dmaengine: axi-dmac: check cache coherency register

Marking the DMA as cache coherent (dma-coherent in devicetree) is only
safe with versions of axi_dmac that have this feature enabled.

Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Vinod Koul <vkoul@kernel.org>
Acked-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Mathias Tausen <mta@satlab.com>
Link: https://lore.kernel.org/r/20220726140213.786939-1-mta@satlab.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: tausen

drivers/dma/dma-axi-dmac.c

@@ -18,6 +18,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_dma.h>
+#include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>
@@ -55,6 +56,9 @@
 #define   AXI_DMAC_DMA_DST_TYPE_GET(x)	FIELD_GET(AXI_DMAC_DMA_DST_TYPE_MSK, x)
 #define   AXI_DMAC_DMA_DST_WIDTH_MSK	GENMASK(3, 0)
 #define   AXI_DMAC_DMA_DST_WIDTH_GET(x)	FIELD_GET(AXI_DMAC_DMA_DST_WIDTH_MSK, x)
+#define AXI_DMAC_REG_COHERENCY_DESC	0x14
+#define   AXI_DMAC_DST_COHERENT_MSK	BIT(0)
+#define   AXI_DMAC_DST_COHERENT_GET(x)	FIELD_GET(AXI_DMAC_DST_COHERENT_MSK, x)
 
 #define AXI_DMAC_REG_IRQ_MASK		0x80
 #define AXI_DMAC_REG_IRQ_PENDING	0x84
@@ -979,6 +983,18 @@ static int axi_dmac_probe(struct platform_device *pdev)
 
 	axi_dmac_write(dmac, AXI_DMAC_REG_IRQ_MASK, 0x00);
 
+	if (of_dma_is_coherent(pdev->dev.of_node)) {
+		ret = axi_dmac_read(dmac, AXI_DMAC_REG_COHERENCY_DESC);
+
+		if (version < ADI_AXI_PCORE_VER(4, 4, 'a') ||
+		    !AXI_DMAC_DST_COHERENT_GET(ret)) {
+			dev_err(dmac->dma_dev.dev,
+				"Coherent DMA not supported in hardware");
+			ret = -EINVAL;
+			goto err_clk_disable;
+		}
+	}
+
 	ret = dma_async_device_register(dma_dev);
 	if (ret)
 		goto err_clk_disable;