FAILED: patch "[PATCH] spi: cadence-qspi: Fix probe on AM62A LP SK" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x b8665a1b49f5498edb7b21d730030c06b7348a3c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025041752-harmless-scoring-d983@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b8665a1b49f5498edb7b21d730030c06b7348a3c Mon Sep 17 00:00:00 2001
From: Miquel Raynal <[email protected]>
Date: Wed, 5 Mar 2025 21:09:32 +0100
Subject: [PATCH] spi: cadence-qspi: Fix probe on AM62A LP SK

In 2020, there's been an unnoticed change which rightfully attempted to report probe deferrals upon DMA absence by checking the return value of dma_request_chan_by_mask(). By doing so, it also reported errors which were simply ignored otherwise, likely on purpose.

This change actually turned a void return into an error code. Hence, not only the -EPROBE_DEFER error codes but all error codes got reported to the callers, now failing to probe in the absence of Rx DMA channel, despite the fact that DMA seems to not be supported natively by many implementations.

Looking at the history, this change probably led to:
ad2775dc3fc5 ("spi: cadence-quadspi: Disable the DAC for Intel LGM SoC") f724c296f2f2 ("spi: cadence-quadspi: fix Direct Access Mode disable for SoCFPGA")

In my case, the AM62A LP SK core octo-SPI node from TI does not advertise any DMA channel, hinting that there is likely no support for it, but yet when the support for the am654 compatible was added, DMA seemed to be used, so just discarding its use with the CQSPI_DISABLE_DAC_MODE quirk for this compatible does not seem the correct approach.

Let's get change the return condition back to:
- return a probe deferral error if we get one
- ignore the return value otherwise
The "error" log level was however likely too high for something that is expected to fail, so let's lower it arbitrarily to the info level.

index 0cd37a7436d5..c90462783b3f 100644
@@ -1658,6 +1658,12 @@ static int cqspi_request_mmap_dma(struct cqspi_st *cqspi)
 		int ret = PTR_ERR(cqspi->rx_chan);
 
 		cqspi->rx_chan = NULL;
+		if (ret == -ENODEV) {
+			/* DMA support is not mandatory */
+			dev_info(&cqspi->pdev->dev, "No Rx DMA available\n");
+			return 0;
+		}
+
 		return dev_err_probe(&cqspi->pdev->dev, ret, "No Rx DMA available\n");
 	}
 	init_completion(&cqspi->rx_dma_complete);