[PATCH v2 3/6] dmaengine: jz4780: Work around hardware bug on JZ4760 SoCs

Paul Cercueil
2021-12-06T17:43:38Z

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 <paul@crapouillou.net>
---
drivers/dma/dma-jz4780.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index 96701dedcac8..d63753a56541 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/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;
--
2.33.0