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

[Caleb Connolly <caleb.connolly@xxxxxxxxxx>]

On 2/8/25 22:30, Caleb Connolly wrote:
> This commit causes a hard crash on sdm845 and likely other platforms.
> Revert it until a proper fix is found.
>
> This reverts commit 57a7138d0627309d469719f1845d2778c251f358.
>
> Signed-off-by: Caleb Connolly <caleb.connolly@xxxxxxxxxx>

Missing fixes tag

Fixes: 57a7138d0627 (dmaengine: qcom: bam_dma: Avoid writing unavailable 
register)
> ---
>   drivers/dma/qcom/bam_dma.c | 24 ++++++++----------------
>   1 file changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index c14557efd577..bbc3276992bb 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -58,11 +58,8 @@ struct bam_desc_hw {
>   #define DESC_FLAG_EOB BIT(13)
>   #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;
>   
>   	u32 num_desc;
> @@ -400,9 +397,8 @@ struct bam_device {
>   	int irq;
>   
>   	/* dma start transaction tasklet */
>   	struct tasklet_struct task;
> -	u32 bam_revision;
>   };
>   
>   /**
>    * bam_addr - returns BAM register address
> @@ -444,12 +440,10 @@ static void bam_reset(struct bam_device *bdev)
>   	val |= BAM_EN;
>   	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));
>   
> @@ -1005,12 +999,11 @@ static void bam_apply_new_config(struct bam_chan *bchan,
>   		if (dir == DMA_DEV_TO_MEM)
>   			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;
>   }
> @@ -1198,13 +1191,12 @@ 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)
>   		return -EINVAL;

--
Caleb (they/them)