On Wednesday 05 October 2016 12:01 PM, Peter Ujfalusi wrote:

On 10/05/16 09:21, Mugunthan V N wrote:

quoted

On Tuesday 04 October 2016 02:02 PM, Peter Ujfalusi wrote:

quoted

On 10/03/16 16:03, Mugunthan V N wrote:

quoted

+static int tiadc_request_dma(struct platform_device *pdev,
+			     struct tiadc_device *adc_dev)
+{
+	struct tiadc_dma	*dma = &adc_dev->dma;
+	dma_cap_mask_t		mask;
+
+	/* Default slave configuration parameters */
+	dma->conf.direction = DMA_DEV_TO_MEM;
+	dma->conf.src_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTES;
+	dma->conf.src_addr = adc_dev->mfd_tscadc->tscadc_phys_base + REG_FIFO1;
+
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_CYCLIC, mask);
+
+	/* Get a channel for RX */
+	dma->chan = dma_request_chan(adc_dev->mfd_tscadc->dev, "fifo1");
+	if (!dma->chan)
+		return -ENODEV;

dma_request_chan() ERR_PTR in case of failure, never NULL. You should reuse
the returned error code to support deferred probing.

Will fix this in v3.

quoted

quoted

+
+	/* RX buffer */
+	dma->buf = dma_alloc_coherent(dma->chan->device->dev, DMA_BUFFER_SIZE,
+				      &dma->addr, GFP_KERNEL);
+	if (!dma->buf)
+		goto err;
+
+	return 0;
+err:
+	dma_release_channel(dma->chan);
+
+	return -ENOMEM;
+}
+
 static int tiadc_parse_dt(struct platform_device *pdev,
 			  struct tiadc_device *adc_dev)
 {

@@ -512,8 +639,14 @@ static int tiadc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, indio_dev);
 
+	err = tiadc_request_dma(pdev, adc_dev);
+	if (err && err != -ENODEV)
+		goto err_dma;

You should handle the deferred probing for DMA channel.

+	dma->chan = dma_request_chan(adc_dev->mfd_tscadc->dev, "fifo1");
+	if (IS_ERR(dma->chan)) {
+		int ret = PTR_ERR(dma->chan);
+
+		dma->chan = NULL;
+		return ret;

You don't need the 'ret' variable:
		return PTR_ERR(dma->chan);

So you mean change all *if (dma->chan)* to *if (IS_ERR(dma->chan))*?

quoted

+	}

With this probe defer will be taken care and ADC will continue without
DMA when request channel returns -ENODEV.

I would rather have explicit check for deferred probe:

err = tiadc_request_dma(pdev, adc_dev);
if (err && err == -EPROBE_DEFER)
	goto err_dma;

But in this case any other failure other than -EPROBE_DEFER will be
masked and ADC will be in PIO mode?

Regards
Mugunthan V N