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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Loic Poulain , Sergey Ryazanov , Johannes Berg , linux-arm-msm@vger.kernel.org, netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Deepak Kumar Singh Subject: Re: [PATCH net-next v2 0/2] net: wwan: qcom_bam_dmux: Add restricted DMA pool support Message-ID: References: <20260920-qcom-bam-dmux-vmid-ext-v2-0-ef5ca2178378@oss.qualcomm.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Sep 28, 2026 at 04:02:47PM +0530, Vishnu Santhosh wrote: > On 20-09-2026 08:32 am, Vishnu Santhosh wrote: > > Some Qualcomm SoCs, such as Shikra, run the modem in a separate security > > domain with restricted access to system memory. BAM-DMUX DMA mappings > > and BAM descriptor FIFOs must therefore be constrained to a designated > > memory region that can be shared with the modem. Accesses outside that > > region can trigger an XPU violation. > > > > Add memory-region and qcom,vmid properties to the BAM-DMUX binding. > > When qcom,vmid is present, the driver SCM-assigns the entire restricted > > DMA pool to the local and remote execution environments before requesting > > the DMA channels. > > > > The restricted pool then contains the BAM-DMUX mappings. When the BAM DMA > > controller references the same pool, its descriptor FIFOs are covered by > > the assignment as well. > > > > A related binding change allows the BAM DMA controller to use the same > > restricted pool for descriptor FIFO allocations: > > > > https://lore.kernel.org/all/20260920-qcom-bam-dma-vmid-ext-v2-1-4dbbff0e57c8@oss.qualcomm.com/ > > ("dt-bindings: dma: qcom,bam-dma: Allow memory-region property") > > > > Signed-off-by: Vishnu Santhosh > > --- > > Changes in v2: > > - Replace the Shikra-specific compatible and coherent RX allocation with > > memory-region and qcom,vmid properties. > > - Use a restricted DMA pool for BAM-DMUX mappings and BAM descriptor FIFOs. > > - SCM-assign the complete pool before requesting the DMA channels. > > - Validate the remote VMID and restricted DMA pool configuration. > > - Link to v1: https://lore.kernel.org/r/20260714-qcom-bam-dmux-vmid-ext-v1-0-3f29da7cca76@oss.qualcomm.com > > > > --- > > Vishnu Santhosh (2): > > dt-bindings: net: qcom,bam-dmux: Add memory-region and qcom,vmid properties > > net: wwan: qcom_bam_dmux: Assign restricted DMA pool to remote processor > > > > .../devicetree/bindings/net/qcom,bam-dmux.yaml | 38 +++++++++ > > drivers/net/wwan/Kconfig | 1 + > > drivers/net/wwan/qcom_bam_dmux.c | 95 ++++++++++++++++++++++ > > 3 files changed, 134 insertions(+) > > --- > > base-commit: 8830e65ed46de41f849eefb8ba227d4852c460f6 > > change-id: 20260714-qcom-bam-dmux-vmid-ext-d9289db310c1 > > > > Best regards, > > Hi Stephan, > > I followed your suggestion and updated v2 to use the restricted DMA pool. > > Please let me know if this approach and the implementation look reasonable and > meets your expectations. > Thanks, the approach looks good to me. You received some comments from others and Sashiko already, so I will make a more thorough review from my side once you have addressed (or at least considered) them for v3. Thanks, Stephan