On Fri, May 31, 2024 at 03:47:24PM -0700, Mayank Rana wrote: > Hi Rob / Mani > > On 4/15/2024 4:30 PM, Mayank Rana wrote: > > Hi Rob > > > > Excuse me for late response on this (was OOO). > > On 4/10/2024 9:58 AM, Rob Herring wrote: > > > On Mon, Apr 08, 2024 at 11:57:58AM -0700, Mayank Rana wrote: > > > > Hi Mani > > > > > > > > On 4/5/2024 9:17 PM, Manivannan Sadhasivam wrote: > > > > > On Fri, Apr 05, 2024 at 10:41:15AM -0700, Mayank Rana wrote: > > > > > > Hi Mani > > > > > > > > > > > > On 4/4/2024 10:30 PM, Manivannan Sadhasivam wrote: > > > > > > > On Thu, Apr 04, 2024 at 12:11:24PM -0700, Mayank Rana wrote: > > > > > > > > On some of Qualcomm platform, firmware > > > > > > > > configures PCIe controller into > > > > > > > > ECAM mode allowing static memory allocation for > > > > > > > > configuration space of > > > > > > > > supported bus range. Firmware also takes care of > > > > > > > > bringing up PCIe PHY > > > > > > > > and performing required operation to bring PCIe > > > > > > > > link into D0. Firmware > > > > > > > > also manages system resources (e.g. > > > > > > > > clocks/regulators/resets/ bus voting). > > > > > > > > Hence add Qualcomm PCIe ECAM root complex driver > > > > > > > > which enumerates PCIe > > > > > > > > root complex and connected PCIe devices. > > > > > > > > Firmware won't be enumerating > > > > > > > > or powering up PCIe root complex until this > > > > > > > > driver invokes power domain > > > > > > > > based notification to bring PCIe link into D0/D3cold mode. > > > > > > > > > > > > > > > > > > > > > > Is this an in-house PCIe IP of Qualcomm or the same > > > > > > > DWC IP that is used in other > > > > > > > SoCs? > > > > > > > > > > > > > > - Mani > > > > > > Driver is validated on SA8775p-ride platform using PCIe DWC IP for > > > > > > now.Although this driver doesn't need to know used PCIe > > > > > > controller and PHY > > > > > > IP as well programming sequence as that would be taken > > > > > > care by firmware. > > > > > > > > > > > > > > > > Ok, so it is the same IP but firmware is controlling the > > > > > resources now. This > > > > > information should be present in the commit message. > > > > > > > > > > Btw, there is an existing generic ECAM host controller driver: > > > > > drivers/pci/controller/pci-host-generic.c > > > > > > > > > > This driver is already being used by several vendors as > > > > > well. So we should try > > > > > to extend it for Qcom usecase also. > > > > > > I would take it a bit further and say if you need your own driver, then > > > just use the default QCom driver. Perhaps extend it to support ECAM. > > > Better yet, copy your firmware setup and always configure the QCom h/w > > > to use ECAM. > > Good suggestion. Although here we are having 2 set of requirements: > > 1. ECAM configuration > > 2. Managing PCIe controller and PHY resources and programming from > > firmware as well > > Hence it is not feasible to use default QCOM driver. > > > If you want to extend the generic driver, that's fine, but we don't need > > > a 3rd. > > I did consider this part before coming up with new driver. Although I > > felt that > > below mentioned functionality may not look more generic to be part of > > pci-host-generic.c driver. > > > > I did review pci-host-generic.c driver for usage. although there > > > > are more > > > > functionalityneeded for use case purpose as below: > > > > 1. MSI functionality > > > > > > Pretty sure the generic driver already supports that. > > I don't find any MSI support with pci-host-generic.c driver. > > > > 2. Suspend/Resume > > > > > > Others might want that to work as well. > > Others firmware won't have way to handle D3cold and D0 functionality > > handling as > > needed here for supporting suspend/resume as I don't find any interface > > for pci-host-generic.c driver to notify firmware. here we are having way > > to talk to firmware using GenPD based power domain usage to communicate > > with firmware. > > > > > > 3. Wakeup Functionality (not part of current change, but would be added > > > > later) > > > > > > Others might want that to work as well. > > possible if suspend/resume support is available or used. > > > > 4. Here this driver provides way to virtualized PCIe controller. > > > > So VMs only > > > > talk to a generic ECAM whereas HW is only directed accessed by > > > > service VM. > > > > > > That's the existing driver. If if doesn't work for a VM, fix the VM. > > Correct. > > > > 5. Adding more Auto based safety use cases related implementation > > > > > > Now that's just hand waving. > > Here I am trying to provide new set of changes plan to be added as part > > of required functionality. > > > > > > Hence keeping pci-host-generic.c as generic driver where above > > > > functionality > > > > may not be needed. > > > > > > Duplicating things to avoid touching existing drivers is not how kernel > > > development works. > > I shall try your suggestion and see how it looks in terms of code > > changes. Perhaps then we can have more clarity in terms of adding more > > functionality into generic or having separate driver. > I just learnt that previously dwc related PCIe ECAM driver and MSI > controller driver tried out as: > > https://lore.kernel.org/linux-pci/20170821192907.8695-1-ard.biesheuvel@xxxxxxxxxx/ > > Although there were few concerns at that time. Due to that having dwc > specific MSI functionality based driver was dropped, and pci-host-generic.c > driver is being updated using with dwc/snps specific ECAM operation. > > In current discussion, it seems that we are discussing to have identical > approach here. > > Atleast on Qualcomm SA8775p platform, I don't have any other way to support > MSI functionality i.e. extended SPI or ITS/LPI based MSI or using GICv2m > functionality are not supported. > > I don't see any other approach other than MSI based implementation within > pci-host-generic.c driver for dwc/snps based MSI controller. > > Do you have any suggestion on this ? > Since this ECAM driver is going to be used in newer Qcom SoCs, why can't you use GICv3 for MSI handling? - Mani -- மணிவண்ணன் சதாசிவம்
