Re: [PATCH v3] dmaengine: qcom: bam_dma: Avoid writing unavailable register

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On 12/9/2024 4:05 PM, Manikanta Mylavarapu wrote:


On 12/9/2024 1:01 PM, Md Sadre Alam wrote:
Avoid writing unavailable register in BAM-Lite mode.
BAM_DESC_CNT_TRSHLD register is unavailable in BAM-Lite
mode. Its only available in BAM-NDP mode. So only write
this register for clients who is using BAM-NDP.

Signed-off-by: Md Sadre Alam <quic_mdalam@xxxxxxxxxxx>
---

Change in [v3]

* Removed BAM_LITE macro

* Updated commit message

* Adjusted if condition check

* Renamed BAM-NDP macro to BAM_NDP_REVISION_START and
   BAM_NDP_REVISION_END

Change in [v2]

* Replace 0xff with REVISION_MASK in the statement
   bdev->bam_revision = val & REVISION_MASK

Change in [v1]

* Added initial patch

  drivers/dma/qcom/bam_dma.c | 24 ++++++++++++++++--------
  1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
index d43a881e43b9..a00dd0331ff5 100644
--- a/drivers/dma/qcom/bam_dma.c
+++ b/drivers/dma/qcom/bam_dma.c
@@ -59,6 +59,9 @@ struct bam_desc_hw {
  #define DESC_FLAG_NWD BIT(12)
  #define DESC_FLAG_CMD BIT(11)
+#define BAM_NDP_REVISION_START 0x20
+#define BAM_NDP_REVISION_END	0x27
+
  struct bam_async_desc {
  	struct virt_dma_desc vd;
@@ -398,6 +401,7 @@ struct bam_device { /* dma start transaction tasklet */
  	struct tasklet_struct task;
+	u32 bam_revision;
  };
/**
@@ -441,8 +445,10 @@ static void bam_reset(struct bam_device *bdev)
  	writel_relaxed(val, bam_addr(bdev, 0, BAM_CTRL));
/* set descriptor threshold, start with 4 bytes */
-	writel_relaxed(DEFAULT_CNT_THRSHLD,
-			bam_addr(bdev, 0, BAM_DESC_CNT_TRSHLD));
+	if (bdev->bam_revision >= BAM_NDP_REVISION_START &&
+	    bdev->bam_revision <= BAM_NDP_REVISION_END)

Please use in_range().
Ok

+		writel_relaxed(DEFAULT_CNT_THRSHLD,
+			       bam_addr(bdev, 0, BAM_DESC_CNT_TRSHLD));
/* Enable default set of h/w workarounds, ie all except BAM_FULL_PIPE */
  	writel_relaxed(BAM_CNFG_BITS_DEFAULT, bam_addr(bdev, 0, BAM_CNFG_BITS));
@@ -1000,9 +1006,10 @@ static void bam_apply_new_config(struct bam_chan *bchan,
  			maxburst = bchan->slave.src_maxburst;
  		else
  			maxburst = bchan->slave.dst_maxburst;
-
-		writel_relaxed(maxburst,
-			       bam_addr(bdev, 0, BAM_DESC_CNT_TRSHLD));
+		if (bdev->bam_revision >= BAM_NDP_REVISION_START &&
+		    bdev->bam_revision <= BAM_NDP_REVISION_END)

Please use in_range().
Ok

Thanks & Regards,
Manikanta.





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