dmaengine: qcom: bam_dma: Fix DT error handling for num-channels/ees

JIRA: https://issues.redhat.com/browse/RHEL-114133
Upstream-Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

commit 5068b52
Author: Stephan Gerhold <stephan.gerhold@linaro.org>
Date: Wed Feb 12 18:03:54 2025 +0100

    dmaengine: qcom: bam_dma: Fix DT error handling for num-channels/ees

    When we don't have a clock specified in the device tree, we have no way to
    ensure the BAM is on. This is often the case for remotely-controlled or
    remotely-powered BAM instances. In this case, we need to read num-channels
    from the DT to have all the necessary information to complete probing.

    However, at the moment invalid device trees without clock and without
    num-channels still continue probing, because the error handling is missing
    return statements. The driver will then later try to read the number of
    channels from the registers. This is unsafe, because it relies on boot
    firmware and lucky timing to succeed. Unfortunately, the lack of proper
    error handling here has been abused for several Qualcomm SoCs upstream,
    causing early boot crashes in several situations [1, 2].

    Avoid these early crashes by erroring out when any of the required DT
    properties are missing. Note that this will break some of the existing DTs
    upstream (mainly BAM instances related to the crypto engine). However,
    clearly these DTs have never been tested properly, since the error in the
    kernel log was just ignored. It's safer to disable the crypto engine for
    these broken DTBs.

    [1]: https://lore.kernel.org/r/CY01EKQVWE36.B9X5TDXAREPF@fairphone.com/
    [2]: https://lore.kernel.org/r/20230626145959.646747-1-krzysztof.kozlowski@linaro.org/

    Cc: stable@vger.kernel.org
    Fixes: 48d163b ("dmaengine: qcom: bam_dma: get num-channels and num-ees from dt")
    Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
    Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
    Link: https://lore.kernel.org/r/20250212-bam-dma-fixes-v1-8-f560889e65d8@linaro.org
    Signed-off-by: Vinod Koul <vkoul@kernel.org>

(cherry picked from commit 5068b52)
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>

Author: snits

drivers/dma/qcom/bam_dma.c

@@ -1275,13 +1275,17 @@ static int bam_dma_probe(struct platform_device *pdev)
 	if (bdev->controlled_remotely || bdev->powered_remotely) {
 		ret = of_property_read_u32(pdev->dev.of_node, "num-channels",
 					   &bdev->num_channels);
-		if (ret)
+		if (ret) {
 			dev_err(bdev->dev, "num-channels unspecified in dt\n");
+			return ret;
+		}
 
 		ret = of_property_read_u32(pdev->dev.of_node, "qcom,num-ees",
 					   &bdev->num_ees);
-		if (ret)
+		if (ret) {
 			dev_err(bdev->dev, "num-ees unspecified in dt\n");
+			return ret;
+		}
 	}
 
 	if (bdev->controlled_remotely || bdev->powered_remotely)