mtd: spi-nor: cadence-quadspi: Handle probe deferral while requesting DMA channel

dma_request_chan_by_mask() can throw EPROBE_DEFER if DMA provider
is not yet probed. Currently driver just falls back to using PIO mode
(which is less efficient) in this case. Instead return probe deferral
error as is so that driver will be re probed once DMA provider is
available.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200601070444.16923-6-vigneshr@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/mtd/spi-nor/controllers/cadence-quadspi.c b/drivers/mtd/spi-nor/controllers/cadence-quadspi.c
index 608ca657ff7f5b9a6333e55a55af674eaef4586f..0570ebca135a9212a317fc37beba98a16fed3ba4 100644 (file)
--- a/drivers/mtd/spi-nor/controllers/cadence-quadspi.c
+++ b/drivers/mtd/spi-nor/controllers/cadence-quadspi.c
@@ -1169,7 +1169,7 @@ static void cqspi_controller_init(struct cqspi_st *cqspi)
        cqspi_controller_enable(cqspi, 1);
 }
 
-static void cqspi_request_mmap_dma(struct cqspi_st *cqspi)
+static int cqspi_request_mmap_dma(struct cqspi_st *cqspi)
 {
        dma_cap_mask_t mask;
 
@@ -1178,11 +1178,16 @@ static void cqspi_request_mmap_dma(struct cqspi_st *cqspi)
 
        cqspi->rx_chan = dma_request_chan_by_mask(&mask);
        if (IS_ERR(cqspi->rx_chan)) {
-               dev_err(&cqspi->pdev->dev, "No Rx DMA available\n");
+               int ret = PTR_ERR(cqspi->rx_chan);
+
+               if (ret != -EPROBE_DEFER)
+                       dev_err(&cqspi->pdev->dev, "No Rx DMA available\n");
                cqspi->rx_chan = NULL;
-               return;
+               return ret;
        }
        init_completion(&cqspi->rx_dma_complete);
+
+       return 0;
 }
 
 static const struct spi_nor_controller_ops cqspi_controller_ops = {
@@ -1269,8 +1274,11 @@ static int cqspi_setup_flash(struct cqspi_st *cqspi, struct device_node *np)
                        dev_dbg(nor->dev, "using direct mode for %s\n",
                                mtd->name);
 
-                       if (!cqspi->rx_chan)
-                               cqspi_request_mmap_dma(cqspi);
+                       if (!cqspi->rx_chan) {
+                               ret = cqspi_request_mmap_dma(cqspi);
+                               if (ret == -EPROBE_DEFER)
+                                       goto err;
+                       }
                }
        }