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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Alex Elder From: Esteban Urrutia Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH 0/3] SM8450 IPA support Message-ID: <3e70d77e-6bec-4e16-ae88-a4f5161f182e@proton.me> In-Reply-To: <8309e9c7-a110-478b-8cd4-c002070d2b4c@riscstar.com> References: <20260622-sm8450-ipa-v1-0-532f0299f96e@proton.me> <959db395-ae71-4a50-bd46-ac5add545a52@riscstar.com> <48c624c3-5408-4862-b4ec-9321ad279bf9@proton.me> <8309e9c7-a110-478b-8cd4-c002070d2b4c@riscstar.com> Feedback-ID: 147889766:user:proton X-Pm-Message-ID: 64bb24bdd771c804828a3d7e9d0320e06a799b4a Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 7/8/26 3:49 PM, Alex Elder wrote: > This was interesting to see. It's something I should probably > document better. Most everything maps to the downstream code, > but it's not always completely obvious how, because the upstream > driver has evolved substantially. On a personal note, I'm surprised to see someone not from Qualcomm maintaining this driver. It must be hard, so kudos. > This means that the SRAM size (ipa_mem_data->smem_size) should > possibly be defined in devicetree (as the IMEM address and size > now are). >=20 > The SMEM region is used for "IPA filter tables", and access to > it is shared between the AP and the modem. Unlike the other > (host) memory regions, the size used is *not* included in the > ipa_init_modem_driver_req message that communicates from the > AP to the modem where the regions are, and their sizes. >=20 > So it's possible that the size used must actually match what > is expected by both the AP and modem. If that is the case, > using the smaller size might have problems on whichever > platform (SM8450?) expects the larger one. >=20 > So I'm not sure whether using the smaller size for both > platforms is OK; someone from Qualcomm might be able to > answer that question. I actually went ahead and reviewed downstream device trees I found on GitHub (1) which contain both SM8450 and SM8475 device trees looking for the qcom,ipa-q6-smem-size property, which would correspond to the SRAM size, and to my surprise, this was set to 0x9000 for both SoCs. Most likely the commit I got the SRAM information from (2) never made it to production devices. With this clarified, I think it should be okay to keep things defined as they currently are. > I'll try to explain those things separately. Regarding this, I have a question: where would this be published? Thanks for taking the time to properly review my changes. I'll address the review when I can. (1) https://github.com/sm8450-mainline/fdt (2) https://github.com/LineageOS/android_kernel_qcom_sm8450-devicetrees/com= mit/477aab9e7479ff553c7a162ae74029170a2e8291.patch Regards, Esteban