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

On Fri, Jan 17, 2025 at 04:43:02PM +0530, Md Sadre Alam wrote:
> 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

The 'also' sounds like the patch is fixing 2 issues, but it is just fixing one.

> 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@vger.kernel.org

The offending commit is just in the -next branch. So CCing stable is pointless.

- Mani

-- 
மணிவண்ணன் சதாசிவம்

On 1/19/2025 11:11 AM, Manivannan Sadhasivam wrote:
> On Fri, Jan 17, 2025 at 04:43:02PM +0530, Md Sadre Alam wrote:
>> 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
> 
> The 'also' sounds like the patch is fixing 2 issues, but it is just fixing one.
Will update the commit message in next revision.
> 
>> 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@vger.kernel.org
> 
> The offending commit is just in the -next branch. So CCing stable is pointless.
Ok, will remove in next revision.
> 
> - Mani
>