dmaengine Archive on lore.kernel.org
 help / color / Atom feed
From: Serge Semin <Sergey.Semin@baikalelectronics.ru>
To: Vinod Koul <vkoul@kernel.org>, Viresh Kumar <vireshk@kernel.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Dan Williams <dan.j.williams@intel.com>
Cc: Serge Semin <Sergey.Semin@baikalelectronics.ru>,
	Serge Semin <fancer.lancer@gmail.com>,
	Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
	Pavel Parkhomenko <Pavel.Parkhomenko@baikalelectronics.ru>,
	Peter Ujfalusi <peter.ujfalusi@ti.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Rob Herring <robh+dt@kernel.org>, <dmaengine@vger.kernel.org>,
	<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: [PATCH v2 4/5] dmaengine: dw: Ignore burst setting for memory peripherals
Date: Fri, 31 Jul 2020 23:08:25 +0300
Message-ID: <20200731200826.9292-5-Sergey.Semin@baikalelectronics.ru> (raw)
In-Reply-To: <20200731200826.9292-1-Sergey.Semin@baikalelectronics.ru>

According to the DW DMA controller Databook 2.18b (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 <Sergey.Semin@baikalelectronics.ru>

---

Changelog v2:
- Add Databook version to the commit log.
---
 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);
-- 
2.27.0


  parent reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-31 20:08 [PATCH v2 0/5] dmaengine: dw: Introduce non-mem peripherals optimizations Serge Semin
2020-07-31 20:08 ` [PATCH v2 1/5] dt-bindings: dma: dw: Add optional DMA-channels mask cell support Serge Semin
2020-08-03 21:51   ` Rob Herring
2020-07-31 20:08 ` [PATCH v2 2/5] dmaengine: dw: Activate FIFO-mode for memory peripherals only Serge Semin
2020-07-31 20:08 ` [PATCH v2 3/5] dmaengine: dw: Discard dlen from the dev-to-mem xfer width calculation Serge Semin
2020-07-31 20:08 ` Serge Semin [this message]
2020-07-31 20:08 ` [PATCH v2 5/5] dmaengine: dw: Add DMA-channels mask cell support Serge Semin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200731200826.9292-5-Sergey.Semin@baikalelectronics.ru \
    --to=sergey.semin@baikalelectronics.ru \
    --cc=Alexey.Malahov@baikalelectronics.ru \
    --cc=Pavel.Parkhomenko@baikalelectronics.ru \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=andy.shevchenko@gmail.com \
    --cc=dan.j.williams@intel.com \
    --cc=devicetree@vger.kernel.org \
    --cc=dmaengine@vger.kernel.org \
    --cc=fancer.lancer@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=peter.ujfalusi@ti.com \
    --cc=robh+dt@kernel.org \
    --cc=vireshk@kernel.org \
    --cc=vkoul@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

dmaengine Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dmaengine/0 dmaengine/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dmaengine dmaengine/ https://lore.kernel.org/dmaengine \
		dmaengine@vger.kernel.org
	public-inbox-index dmaengine

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.dmaengine


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git