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

[Md Sadre Alam <quic_mdalam@quicinc.com>]

On 1/8/2025 4:40 PM, Vinod Koul wrote:
> 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?
I have posted the fix. Patch available at [1]
[1] 
https://patchwork.kernel.org/project/linux-arm-msm/patch/20250110051409.4099727-1-quic_mdalam@quicinc.com/
> 
>>
>> [..]
>>
>>>    	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
>