Hello, During the review of the patch that fixes DBI access in PCI EP, Rob suggested [1] using a fixed interface for passing the events from EPC to EPF instead of the in-kernel notifiers. This series introduces a simple callback based mechanism for passing the events from EPC to EPF. This interface is chosen for satisfying the below requirements: 1. The notification has to reach the EPF drivers without any additional latency. 2. The context of the caller (EPC) needs to be preserved while passing the notifications. With the existing notifier mechanism, the 1st case can be satisfied since notifiers aren't adding any huge overhead. But the 2nd case is clearly not satisfied, because the current atomic notifiers forces the EPF notification context to be atomic even though the caller (EPC) may not be in atomic context. In the notification function, the EPF drivers are required to call several EPC APIs that might sleep and this triggers a sleeping in atomic bug during runtime. The above issue could be fixed by using a blocking notifier instead of atomic, but that proposal was not accepted either [2]. So instead of working around the issues within the notifiers, let's get rid of it and use the callback mechanism. NOTE: DRA7xx and TEGRA194 drivers are only compile tested. Testing this series on the real platforms is greatly appreciated. Thanks, Mani [1] https://lore.kernel.org/all/20220802072426.GA2494@thinkpad/T/#mfa3a5b3a9694798a562c36b228f595b6a571477d [2] https://lore.kernel.org/all/20220228055240.24774-1-manivannan.sadhasivam@xxxxxxxxxx Changes in v5: * Collected review tag from Vidya * Fixed the issue reported by Kbot regarding missing declaration Changes in v4: * Added check for the presence of event_ops before involing the callbacks (Kishon) * Added return with IRQ_WAKE_THREAD when link_up event is found in the hard irq handler of tegra194 driver (Vidya) * Collected review tags Changes in v3: * As Kishon spotted, fixed the DRA7xx driver and also the TEGRA194 driver to call the LINK_UP callback in threaded IRQ handler. Changes in v2: * Introduced a new "list_lock" for protecting the epc->pci_epf list and used it in the callback mechanism. Manivannan Sadhasivam (5): PCI: dra7xx: Use threaded IRQ handler for "dra7xx-pcie-main" IRQ PCI: tegra194: Move dw_pcie_ep_linkup() to threaded IRQ handler PCI: endpoint: Use a separate lock for protecting epc->pci_epf list PCI: endpoint: Use callback mechanism for passing events from EPC to EPF PCI: endpoint: Use link_up() callback in place of LINK_UP notifier drivers/pci/controller/dwc/pci-dra7xx.c | 2 +- drivers/pci/controller/dwc/pcie-tegra194.c | 9 ++++- drivers/pci/endpoint/functions/pci-epf-test.c | 38 ++++++------------- drivers/pci/endpoint/pci-epc-core.c | 32 ++++++++++++---- include/linux/pci-epc.h | 10 +---- include/linux/pci-epf.h | 19 ++++++---- 6 files changed, 59 insertions(+), 51 deletions(-) -- 2.25.1
