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Tue, 29 Aug 2023 09:47:42 -0700 (PDT) Received: from [192.168.0.22] ([77.252.47.196]) by smtp.gmail.com with ESMTPSA id f15-20020aa7d84f000000b0052228721f84sm5881691eds.77.2023.08.29.09.47.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Aug 2023 09:47:42 -0700 (PDT) Message-ID: <86bb50fd-72f3-7c76-c4fe-f8e4765e33d5@linaro.org> Date: Tue, 29 Aug 2023 18:47:40 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [PATCH 06/11] firmware: qcom-shm-bridge: new driver Content-Language: en-US To: Bartosz Golaszewski Cc: Andy Gross , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Catalin Marinas , Will Deacon , Arnd Bergmann , Alex Elder , Srini Kandagatla , kernel@quicinc.com, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20230828192507.117334-1-bartosz.golaszewski@linaro.org> <20230828192507.117334-7-bartosz.golaszewski@linaro.org> <8b7bada9-3898-1b60-3dea-766a760412f7@linaro.org> From: Krzysztof Kozlowski In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230829_094748_776759_DE9569EB X-CRM114-Status: GOOD ( 22.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 29/08/2023 15:24, Bartosz Golaszewski wrote: >>> +phys_addr_t qcom_shm_bridge_to_phys_addr(void *vaddr) >>> +{ >>> + struct qcom_shm_bridge_chunk *chunk; >>> + struct qcom_shm_bridge_pool *pool; >>> + >>> + guard(spinlock_irqsave)(&qcom_shm_bridge_chunks_lock); >>> + >>> + chunk = radix_tree_lookup(&qcom_shm_bridge_chunks, >>> + (unsigned long)vaddr); >>> + if (!chunk) >>> + return 0; >>> + >>> + pool = chunk->parent; >>> + >>> + guard(spinlock_irqsave)(&pool->lock); >> >> Why both locks are spinlocks? The locks are used quite a lot. > > I'm not sure what to answer. The first one protects the global chunk > mapping stored in the radix tree. The second one protects a single > memory pool from concurrent access. Both can be modified from any > context, hence spinlocks. Not much PREEMPT friendly, although indeed protected code is small. At least here, I did not check other places. > >> >>> + >>> + return gen_pool_virt_to_phys(pool->genpool, (unsigned long)vaddr); >>> +} >>> +EXPORT_SYMBOL_GPL(qcom_shm_bridge_to_phys_addr); >>> + >>> +static int qcom_shm_bridge_probe(struct platform_device *pdev) >>> +{ >>> + struct qcom_shm_bridge_pool *default_pool; >>> + struct device *dev = &pdev->dev; >>> + int ret; >>> + >>> + /* >>> + * We need to wait for the SCM device to be created and bound to the >>> + * SCM driver. >>> + */ >>> + if (!qcom_scm_is_available()) >>> + return -EPROBE_DEFER; >> >> I think we miss here (and in all other drivers) device links to qcm. >> > > Well, SCM, once probed, cannot be unbound. What would device links > guarantee above that? Runtime PM, probe ordering (dependencies) detection. > >>> + >>> + ret = qcom_scm_enable_shm_bridge(); >>> + if (ret) >>> + return dev_err_probe(dev, ret, >>> + "Failed to enable the SHM bridge\n"); >>> + >>> + default_pool = qcom_shm_bridge_pool_new_for_dev( >>> + dev, qcom_shm_bridge_default_pool_size); >>> + if (IS_ERR(default_pool)) >>> + return dev_err_probe(dev, PTR_ERR(default_pool), >>> + "Failed to create the default SHM Bridge pool\n"); >>> + >>> + WRITE_ONCE(qcom_shm_bridge_default_pool, default_pool); >>> + >>> + return 0; >>> +} >>> + >>> +static const struct of_device_id qcom_shm_bridge_of_match[] = { >>> + { .compatible = "qcom,shm-bridge", }, >>> + { } >>> +}; >>> + >>> +static struct platform_driver qcom_shm_bridge_driver = { >>> + .driver = { >>> + .name = "qcom-shm-bridge", >>> + .of_match_table = qcom_shm_bridge_of_match, >>> + /* >>> + * Once enabled, the SHM Bridge feature cannot be disabled so >>> + * there's no reason to ever unbind the driver. >>> + */ >>> + .suppress_bind_attrs = true, >>> + }, >>> + .probe = qcom_shm_bridge_probe, >>> +}; >>> + >>> +static int __init qcom_shm_bridge_init(void) >>> +{ >>> + return platform_driver_register(&qcom_shm_bridge_driver); >>> +} >>> +subsys_initcall(qcom_shm_bridge_init); >> >> Why this is part of subsystem? Should be rather device_initcall... or >> simply module (and a tristate). >> > > We want it to get up as soon as possible (right after SCM, because SCM > is the first user). Then probably should be populated/spawned by SCM. Best regards, Krzysztof _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel