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. The Changes have been tested on the Tegra234 platform. Vidya Sagar (4): dt-bindings: Add "hotplug-gpios" PCIe property PCI/hotplug: Add GPIO PCIe hotplug driver PCI: tegra194: Add support to configure a pluggable slot PCI: tegra194: Enable GPIO based Hot-Plug support Documentation/devicetree/bindings/pci/pci.txt | 4 + drivers/pci/controller/dwc/pcie-tegra194.c | 85 +++++++- drivers/pci/hotplug/Kconfig | 11 + drivers/pci/hotplug/Makefile | 1 + drivers/pci/hotplug/gpio_php.c | 200 ++++++++++++++++++ drivers/pci/hotplug/gpiophp.h | 40 ++++ 6 files changed, 334 insertions(+), 7 deletions(-) create mode 100644 drivers/pci/hotplug/gpio_php.c create mode 100644 drivers/pci/hotplug/gpiophp.h -- 2.17.1
