On Wed, Aug 03, 2016 at 11:33:19AM +0530, Kishon Vijay Abraham I wrote: > Hi, > > The PCIe controller present in TI's DRA7 SoC is capable of operating either in > Root Complex mode or Endpoint mode. (It uses Synopsys Designware Core).I'd > assume most of the PCIe controllers on other platforms that use Designware core > should also be capable to operate in endpoint mode. But linux kernel right now > supports only RC mode. > > PCIe endpoint support discussion came up briefly before [1] but it was felt the > practical use case will find firmware more suitable and endpoint support in > kernel can be used only for validation or demo. I disagree. It's highly useful for rapid prototyping of hardware interfaces, and I've been looking into PCIe EP drivers for exactly that reason recently. Going a little offtopic: any good DRA7 eval boards you'd recommend to try for this purpose? We already have a EP driver in the tree: drivers/misc/spear13xx_pcie_gadget.c but as far as I can tell it doesn't really work at the moment. > Validation or demo is itself a valid use case in my opinion (consider something > similar to gadget zero for USB). There can be other use cases as well. The RC > can use the SoC with EP mode support as an accelerator to accomplish specific > task. Here RC gives data to the EP. The EP processes the data. The processing > can be done either in ARM itself or it can use other hardware accelerators > (like DSP, IVA-HD etc..) present in the EP system. If HW accelerator is used, > the linux kernel running in ARM can be used to accomplish other tasks. Once EP > mode support is added, I think more use cases will be added. That sounds useful as well. > >From the high level this should look _similar_ to the gadget framework of USB. > One difference from USB would be this should allow HW components (like DSP, PRU > etc.. and maybe even some peripheral) in the EP system to be used by RC system. Indeed. > So these are the high-level steps that I thought would be needed to add EP > support in linux. > *) move pcie-designware.c out of drivers/pci/host (maybe create a > drivers/pci/designware/ folder?). All users of pcie-designware.c should be > moved here. > This is in preparation for adding EP mode support to designware. I'd use a new drivers/pci/controller. Or maybe just skip the rename for now and see how this evolves. The rest of the plan sounds fine to me. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
