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

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Message-ID: <0b93ee40-0d1e-a137-c049-ac5adcc81e54@quicinc.com>
Date: Wed, 8 Jan 2025 16:44:59 +0530
From: Md Sadre Alam <quic_mdalam@...cinc.com>
To: Vinod Koul <vkoul@...nel.org>, Georgi Djakov <djakov@...nel.org>
CC: <linux-arm-msm@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <quic_mmanikan@...cinc.com>, <quic_srichara@...cinc.com>,
        <quic_varada@...cinc.com>, <robin.murphy@....com>,
        <u.kleine-koenig@...libre.com>, <martin.petersen@...cle.com>,
        <fenghua.yu@...el.com>, <av2082000@...il.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] dmaengine: qcom: bam_dma: Avoid writing unavailable
 register



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@...cinc.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 am checking this will fix and post patch quickly.
> 
>>
>> [..]
>>
>>>    	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
>