIOR(dwc->priority); bool hs_polarity = dwc->dws.hs_polarity; From patchwork Thu Jul 30 15:45:43 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11693357 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4C593138A for ; Thu, 30 Jul 2020 15:46:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F89F20838 for ; Thu, 30 Jul 2020 15:46:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730011AbgG3PqR (ORCPT ); Thu, 30 Jul 2020 11:46:17 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:57382 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729777AbgG3Pp5 (ORCPT ); Thu, 30 Jul 2020 11:45:57 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id F22EE8040A6A; Thu, 30 Jul 2020 15:45:54 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 79Cw5IwDZWQc; Thu, 30 Jul 2020 18:45:54 +0300 (MSK) From: Serge Semin To: Vinod Koul , Viresh Kumar , Andy Shevchenko , Dan Williams CC: Serge Semin , Serge Semin , Alexey Malahov , Pavel Parkhomenko , Peter Ujfalusi , Andy Shevchenko , Rob Herring , , , Subject: [PATCH 3/5] dmaengine: dw: Discard dlen from the dev-to-mem xfer width calculation Date: Thu, 30 Jul 2020 18:45:43 +0300 Message-ID: <20200730154545.3965-4-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> References: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org Indeed in case of the DMA_DEV_TO_MEM DMA transfers it's enough to take the destination memory address and the destination master data width into account to calculate the CTLx.DST_TR_WIDTH setting of the memory peripheral. According to the DW DMAC IP-core Databook (page 66, Example 5) at the and of a DMA transfer when the DMA-channel internal FIFO is left with data less than for a single destination burst transaction, the destination peripheral will enter the Single Transaction Region where the DW DMA controller can complete a block transfer to the destination using single transactions (non-burst transaction of CTLx.DST_TR_WIDTH bytes). If there is no enough data in the DMA-channel internal FIFO for even a single non-burst transaction of CTLx.DST_TR_WIDTH bytes, then the channel enters "FIFO flush mode". That mode is activated to empty the FIFO and flush the leftovers out to the memory peripheral. The flushing procedure is simple. The data is sent to the memory by means of a set of single transaction of CTLx.SRC_TR_WIDTH bytes. To sum up it's redundant to use the LLPs length to find out the CTLx.DST_TR_WIDTH parameter value, since each DMA transfer will be completed with the CTLx.SRC_TR_WIDTH bytes transaction if it is required. In this commit we remove the LLP entry length from the statement which calculates the memory peripheral DMA transaction width since it's redundant due to the feature described above. By doing so we'll improve the memory bus utilization and speed up the DMA-channel performance for DMA_DEV_TO_MEM DMA-transfers. Signed-off-by: Serge Semin Acked-by: Andy Shevchenko --- drivers/dma/dw/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c index 4700f2e87a62..3da0aea9fe25 100644 --- a/drivers/dma/dw/core.c +++ b/drivers/dma/dw/core.c @@ -723,7 +723,7 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl, lli_write(desc, sar, reg); lli_write(desc, dar, mem); lli_write(desc, ctlhi, ctlhi); - mem_width = __ffs(data_width | mem | dlen); + mem_width = __ffs(data_width | mem); lli_write(desc, ctllo, ctllo | DWC_CTLL_DST_WIDTH(mem_width)); desc->len = dlen; From patchwork Thu Jul 30 15:45:44 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11693351 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9FB74138A for ; Thu, 30 Jul 2020 15:46:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91F8920838 for ; Thu, 30 Jul 2020 15:46:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729962AbgG3PqL (ORCPT ); Thu, 30 Jul 2020 11:46:11 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:57404 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729952AbgG3Pp6 (ORCPT ); Thu, 30 Jul 2020 11:45:58 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 911B58040A6B; Thu, 30 Jul 2020 15:45:55 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id XMy_RAm5KOh0; Thu, 30 Jul 2020 18:45:54 +0300 (MSK) From: Serge Semin To: Vinod Koul , Viresh Kumar , Andy Shevchenko , Dan Williams CC: Serge Semin , Serge Semin , Alexey Malahov , Pavel Parkhomenko , Peter Ujfalusi , Andy Shevchenko , Rob Herring , , , Subject: [PATCH 4/5] dmaengine: dw: Ignore burst setting for memory peripherals Date: Thu, 30 Jul 2020 18:45:44 +0300 Message-ID: <20200730154545.3965-5-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> References: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org According to the DW DMA controller Databook (page 40 "3.5 Memory Peripherals") memory peripherals don't have handshaking interface connected to the controller, therefore they can never be a flow controller. Since the CTLx.SRC_MSIZE and CTLx.DEST_MSIZE are properties valid only for peripherals with a handshaking interface, we can freely zero these fields out if the memory peripheral is selected to be the source or the destination of the DMA transfers. Note according to the databook, length of burst transfers to memory is always equal to the number of data items available in a channel FIFO or data items required to complete the block transfer, whichever is smaller; length of burst transfers from memory is always equal to the space available in a channel FIFO or number of data items required to complete the block transfer, whichever is smaller. Signed-off-by: Serge Semin --- drivers/dma/dw/dw.c | 5 ++--- drivers/dma/dw/idma32.c | 5 ++--- 2 files changed, 4 insertions(+), 6 deletions(-) diff --git a/drivers/dma/dw/dw.c b/drivers/dma/dw/dw.c index d9810980920a..a4862263ff14 100644 --- a/drivers/dma/dw/dw.c +++ b/drivers/dma/dw/dw.c @@ -67,9 +67,8 @@ static size_t dw_dma_block2bytes(struct dw_dma_chan *dwc, u32 block, u32 width) static u32 dw_dma_prepare_ctllo(struct dw_dma_chan *dwc) { struct dma_slave_config *sconfig = &dwc->dma_sconfig; - bool is_slave = is_slave_direction(dwc->direction); - u8 smsize = is_slave ? sconfig->src_maxburst : DW_DMA_MSIZE_16; - u8 dmsize = is_slave ? sconfig->dst_maxburst : DW_DMA_MSIZE_16; + u8 smsize = (dwc->direction == DMA_DEV_TO_MEM) ? sconfig->src_maxburst : 0; + u8 dmsize = (dwc->direction == DMA_MEM_TO_DEV) ? sconfig->dst_maxburst : 0; u8 p_master = dwc->dws.p_master; u8 m_master = dwc->dws.m_master; u8 dms = (dwc->direction == DMA_MEM_TO_DEV) ? p_master : m_master; diff --git a/drivers/dma/dw/idma32.c b/drivers/dma/dw/idma32.c index f00657308811..3ce44de25d33 100644 --- a/drivers/dma/dw/idma32.c +++ b/drivers/dma/dw/idma32.c @@ -73,9 +73,8 @@ static size_t idma32_block2bytes(struct dw_dma_chan *dwc, u32 block, u32 width) static u32 idma32_prepare_ctllo(struct dw_dma_chan *dwc) { struct dma_slave_config *sconfig = &dwc->dma_sconfig; - bool is_slave = is_slave_direction(dwc->direction); - u8 smsize = is_slave ? sconfig->src_maxburst : IDMA32_MSIZE_8; - u8 dmsize = is_slave ? sconfig->dst_maxburst : IDMA32_MSIZE_8; + u8 smsize = (dwc->direction == DMA_DEV_TO_MEM) ? sconfig->src_maxburst : 0; + u8 dmsize = (dwc->direction == DMA_MEM_TO_DEV) ? sconfig->dst_maxburst : 0; return DWC_CTLL_LLP_D_EN | DWC_CTLL_LLP_S_EN | DWC_CTLL_DST_MSIZE(dmsize) | DWC_CTLL_SRC_MSIZE(smsize); From patchwork Thu Jul 30 15:45:45 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11693349 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C709B14B7 for ; Thu, 30 Jul 2020 15:46:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA92D20842 for ; Thu, 30 Jul 2020 15:46:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729998AbgG3PqB (ORCPT ); Thu, 30 Jul 2020 11:46:01 -0400 Received: from mail.baikalelectronics.com ([87.245.175.226]:57422 "EHLO mail.baikalelectronics.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729962AbgG3PqA (ORCPT ); Thu, 30 Jul 2020 11:46:00 -0400 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 314A480045E5; Thu, 30 Jul 2020 15:45:56 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id aBeM2cVMX9sW; Thu, 30 Jul 2020 18:45:55 +0300 (MSK) From: Serge Semin To: Vinod Koul , Viresh Kumar , Andy Shevchenko , Dan Williams CC: Serge Semin , Serge Semin , Alexey Malahov , Pavel Parkhomenko , Peter Ujfalusi , Andy Shevchenko , Rob Herring , , , Subject: [PATCH 5/5] dmaengine: dw: Add DMA-channels mask cell support Date: Thu, 30 Jul 2020 18:45:45 +0300 Message-ID: <20200730154545.3965-6-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> References: <20200730154545.3965-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org DW DMA IP-core provides a way to synthesize the DMA controller with channels having different parameters like maximum burst-length, multi-block support, maximum data width, etc. Those parameters both explicitly and implicitly affect the channels performance. Since DMA slave devices might be very demanding to the DMA performance, let's provide a functionality for the slaves to be assigned with DW DMA channels, which performance according to the platform engineer fulfill their requirements. After this patch is applied it can be done by passing the mask of suitable DMA-channels either directly in the dw_dma_slave structure instance or as a fifth cell of the DMA DT-property. If mask is zero or not provided, then there is no limitation on the channels allocation. For instance Baikal-T1 SoC is equipped with a DW DMAC engine, which first two channels are synthesized with max burst length of 16, while the rest of the channels have been created with max-burst-len=4. It would seem that the first two channels must be faster than the others and should be more preferable for the time-critical DMA slave devices. In practice it turned out that the situation is quite the opposite. The channels with max-burst-len=4 demonstrated a better performance than the channels with max-burst-len=16 even when they both had been initialized with the same settings. The performance drop of the first two DMA-channels made them unsuitable for the DW APB SSI slave device. No matter what settings they are configured with, full-duplex SPI transfers occasionally experience the Rx FIFO overflow. It means that the DMA-engine doesn't keep up with incoming data pace even though the SPI-bus is enabled with speed of 25MHz while the DW DMA controller is clocked with 50MHz signal. There is no such problem has been noticed for the channels synthesized with max-burst-len=4. Signed-off-by: Serge Semin --- drivers/dma/dw/core.c | 4 ++++ drivers/dma/dw/of.c | 7 +++++-- include/linux/platform_data/dma-dw.h | 3 +++ 3 files changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c index 3da0aea9fe25..5f7b9badb965 100644 --- a/drivers/dma/dw/core.c +++ b/drivers/dma/dw/core.c @@ -772,6 +772,10 @@ bool dw_dma_filter(struct dma_chan *chan, void *param) if (dws->dma_dev != chan->device->dev) return false; + /* permit channels in accordance with the channels mask */ + if (dws->channels && !(dws->channels & dwc->mask)) + return false; + /* We have to copy data since dws can be temporary storage */ memcpy(&dwc->dws, dws, sizeof(struct dw_dma_slave)); diff --git a/drivers/dma/dw/of.c b/drivers/dma/dw/of.c index 1474b3817ef4..abdf22b269b5 100644 --- a/drivers/dma/dw/of.c +++ b/drivers/dma/dw/of.c @@ -22,18 +22,21 @@ static struct dma_chan *dw_dma_of_xlate(struct of_phandle_args *dma_spec, }; dma_cap_mask_t cap; - if (dma_spec->args_count != 3) + if (dma_spec->args_count < 3 || dma_spec->args_count > 4) return NULL; slave.src_id = dma_spec->args[0]; slave.dst_id = dma_spec->args[0]; slave.m_master = dma_spec->args[1]; slave.p_master = dma_spec->args[2]; + if (dma_spec->args_count >= 4) + slave.channels = dma_spec->args[3]; if (WARN_ON(slave.src_id >= DW_DMA_MAX_NR_REQUESTS || slave.dst_id >= DW_DMA_MAX_NR_REQUESTS || slave.m_master >= dw->pdata->nr_masters || - slave.p_master >= dw->pdata->nr_masters)) + slave.p_master >= dw->pdata->nr_masters || + fls(slave.channels) > dw->pdata->nr_channels)) return NULL; dma_cap_zero(cap); diff --git a/include/linux/platform_data/dma-dw.h b/include/linux/platform_data/dma-dw.h index 4f681df85c27..3bc48451a70c 100644 --- a/include/linux/platform_data/dma-dw.h +++ b/include/linux/platform_data/dma-dw.h @@ -23,6 +23,8 @@ * @dst_id: dst request line * @m_master: memory master for transfers on allocated channel * @p_master: peripheral master for transfers on allocated channel + * @channels: mask of the channels permitted for allocation (zero + * value means any) * @hs_polarity:set active low polarity of handshake interface */ struct dw_dma_slave { @@ -31,6 +33,7 @@ struct dw_dma_slave { u8 dst_id; u8 m_master; u8 p_master; + u8 channels; bool hs_polarity; };