diff mbox series

dmaengine: axi-dmac: Sanity check memory mapped interface support

Message ID 20190516083134.29460-1-alexandru.ardelean@analog.com (mailing list archive)
State Accepted
Headers show
Series dmaengine: axi-dmac: Sanity check memory mapped interface support | expand

Commit Message

Alexandru Ardelean May 16, 2019, 8:31 a.m. UTC 
From: Lars-Peter Clausen <lars@metafoo.de>

The AXI-DMAC supports different types of interface for the data source and
destination ports. Typically one of those ports is a memory-mapped
interface while the other is some kind of streaming interface.

The information about which kind of interface is used for each port is
encoded in the devicetree.

It is also possible in the driver to detect whether a port supports
memory-mapped transfers or not. For streaming interfaces the address
register is read-only and will always return 0. So in order to check if a
port supports memory-mapped transfers write a non-zero value to the
corresponding address register and check that the value read-back is still
non zero.

This allows to detect mismatches between the devicetree description and the
actual hardware configuration.

Unfortunately it is not possible to autodetect the interface types since
there is no method to distinguish between the different streaming ports. So
the best thing that can be done is to error out when a memory mapped port
is described in the devicetree but none is detected in the hardware.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/dma/dma-axi-dmac.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

Comments

Vinod Koul May 21, 2019, 5:08 a.m. UTC | #1 
On 16-05-19, 11:31, Alexandru Ardelean wrote:
> From: Lars-Peter Clausen <lars@metafoo.de>
> 
> The AXI-DMAC supports different types of interface for the data source and
> destination ports. Typically one of those ports is a memory-mapped
> interface while the other is some kind of streaming interface.
> 
> The information about which kind of interface is used for each port is
> encoded in the devicetree.
> 
> It is also possible in the driver to detect whether a port supports
> memory-mapped transfers or not. For streaming interfaces the address
> register is read-only and will always return 0. So in order to check if a
> port supports memory-mapped transfers write a non-zero value to the
> corresponding address register and check that the value read-back is still
> non zero.
> 
> This allows to detect mismatches between the devicetree description and the
> actual hardware configuration.
> 
> Unfortunately it is not possible to autodetect the interface types since
> there is no method to distinguish between the different streaming ports. So
> the best thing that can be done is to error out when a memory mapped port
> is described in the devicetree but none is detected in the hardware.

Applied, thanks
diff mbox series

Patch

diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
index f32fdf21edbd..5710179a401e 100644
--- a/drivers/dma/dma-axi-dmac.c
+++ b/drivers/dma/dma-axi-dmac.c
@@ -632,7 +632,7 @@  static int axi_dmac_parse_chan_dt(struct device_node *of_chan,
 	return 0;
 }
 
-static void axi_dmac_detect_caps(struct axi_dmac *dmac)
+static int axi_dmac_detect_caps(struct axi_dmac *dmac)
 {
 	struct axi_dmac_chan *chan = &dmac->chan;
 
@@ -648,6 +648,24 @@  static void axi_dmac_detect_caps(struct axi_dmac *dmac)
 	chan->max_length = axi_dmac_read(dmac, AXI_DMAC_REG_X_LENGTH);
 	if (chan->max_length != UINT_MAX)
 		chan->max_length++;
+
+	axi_dmac_write(dmac, AXI_DMAC_REG_DEST_ADDRESS, 0xffffffff);
+	if (axi_dmac_read(dmac, AXI_DMAC_REG_DEST_ADDRESS) == 0 &&
+	    chan->dest_type == AXI_DMAC_BUS_TYPE_AXI_MM) {
+		dev_err(dmac->dma_dev.dev,
+			"Destination memory-mapped interface not supported.");
+		return -ENODEV;
+	}
+
+	axi_dmac_write(dmac, AXI_DMAC_REG_SRC_ADDRESS, 0xffffffff);
+	if (axi_dmac_read(dmac, AXI_DMAC_REG_SRC_ADDRESS) == 0 &&
+	    chan->src_type == AXI_DMAC_BUS_TYPE_AXI_MM) {
+		dev_err(dmac->dma_dev.dev,
+			"Source memory-mapped interface not supported.");
+		return -ENODEV;
+	}
+
+	return 0;
 }
 
 static int axi_dmac_probe(struct platform_device *pdev)
@@ -723,7 +741,9 @@  static int axi_dmac_probe(struct platform_device *pdev)
 	if (ret < 0)
 		return ret;
 
-	axi_dmac_detect_caps(dmac);
+	ret = axi_dmac_detect_caps(dmac);
+	if (ret)
+		goto err_clk_disable;
 
 	axi_dmac_write(dmac, AXI_DMAC_REG_IRQ_MASK, 0x00);