mmc: atmel-mci: use probe deferring if dma controller is not ready yet

Return probe defer if requesting a dma channel without a dma controller
probed.
Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/atmel-mci.c

@@ -2272,18 +2272,14 @@ static void atmci_cleanup_slot(struct atmel_mci_slot *slot,
 	mmc_free_host(slot->mmc);
 }
 
-static bool atmci_configure_dma(struct atmel_mci *host)
+static int atmci_configure_dma(struct atmel_mci *host)
 {
-	if (host == NULL)
-		return false;
+	host->dma.chan = dma_request_slave_channel_reason(&host->pdev->dev,
+							"rxtx");
+	if (IS_ERR(host->dma.chan))
+		return PTR_ERR(host->dma.chan);
 
-	host->dma.chan = dma_request_slave_channel(&host->pdev->dev, "rxtx");
-	if (!host->dma.chan) {
-		dev_warn(&host->pdev->dev, "no DMA channel available\n");
-		return false;
-	} else {
-		dev_info(&host->pdev->dev,
-					"using %s for DMA transfers\n",
+	dev_info(&host->pdev->dev, "using %s for DMA transfers\n",
 		 dma_chan_name(host->dma.chan));
 
 	host->dma_conf.src_addr = host->mapbase + ATMCI_RDR;
@@ -2293,8 +2289,8 @@ static bool atmci_configure_dma(struct atmel_mci *host)
 	host->dma_conf.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 	host->dma_conf.dst_maxburst = 1;
 	host->dma_conf.device_fc = false;
-		return true;
-	}
+
+	return 0;
 }
 
 /*
@@ -2411,7 +2407,10 @@ static int atmci_probe(struct platform_device *pdev)
 
 	/* Get MCI capabilities and set operations according to it */
 	atmci_get_cap(host);
-	if (atmci_configure_dma(host)) {
+	ret = atmci_configure_dma(host);
+	if (ret == -EPROBE_DEFER)
+		goto err_dma_probe_defer;
+	if (ret == 0) {
 		host->prepare_data = &atmci_prepare_data_dma;
 		host->submit_data = &atmci_submit_data_dma;
 		host->stop_transfer = &atmci_stop_transfer_dma;
@@ -2496,8 +2495,9 @@ static int atmci_probe(struct platform_device *pdev)
 	pm_runtime_put_noidle(&pdev->dev);
 
 	del_timer_sync(&host->timer);
-	if (host->dma.chan)
+	if (!IS_ERR(host->dma.chan))
 		dma_release_channel(host->dma.chan);
+err_dma_probe_defer:
 	free_irq(irq, host);
 	return ret;
 }
@@ -2523,7 +2523,7 @@ static int atmci_remove(struct platform_device *pdev)
 	atmci_readl(host, ATMCI_SR);
 
 	del_timer_sync(&host->timer);
-	if (host->dma.chan)
+	if (!IS_ERR(host->dma.chan))
 		dma_release_channel(host->dma.chan);
 
 	free_irq(platform_get_irq(pdev, 0), host);