On Tue, Aug 16, 2022 at 08:05:08PM +0530, Vidya Sagar wrote: > > > On 8/16/2022 7:45 PM, Lorenzo Pieralisi wrote: > > External email: Use caution opening links or attachments > > > > > > On Tue, Aug 02, 2022 at 07:37:38PM +0530, Manivannan Sadhasivam wrote: > > > On Tue, Aug 02, 2022 at 12:54:37PM +0530, Manivannan Sadhasivam wrote: > > > > On Mon, Aug 01, 2022 at 02:27:14PM -0600, Rob Herring wrote: > > > > > On Sat, Jul 30, 2022 at 8:50 AM Manivannan Sadhasivam > > > > > <manivannan.sadhasivam@xxxxxxxxxx> wrote: > > > > > > > > > > > > On Fri, Jul 29, 2022 at 05:44:04PM -0500, Bjorn Helgaas wrote: > > > > > > > [+cc Xiaowei (author of 6bfc9c3a2c70), Hou (author of 8bcca2658558)] > > > > > > > > > > > > > > On Thu, Jul 28, 2022 at 05:56:28PM +0530, Vidya Sagar wrote: > > > > > > > > On 7/28/2022 3:44 AM, Bjorn Helgaas wrote: > > > > > > > > > On Wed, Jun 22, 2022 at 09:31:33AM +0530, Vidya Sagar wrote: > > > > > > > > > > Platforms that cannot support their core initialization without the > > > > > > > > > > reference clock from the host, implement the feature 'core_init_notifier' > > > > > > > > > > to indicate the DesignWare sub-system about when their core is getting > > > > > > > > > > initialized. Any accesses to the core (Ex:- DBI) would result in system > > > > > > > > > > hang in such systems (Ex:- tegra194). This patch moves any access to the > > > > > > > > > > core to dw_pcie_ep_init_complete() API which is effectively called only > > > > > > > > > > after the core initialization. > > > > > > > > > > > > 6) What's going on with the CORE_INIT and LINK_UP notifiers? > > > > > > > dw_pcie_ep_init_notify() is only called by qcom and tegra. > > > > > > > dw_pcie_ep_linkup() is only called by dra7xx, qcom, and tegra. > > > > > > > As far as I can tell, nobody at all registers to handle those > > > > > > > events except a test. I think it's pointless to have that code > > > > > > > if nobody uses it. > > > > > > > > > > > > > > > > > > > I have submitted an actual driver that makes use of these notifiers: > > > > > > https://lore.kernel.org/lkml/20220502060611.58987-9-manivannan.sadhasivam@xxxxxxxxxx/ > > > > > > > > > > Notifiers aren't the best interface in the kernel. I think they are > > > > > best used if there's no real linkage between the sender and receiver. > > > > > For an EPC and EPF that's a fixed interface, so define a proper > > > > > interface. > > > > > > > > > > > > > Fair point! The use of notifiers also suffer from an issue where the notifier > > > > chain in EPC is atomic but the EPF calls some of the functions like > > > > pci_epc_write_header() could potentially sleep. > > > > > > > > I'll try to come up with an interface. > > > > > > > > > > I thought about using a new set of callbacks that define the EPC events and > > > have the EPF drivers populate them during probe time. Like below, > > > > > > ``` > > > diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h > > > index e03c57129ed5..45247802d6f7 100644 > > > --- a/include/linux/pci-epf.h > > > +++ b/include/linux/pci-epf.h > > > @@ -74,6 +74,20 @@ struct pci_epf_ops { > > > struct config_group *group); > > > }; > > > > > > +/** > > > + * struct pci_epf_events - Callbacks for capturing the EPC events > > > + * @init_complete: Callback for the EPC initialization complete event > > > + * @link_up: Callback for the EPC link up event > > > + */ > > > +struct pci_epc_events { > > > + void (*init_complete)(struct pci_epf *epf); > > > + void (*link_up)(struct pci_epf *epf); > > > +}; > > > + > > > /** > > > * struct pci_epf_driver - represents the PCI EPF driver > > > * @probe: ops to perform when a new EPF device has been bound to the EPF driver > > > @@ -172,6 +186,7 @@ struct pci_epf { > > > unsigned int is_vf; > > > unsigned long vfunction_num_map; > > > struct list_head pci_vepf; > > > + struct pci_epc_events *events; > > > }; > > > > > > /** > > > ``` > > > > > > When each of the event is received by the EPC driver, it will use the EPC API > > > to call the relevant event callback for _each_ EPF. Like below: > > > > > > ``` > > > diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c > > > index 6ad9b38b63a9..4b0b30b91403 100644 > > > --- a/drivers/pci/endpoint/pci-epc-core.c > > > +++ b/drivers/pci/endpoint/pci-epc-core.c > > > @@ -724,10 +724,15 @@ EXPORT_SYMBOL_GPL(pci_epc_linkdown); > > > */ > > > void pci_epc_init_notify(struct pci_epc *epc) > > > { > > > + struct pci_epf *epf; > > > + > > > if (!epc || IS_ERR(epc)) > > > return; > > > > > > - blocking_notifier_call_chain(&epc->notifier, CORE_INIT, NULL); > > > + list_for_each_entry(epf, &epc->pci_epf, list) { > > > + if (epf->events->init_complete) > > > + epf->events->init_complete(epf); > > > + } > > > } > > > EXPORT_SYMBOL_GPL(pci_epc_init_notify); > > > ``` > > > > > > Does this look good to you? I can spin up an RFC series, but wanted to check the > > > interface design beforehand. > > > > I am resuming patch reviews, have you posted a follow up ? > > > > Just to understand where we are with this thread and start reviewing > > from there, I will update patchwork accordingly (you should add > > a Link: to this thread anyway in the new series). > > Manivannan posted a new patch set at > https://patchwork.kernel.org/project/linux-pci/list/?series=666818 to > address concerns with the notifier mechanism. > > I would be sending a follow-up patch for the current patch soon. > While posting the new revision, please move dw_pcie_edma_detect() and ep_init() to init_complete function. They also perform DBI access. Thanks, Mani > Thanks, > Vidya Sagar > > > > > Thanks, > > Lorenzo > > > > > Thanks, > > > Mani > > > > > > > Thanks, > > > > Mani > > > > > > > > > Rob > > > > > > > > -- > > > > மணிவண்ணன் சதாசிவம் > > > > > > -- > > > மணிவண்ணன் சதாசிவம் -- மணிவண்ணன் சதாசிவம்
