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>

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 3370a3dfd883a50b0006afda784fa1ebc7e10f5d..e4193ccc4970634f32e4ddec97bef7775c802204 100644 (file)
--- 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;
        }