linux-kernel - [PATCH 23/25] dmaengine: dw-edma: Bypass dma-ranges mapping for the local setup

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Message-ID: <20220324014836.19149-24-Sergey.Semin@baikalelectronics.ru>
Date:   Thu, 24 Mar 2022 04:48:34 +0300
From:   Serge Semin <Sergey.Semin@...kalelectronics.ru>
To:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Vinod Koul <vkoul@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
CC:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        <linux-pci@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 23/25] dmaengine: dw-edma: Bypass dma-ranges mapping for the local setup

DW eDMA doesn't perform any translation of the traffic generated on the
CPU/Application side. It just generates read/write AXI-bus requests with
the specified addresses. But in case if the dma-ranges DT-property is
specified for a platform device node, Linux will use it to map the CPU
memory regions into the DMAable bus ranges. This isn't what we want for
the eDMA embedded into the locally accessed DW PCIe Root Port and
End-point. In order to work that around let's set the chan_dma_dev flag
for each DW eDMA channel thus forcing the client drivers to getting a
custom dma-ranges-less parental device for the mappings.

Note it will only work for the client drivers using the
dmaengine_get_dma_device() method to get the parental DMA device.

Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
---
 drivers/dma/dw-edma/dw-edma-core.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 72a51970bfba..ca5cd7c99571 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -716,6 +716,21 @@ static int dw_edma_alloc_chan_resources(struct dma_chan *dchan)
 	if (chan->status != EDMA_ST_IDLE)
 		return -EBUSY;
 
+	/* Bypass the dma-ranges based memory regions mapping since the
+	 * inbound iATU only affects the traffic incoming from the
+	 * PCIe bus.
+	 */
+	if (chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) {
+		dchan->dev->chan_dma_dev = true;
+
+		dchan->dev->device.dma_coherent = chan->dw->chip->dev->dma_coherent;
+		dma_coerce_mask_and_coherent(&dchan->dev->device,
+					     dma_get_mask(chan->dw->chip->dev));
+		dchan->dev->device.dma_parms = chan->dw->chip->dev->dma_parms;
+	} else {
+		dchan->dev->chan_dma_dev = false;
+	}
+
 	pm_runtime_get(chan->dw->chip->dev);
 
 	return 0;
-- 
2.35.1