dmaengine: jz4780: Work around hardware bug on JZ4760 SoCs

The JZ4760 SoC has a hardware problem with chan0 not enabling properly
if it's enabled before chan1, after a reset (works fine afterwards).
This is worked around in the probe function by just enabling then
disabling chan1.

Signed-off-by: Paul Cercueil <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

drivers/dma/dma-jz4780.c

@@ -938,6 +938,14 @@ static int jz4780_dma_probe(struct platform_device *pdev)
 		jzchan->vchan.desc_free = jz4780_dma_desc_free;
 	}
 
+	/*
+	 * On JZ4760, chan0 won't enable properly the first time.
+	 * Enabling then disabling chan1 will magically make chan0 work
+	 * correctly.
+	 */
+	jz4780_dma_chan_enable(jzdma, 1);
+	jz4780_dma_chan_disable(jzdma, 1);
+
 	ret = platform_get_irq(pdev, 0);
 	if (ret < 0)
 		goto err_disable_clk;