linux-kernel - Re: [PATCH] dmaengine: qcom: bam_dma: Avoid accessing BAM

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Message-ID: <0892dca2-e76b-4aab-95cf-7437dabfc7a4@kernel.org>
Date: Sat, 8 Feb 2025 14:42:20 +0200
From: Georgi Djakov <djakov@...nel.org>
To: Bjorn Andersson <bjorn.andersson@....qualcomm.com>,
 Vinod Koul <vkoul@...nel.org>, Md Sadre Alam <quic_mdalam@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
 linux-kernel@...r.kernel.org, Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH] dmaengine: qcom: bam_dma: Avoid accessing BAM_REVISION on
 remote BAM

On 7.02.25 22:17, Bjorn Andersson wrote:
> Commit '57a7138d0627 ("dmaengine: qcom: bam_dma: Avoid writing
> unavailable register")' made this read unconditional, in order to
> identify if the instance is BAM-NDP or BAM-Lite.
> But the BAM_REVISION register is not accessible on remotely managed BAM
> instances and attempts to access it causes the system to crash.
> 
> Move the access back to be conditional and expand the checks that was
> introduced to restore the old behavior when no revision information is
> available.
> 
> Fixes: 57a7138d0627 ("dmaengine: qcom: bam_dma: Avoid writing unavailable register")
> Reported-by: Georgi Djakov <djakov@...nel.org>
> Closes: https://lore.kernel.org/lkml/9ef3daa8-cdb1-49f2-8d19-a72d6210ff3a@kernel.org/
> Signed-off-by: Bjorn Andersson <bjorn.andersson@....qualcomm.com>

Tested-by: Georgi Djakov <djakov@...nel.org> # db845c

Thanks,
Georgi