Patch "mtd: spi-nor: cadence-quadspi: Handle probe deferral while requesting DMA channel" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mtd-spi-nor-cadence-quadspi-handle-probe-deferral-wh.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 53031171931595d07ef898b336111560d99a804c
Author: Vignesh Raghavendra <vigneshr@xxxxxx>
Date:   Mon Jun 1 12:34:41 2020 +0530

    mtd: spi-nor: cadence-quadspi: Handle probe deferral while requesting DMA channel
    
    [ Upstream commit 935da5e5100f57d843cac4781b21f1c235059aa0 ]
    
    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@xxxxxx>
    Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
    Acked-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20200601070444.16923-6-vigneshr@xxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Stable-dep-of: 2087e85bb66e ("spi: cadence-quadspi: fix suspend-resume implementations")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
index ad27d3e4c5dbc..2c5a6587f505e 100644
--- a/drivers/mtd/spi-nor/cadence-quadspi.c
+++ b/drivers/mtd/spi-nor/cadence-quadspi.c
@@ -1168,7 +1168,7 @@ 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;
 
@@ -1177,11 +1177,16 @@ 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 int cqspi_setup_flash(struct cqspi_st *cqspi, struct device_node *np)
@@ -1265,8 +1270,11 @@ 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;
+			}
 		}
 	}