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

[Md Sadre Alam <quic_mdalam@xxxxxxxxxxx>]

On 11/23/2024 10:06 AM, Varadarajan Narayanan wrote:
> On Fri, Nov 22, 2024 at 12:46:49PM +0530, 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 avoid writing
> > this register for clients who is using BAM-Lite mode.
> >
> > Signed-off-by: Md Sadre Alam <quic_mdalam@xxxxxxxxxxx>
> > ---
> >   drivers/dma/qcom/bam_dma.c | 22 ++++++++++++++--------
> >   1 file changed, 14 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> > index d43a881e43b9..13a08c03746b 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_LITE	0x13
> > +#define BAM_NDP		0x20
> > +
> >   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 +445,9 @@ 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_LITE && bdev->bam_revision < BAM_NDP)
> > +		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 +1005,9 @@ 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_LITE && bdev->bam_revision < BAM_NDP)
> > +			writel_relaxed(maxburst,
> > +				       bam_addr(bdev, 0, BAM_DESC_CNT_TRSHLD));
> >   	}
> >
> >   	bchan->reconfigure = 0;
> > @@ -1192,10 +1197,11 @@ static int bam_init(struct bam_device *bdev)
> >   	u32 val;
> >
> >   	/* read revision and configuration information */
> > -	if (!bdev->num_ees) {
> > -		val = readl_relaxed(bam_addr(bdev, 0, BAM_REVISION));
> > +	val = readl_relaxed(bam_addr(bdev, 0, BAM_REVISION));
> > +	if (!bdev->num_ees)
> >   		bdev->num_ees = (val >> NUM_EES_SHIFT) & NUM_EES_MASK;
> > -	}
> > +
> > +	bdev->bam_revision = val & 0xff;
>
> Use REVISION_MASK instead of 0xff
Ok
> -Varada
>
> >   	/* check that configured EE is within range */
> >   	if (bdev->ee >= bdev->num_ees)
> > --
> > 2.34.1