linux-kernel - Re: [PATCH v2] dmaengine: qcom: bam_dma: allow omitting num-{channels,ees}

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ZG20Q3GFxIO+SQ9d@matsya>
Date:   Wed, 24 May 2023 12:22:51 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bhupesh Sharma <bhupesh.sharma@...aro.org>
Subject: Re: [PATCH v2] dmaengine: qcom: bam_dma: allow omitting
 num-{channels,ees}

On 19-05-23, 13:00, Stephan Gerhold wrote:
> The bam_dma driver needs to know the number of channels and execution
> environments (EEs) at probe time. If we are in full control of the BAM
> controller this information can be obtained from the BAM identification
> registers (BAM_REVISION/BAM_NUM_PIPES).
> 
> When the BAM is "controlled remotely" it is more complicated. The BAM
> might not be on at probe time, so reading the registers could fail.
> This is why the information must be added to the device tree in this
> case, using "num-channels" and "qcom,num-ees".
> 
> However, there are also some BAM instances that are initialized by
> something else but we still have a clock that allows to turn it on when
> needed. This can be set up in the DT with "qcom,controlled-remotely"
> and "clocks" and is already supported by the bam_dma driver. Examples
> for this are the typical BLSP BAM instances on older SoCs, QPIC BAM
> (for NAND) and the crypto BAM on some SoCs.
> 
> In this case, there is no need to read "num-channels" and
> "qcom,num-ees" from the DT. The BAN can be turned on using the clock
> so we can just read it from the BAM registers like in the normal case.
> 
> Check for the BAM clock earlier and skip reading "num-channels" and
> "qcom,num-ees" if it is present to allow simplifying the DT description
> a bit.

Applied, thanks

-- 
~Vinod