linux-kernel - [PATCH v2] dmaengine: qcom: bam_dma: Fix BAM

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Message-ID: <20250117111302.2073993-1-quic_mdalam@quicinc.com>
Date: Fri, 17 Jan 2025 16:43:02 +0530
From: Md Sadre Alam <quic_mdalam@...cinc.com>
To: <vkoul@...nel.org>, <robin.murphy@....com>,
        <linux-arm-msm@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC: <quic_mdalam@...cinc.com>, <quic_varada@...cinc.com>,
        <quic_srichara@...cinc.com>
Subject: [PATCH v2] dmaengine: qcom: bam_dma: Fix BAM_RIVISON register handling

This patch resolves a bug from the previous commit where the
BAM_DESC_CNT_TRSHLD register was conditionally written based on BAM-NDP
mode. It also fixes an issue where reading the BAM_REVISION register
would hang if num-ees was not zero, which occurs when the SoCs power on
BAM remotely. The BAM_REVISION register read has been moved to inside if
condition.

Cc: stable@...r.kernel.org
Fixes: 57a7138d0627 ("dmaengine: qcom: bam_dma: Avoid writing unavailable register")
Reported-by: Georgi Djakov <djakov@...nel.org>
Link: https://lore.kernel.org/lkml/9ef3daa8-cdb1-49f2-8d19-a72d6210ff3a@kernel.org/
Signed-off-by: Md Sadre Alam <quic_mdalam@...cinc.com>
---

Change in [v2]

* Removed unnecessary if checks.
* Relocated the BAM_REVISION register read within the if condition.

Change in [v1]

* https://lore.kernel.org/lkml/1a5fc7e9-39fe-e527-efc3-1ea990bbb53b@quicinc.com/
* Posted initial fixup for BAM revision register read handling

 drivers/dma/qcom/bam_dma.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index c14557efd577..d227b4f5b6b9 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -1199,11 +1199,11 @@ static int bam_init(struct bam_device *bdev)
 	u32 val;
 
 	/* read revision and configuration information */
-	val = readl_relaxed(bam_addr(bdev, 0, BAM_REVISION));
-	if (!bdev->num_ees)
+	if (!bdev->num_ees) {
+		val = readl_relaxed(bam_addr(bdev, 0, BAM_REVISION));
 		bdev->num_ees = (val >> NUM_EES_SHIFT) & NUM_EES_MASK;
-
-	bdev->bam_revision = val & REVISION_MASK;
+		bdev->bam_revision = val & REVISION_MASK;
+	}
 
 	/* check that configured EE is within range */
 	if (bdev->ee >= bdev->num_ees)
-- 
2.34.1