dmaengine: Revert "dmaengine: qcom: bam_dma: Avoid writing unavailable register"

commit e521f51
Author: Caleb Connolly <[email protected]>
Date: Sat Feb 8 22:30:54 2025 +0000

    dmaengine: Revert "dmaengine: qcom: bam_dma: Avoid writing unavailable register"

    This commit causes a hard crash on sdm845 and likely other platforms.
    Revert it until a proper fix is found.

    This reverts commit 57a7138: ("dmaengine: qcom: bam_dma: Avoid writing
    unavailable register")

    Signed-off-by: Caleb Connolly <[email protected]>
    Fixes: 57a7138 ("dmaengine: qcom: bam_dma: Avoid writing unavailable register")
    Tested-by: Neil Armstrong <[email protected]> # on sdm845-DB845c
    Tested-by: David Heidelberg <[email protected]>
    Link: https://lore.kernel.org/r/[email protected]
    Signed-off-by: Vinod Koul <[email protected]>

(cherry picked from commit e521f51)
Signed-off-by: Jerry Snitselaar <[email protected]>
JIRA: https://issues.redhat.com/browse/RHEL-78706
Upstream-Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

Author: snits

drivers/dma/qcom/bam_dma.c

@@ -59,9 +59,6 @@ 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;
 
@@ -401,7 +398,6 @@ struct bam_device {
 
 	/* dma start transaction tasklet */
 	struct tasklet_struct task;
-	u32 bam_revision;
 };
 
 /**
@@ -445,10 +441,8 @@ static void bam_reset(struct bam_device *bdev)
 	writel_relaxed(val, bam_addr(bdev, 0, BAM_CTRL));
 
 	/* set descriptor threshold, start with 4 bytes */
-	if (in_range(bdev->bam_revision, BAM_NDP_REVISION_START,
-		     BAM_NDP_REVISION_END))
-		writel_relaxed(DEFAULT_CNT_THRSHLD,
-			       bam_addr(bdev, 0, BAM_DESC_CNT_TRSHLD));
+	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));
@@ -1006,10 +1000,9 @@ static void bam_apply_new_config(struct bam_chan *bchan,
 			maxburst = bchan->slave.src_maxburst;
 		else
 			maxburst = bchan->slave.dst_maxburst;
-		if (in_range(bdev->bam_revision, BAM_NDP_REVISION_START,
-			     BAM_NDP_REVISION_END))
-			writel_relaxed(maxburst,
-				       bam_addr(bdev, 0, BAM_DESC_CNT_TRSHLD));
+
+		writel_relaxed(maxburst,
+			       bam_addr(bdev, 0, BAM_DESC_CNT_TRSHLD));
 	}
 
 	bchan->reconfigure = 0;
@@ -1199,11 +1192,10 @@ 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;
+	}
 
 	/* check that configured EE is within range */
 	if (bdev->ee >= bdev->num_ees)