linux-kernel - [PATCH] dmaengine: qcom: bam_dma: keep remotely controlled units on during boot

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Message-Id: <20250503-bam-dma-reset-v1-1-266b6cecb844@oss.qualcomm.com>
Date: Sat, 03 May 2025 03:41:43 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Vinod Koul <vkoul@...nel.org>, Caleb Connolly <caleb.connolly@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] dmaengine: qcom: bam_dma: keep remotely controlled units
 on during boot

The commit 0ac9c3dd0d6f ("dmaengine: qcom: bam_dma: fix runtime PM
underflow") made sure the BAM DMA device gets suspended, disabling the
bam_clk. However for remotely controlled BAM DMA devices the clock might
be disabled prematurely (e.g. in case of the earlycon this frequently
happens before UART driver is able to probe), which causes device reset.

Use sync_state callback to ensure that bam_clk stays on until all users
are probed (and are able to vote upon corresponding clocks).

Fixes: 0ac9c3dd0d6f ("dmaengine: qcom: bam_dma: fix runtime PM underflow")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
---
 drivers/dma/qcom/bam_dma.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index bbc3276992bb012a1b79937bdbd069fc01f75331..09ef450a9fb8e3efe6e664eb17caffb0bd337f84 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -1367,6 +1367,9 @@ static int bam_dma_probe(struct platform_device *pdev)
 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 
+	if (bdev->controlled_remotely || bdev->powered_remotely)
+		pm_runtime_get_sync(&pdev->dev);
+
 	return 0;
 
 err_unregister_dma:
@@ -1414,6 +1417,16 @@ static void bam_dma_remove(struct platform_device *pdev)
 	clk_disable_unprepare(bdev->bamclk);
 }
 
+static void bam_dma_sync_state(struct device *dev)
+{
+	struct bam_device *bdev = dev_get_drvdata(dev);
+
+	if (bdev->controlled_remotely || bdev->powered_remotely) {
+		pm_runtime_mark_last_busy(bdev->dev);
+		pm_runtime_put_autosuspend(bdev->dev);
+	}
+}
+
 static int __maybe_unused bam_dma_runtime_suspend(struct device *dev)
 {
 	struct bam_device *bdev = dev_get_drvdata(dev);
@@ -1474,6 +1487,7 @@ static struct platform_driver bam_dma_driver = {
 		.name = "bam-dma-engine",
 		.pm = &bam_dma_pm_ops,
 		.of_match_table = bam_of_match,
+		.sync_state = bam_dma_sync_state,
 	},
 };
 

---
base-commit: 6ac908f24cd7ddae52c496bbc888e97ee7b033ac
change-id: 20250503-bam-dma-reset-1766d2d12cec

Best regards,
-- 
Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>