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<5a79d3a2-d090-645b-da69-524b7e7a4d90@nvidia.com> <51f7de26-579a-8b9e-4e79-f4eee923ab38@codeaurora.org> <3838f17a-2ac8-bf3f-f0b1-f69bbe17629c@nvidia.com> From: Jon Hunter Message-ID: <1687797a-93f1-7e5c-6060-01c12c070964@nvidia.com> Date: Thu, 24 May 2018 10:36:34 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL102.nvidia.com (172.18.146.10) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/05/18 08:04, Ulf Hansson wrote: ... >> Any reason why we could not add a 'boolean' argument to the API to indicate >> whether the new device should be linked? I think that I prefer the API >> handles it, but I can see there could be instances where drivers may wish to >> handle it themselves. > > Coming back to this question. Both Tegra XUSB and Qcom Camera use > case, would benefit from doing the linking themselves, as it needs > different PM domains to be powered on depending on the current use > case - as to avoid wasting power. > > However, I can understand that you prefer some simplicity over > optimizations, as you told us. Then, does it mean that you are > insisting on extending the APIs with a boolean for linking, or are you > fine with the driver to call device_link_add()? I am fine with the driver calling device_link_add(), but I just wonder if we will find a several drivers doing this and then we will end up doing this later anyway. The current API is called ... * genpd_dev_pm_attach_by_id() - Attach a device to one of its PM domain. * @dev: Device to attach. * @index: The index of the PM domain. This naming and description is a bit misleading, because really it is not attaching the device that is passed, but creating a new device to attach a PM domain to. So we should consider renaming and changing the description and indicate that users need to link the device. Finally, how is a PM domain attached via calling genpd_dev_pm_attach_by_id() detached? Cheers Jon -- nvpublic