diff mbox

[v2,07/10] dmaengine: sun6i: Retrieve channel count/max request from devicetree

Message ID 20170917031956.28010-8-stefan.bruens@rwth-aachen.de (mailing list archive)
State New, archived
Headers show

Commit Message

Stefan Brüns Sept. 17, 2017, 3:19 a.m. UTC 
To avoid introduction of a new compatible for each small SoC/DMA controller
variation, move the definition of the channel count to the devicetree.

The number of vchans is no longer explicit, but limited by the highest
port/DMA request number. The result is a slight overallocation for SoCs
with a sparse port mapping.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
---
 drivers/dma/sun6i-dma.c | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

Comments

Maxime Ripard Sept. 18, 2017, 8:18 a.m. UTC | #1 
Hi,

On Sun, Sep 17, 2017 at 05:19:53AM +0200, Stefan Brüns wrote:
> +	ret = of_property_read_u32(np, "dma-channels", &sdc->num_pchans);
> +	if (ret && !sdc->num_pchans) {
> +		dev_err(&pdev->dev, "Can't get dma-channels.\n");
> +		return ret;
> +	}
> +
> +	if (sdc->num_pchans > DMA_MAX_CHANNELS) {
> +		dev_err(&pdev->dev, "Number of dma-channels out of range.\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = of_property_read_u32(np, "dma-requests", &sdc->max_request);
> +	if (ret && !sdc->max_request) {
> +		dev_info(&pdev->dev, "Missing dma-requests, using %u.\n",
> +			 DMA_CHAN_MAX_DRQ);
> +		sdc->max_request = DMA_CHAN_MAX_DRQ;
> +	}
> +
> +	if (sdc->max_request > DMA_CHAN_MAX_DRQ) {
> +		dev_err(&pdev->dev, "Value of dma-requests out of range.\n");
> +		return -EINVAL;
> +	}

I'm not really convinced about these two checks. They don't catch all
errors (the range between the actual number of channels / DRQ and the
maximum allowed per the registers), they might increase in the future
too, and if we want to make that check actually working, we would have
to duplicate the number of requests and channels into the driver.

Which is kind of the opposite of what we're trying to do here :)

Once removed,
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Maxime
diff mbox

Patch

diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
index 245a147f718f..b5ecc97a0d5a 100644
--- a/drivers/dma/sun6i-dma.c
+++ b/drivers/dma/sun6i-dma.c
@@ -42,6 +42,9 @@ 
 
 #define DMA_STAT		0x30
 
+/* Offset between DMA_IRQ_EN and DMA_IRQ_STAT limits number of channels */
+#define DMA_MAX_CHANNELS	(DMA_IRQ_CHAN_NR * 0x10 / 4)
+
 /*
  * sun8i specific registers
  */
@@ -65,7 +68,8 @@ 
 #define DMA_CHAN_LLI_ADDR	0x08
 
 #define DMA_CHAN_CUR_CFG	0x0c
-#define DMA_CHAN_CFG_SRC_DRQ(x)		((x) & 0x1f)
+#define DMA_CHAN_MAX_DRQ		0x1f
+#define DMA_CHAN_CFG_SRC_DRQ(x)		((x) & DMA_CHAN_MAX_DRQ)
 #define DMA_CHAN_CFG_SRC_IO_MODE	BIT(5)
 #define DMA_CHAN_CFG_SRC_LINEAR_MODE	(0 << 5)
 #define DMA_CHAN_CFG_SRC_BURST_A31(x)	(((x) & 0x3) << 7)
@@ -1157,6 +1161,7 @@  MODULE_DEVICE_TABLE(of, sun6i_dma_match);
 static int sun6i_dma_probe(struct platform_device *pdev)
 {
 	const struct of_device_id *device;
+	struct device_node *np = pdev->dev.of_node;
 	struct sun6i_dma_dev *sdc;
 	struct resource *res;
 	int ret, i;
@@ -1232,6 +1237,36 @@  static int sun6i_dma_probe(struct platform_device *pdev)
 	sdc->num_vchans = sdc->cfg->nr_max_vchans;
 	sdc->max_request = sdc->cfg->nr_max_requests;
 
+	ret = of_property_read_u32(np, "dma-channels", &sdc->num_pchans);
+	if (ret && !sdc->num_pchans) {
+		dev_err(&pdev->dev, "Can't get dma-channels.\n");
+		return ret;
+	}
+
+	if (sdc->num_pchans > DMA_MAX_CHANNELS) {
+		dev_err(&pdev->dev, "Number of dma-channels out of range.\n");
+		return -EINVAL;
+	}
+
+	ret = of_property_read_u32(np, "dma-requests", &sdc->max_request);
+	if (ret && !sdc->max_request) {
+		dev_info(&pdev->dev, "Missing dma-requests, using %u.\n",
+			 DMA_CHAN_MAX_DRQ);
+		sdc->max_request = DMA_CHAN_MAX_DRQ;
+	}
+
+	if (sdc->max_request > DMA_CHAN_MAX_DRQ) {
+		dev_err(&pdev->dev, "Value of dma-requests out of range.\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * If the number of vchans is not specified, derive it from the
+	 * highest port number, at most one channel per port and direction.
+	 */
+	if (!sdc->num_vchans)
+		sdc->num_vchans = 2 * (sdc->max_request + 1);
+
 	sdc->pchans = devm_kcalloc(&pdev->dev, sdc->num_pchans,
 				   sizeof(struct sun6i_pchan), GFP_KERNEL);
 	if (!sdc->pchans)