Re: [PATCH v4] dmaengine: qcom: bam_dma: Avoid writing unavailable register

[Vinod Koul <vkoul@kernel.org>]

On 07-01-25, 23:30, Georgi Djakov wrote:
> On 20.12.24 11:42, 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@quicinc.com>
> > ---
> 
> My Dragonboard db845c fails to boot on recent linux-next releases and
> git bisect points to this patch. It boots again when it's reverted.

Should we revert?

> 
> [..]
> 
> >   	bchan->reconfigure = 0;
> > @@ -1192,10 +1199,11 @@ 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 & REVISION_MASK;
> 
> The problem seems to occur when we try to read the revision for the
> slimbus bam instance at 0x17184000 (which has "qcom,num-ees = <2>;").
> 
> Thanks,
> Georgi

-- 
~Vinod