On Sat, Oct 01, 2022 at 12:57:43AM +0530, Vidya Sagar wrote: > To support the Hot-plug feature, PCIe spec has a well-defined model for > hardware implementation and software programming interface. There are also > some architectures/platforms where the Hot-plug feature is implemented in a > non-standard way and software support for the respective implementations is > available with the kernel. This patch series attempts to add support for one > such non-standard way of supporting the Hot-plug feature where a single GPIO > is used to detect and report the Hot-Plug and Unplug events to the SW. > The platforms that can use this piece of software need to have GPIO routed > from the slot to the controller which can indicate the presence/absence of > the downstream device through its state. This GPIO should also have the > capability to interrupt the system when the connection/disconnection event > takes place. > A GPIO Hot-plug framework is written which looks for a "hotplug-gpios" named > GPIO entry in the corresponding device-tree entry of the controller and > registers a hot-pluggable slot with the Hot-plug framework. > The platform drivers of the PCIe host bridges/root ports can register with the > aforementioned GPIO Hot-Plug framework along with ops to perform any platform > specific tasks during Hot-Plug/Unplug events. > > Oza Pawandeep made an attempt to upstream support for a similar Hot-plug > feature implementation at a platform level, but the implementation as such > was very specific to that platform (at least the way I understood it). > https://patchwork.kernel.org/project/linux-pci/patch/1504155029-24729-2-git-send-email-oza.oza@xxxxxxxxxxxx/ > https://patchwork.kernel.org/project/linux-pci/patch/1504155029-24729-3-git-send-email-oza.oza@xxxxxxxxxxxx/ > https://patchwork.kernel.org/project/linux-pci/patch/1504155029-24729-4-git-send-email-oza.oza@xxxxxxxxxxxx/ > This current series also attempts to address that by extracting out all the > common code to do with GPIO and Hot-plug core framework and expecting the > platform drivers to only register/unregister with the GPIO framework. So, > @Oza, could you try using the GPIO framework from this series and enable > Hot-plug support for your platform if it still makes sense? > > @Rob, > Regarding the DT documentation change to add about 'hotplug-gpios, I'm not > sure if pci.txt is the right place or the dt-schema repository > i.e https://github.com/devicetree-org/dt-schema > But, in the interest of keeping all the changes related to this feature in the > the same repository, I made the changes to the pci.txt file in this repo itself. > Please let me know if the documentation change needs to be moved to the other > repo. Nothing should be added to pci.txt. So yes, dt-schema is where this needs to end up. Rob
