spi: atmel: introduce probe deferring

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: Mark Brown <broonie@kernel.org>

1 files changed, 16 insertions, 4 deletions

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 3370a3dfd883..e4193ccc4970 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -427,14 +427,23 @@ static int atmel_spi_configure_dma(struct atmel_spi *as)
         dma_cap_zero(mask);
         dma_cap_set(DMA_SLAVE, mask);
 
-        as->dma.chan_tx = dma_request_slave_channel(dev, "tx");
-        if (!as->dma.chan_tx) {
+        as->dma.chan_tx = dma_request_slave_channel_reason(dev, "tx");
+        if (IS_ERR(as->dma.chan_tx)) {
+                err = PTR_ERR(as->dma.chan_tx);
+                if (err == -EPROBE_DEFER) {
+                        dev_warn(dev, "no DMA channel available at the moment\n");
+                        return err;
+                }
                 dev_err(dev,
                         "DMA TX channel not available, SPI unable to use DMA\n");
                 err = -EBUSY;
                 goto error;
         }
 
+        /*
+         * No reason to check EPROBE_DEFER here since we have already requested
+         * tx channel. If it fails here, it's for another reason.
+         */
         as->dma.chan_rx = dma_request_slave_channel(dev, "rx");
 
         if (!as->dma.chan_rx) {
@@ -456,7 +465,7 @@ static int atmel_spi_configure_dma(struct atmel_spi *as)
 error:
         if (as->dma.chan_rx)
                 dma_release_channel(as->dma.chan_rx);
-        if (as->dma.chan_tx)
+        if (!IS_ERR(as->dma.chan_tx))
                 dma_release_channel(as->dma.chan_tx);
         return err;
 }
@@ -1328,8 +1337,11 @@ static int atmel_spi_probe(struct platform_device *pdev)
         as->use_dma = false;
         as->use_pdc = false;
         if (as->caps.has_dma_support) {
-                if (atmel_spi_configure_dma(as) == 0)
+                ret = atmel_spi_configure_dma(as);
+                if (ret == 0)
                         as->use_dma = true;
+                else if (ret == -EPROBE_DEFER)
+                        return ret;
         } else {
                 as->use_pdc = true;
         }