linux-kernel - Re: [PATCH v4 1/7] dma: qcom: bam_dma: Fix command element mask field for BAM v1.6.0+

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Message-ID: <e0556d38-249f-d8ef-ab91-d5dd3a528d5c@quicinc.com>
Date: Tue, 10 Feb 2026 15:14:40 +0530
From: Md Sadre Alam <quic_mdalam@...cinc.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, <andersson@...nel.org>,
        <konradybcio@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
        <conor+dt@...nel.org>, <vkoul@...nel.org>, <Frank.Li@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <dmaengine@...r.kernel.org>
CC: <quic_varada@...cinc.com>
Subject: Re: [PATCH v4 1/7] dma: qcom: bam_dma: Fix command element mask field
 for BAM v1.6.0+

Hi,

On 2/9/2026 5:36 PM, Krzysztof Kozlowski wrote:
> On 09/02/2026 12:43, Md Sadre Alam wrote:
>>>> that use BAM v1.6.0+, because the current code sets mask=0xffffffff
>>>> for all commands. For read commands on newer BAM versions, this results
>>>> in the hardware interpreting the destination address as 0xf_xxxxxxxx
>>>> (invalid high memory) instead of the intended 0x0_xxxxxxxx address.
>>>>
>>>> Fixed this issue by:
>>>> 1. Updating the bam_cmd_element structure documentation to reflect the
>>>>      dual purpose of the mask field
>>>> 2. Modifying bam_prep_ce_le32() to set appropriate mask values based on
>>>>      command type:
>>>>      - For read commands: mask = 0 (32-bit addressing, upper bits = 0)
>>>>      - For write commands: mask = 0xffffffff (traditional write mask)
>>>> 3. Maintaining backward compatibility with older BAM versions
>>>>
>>>> This fix enables proper NAND functionality on IPQ5424 and other platforms
>>>> using BAM v1.6.0+ while preserving compatibility with existing systems.
>>>
>>> Fixes tag? CC-stable?
>>
>> This patch is not fixing an existing commit. This is to address the
>> update in the newer version of the hardware.
> 
> Then "this fix" is misleading. Either you fix or not fix.
You are right — the wording is misleading. I will update the commit 
message in next revision.

Thanks,
Alam.