On 08/18/2016 07:25 AM, Kishon Vijay Abraham I wrote: > Hi, > > On Wednesday 17 August 2016 03:19 PM, Mingkai Hu wrote: >> >>> -----Original Message----- >>> From: Kishon Vijay Abraham I [mailto:kishon@xxxxxx] >>> Sent: Thursday, August 04, 2016 6:02 PM >>> To: Joao Pinto <Joao.Pinto@xxxxxxxxxxxx>; bhelgaas@xxxxxxxxxx; linux- >>> pci@xxxxxxxxxxxxxxx; arnd@xxxxxxxx; Jingoo Han <jingoohan1@xxxxxxxxx>; >>> Pratyush Anand <pratyush.anand@xxxxxxxxx> >>> Cc: Ley Foon Tan <lftan@xxxxxxxxxx>; Rob Herring <robh@xxxxxxxxxx>; >>> Tanmay Inamdar <tinamdar@xxxxxxx>; Roy Zang <tie- >>> fei.zang@xxxxxxxxxxxxx>; Mingkai Hu <mingkai.hu@xxxxxxxxxxxxx>; >>> Minghuan Lian <minghuan.Lian@xxxxxxxxxxxxx>; Richard Zhu >>> <Richard.Zhu@xxxxxxxxxxxxx>; Lucas Stach <l.stach@xxxxxxxxxxxxxx>; >>> Murali Karicheri <m-karicheri2@xxxxxx>; Thomas Petazzoni >>> <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>; Jason Cooper >>> <jason@xxxxxxxxxxxxxx>; Thierry Reding <thierry.reding@xxxxxxxxx>; >>> Simon Horman <horms@xxxxxxxxxxxx>; Zhou Wang >>> <wangzhou1@xxxxxxxxxxxxx>; Gabriele Paoloni >>> <gabriele.paoloni@xxxxxxxxxx>; Stanimir Varbanov <svarbanov@mm- >>> sol.com>; David Daney <david.daney@xxxxxxxxxx>; linux- >>> kernel@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux- >>> omap@xxxxxxxxxxxxxxx; Carlos Palminha >>> <CARLOS.PALMINHA@xxxxxxxxxxxx> >>> Subject: Re: Support for configurable PCIe endpoint >>> >>> Hi, >>> >>> On Wednesday 03 August 2016 07:09 PM, Joao Pinto wrote: >>>> Hi Kishon, >>>> >>>> On 8/3/2016 7:03 AM, 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. >>>>> >>>>> *) Modify platform driver to support EP mode (in my case pci-dra7xx.c). >>>>> >>>>> *) dt binding specific to EP mode should be created. >>>>> >>>>> Once I complete the implementation and start posting RFC patches, a >>>>> lot of these will become clear. But I want to check if this sounds >>>>> okay to you guys before starting the implementation. >>>>> >>>>> Let me know if you have some other ideas too. >>>>> >>>>> Cheers >>>>> Kishon >>>>> >>>>> [1] -> http://www.spinics.net/lists/linux-pci/msg26026.html >>>>> >>>> You are rising a topic that we are also addressing in Synopsys. >>>> >>>> For the PCIe RC hardware validation we are currently using the >>>> standard pcie-designware and pcie-designware-plat drivers. >>>> >>>> For the Endpoint we have to use an internal software package. Its main >>>> purpose is to initialize the IP registers, eDMA channels and make data >>>> transfer to prove that the everything is working properly. This is >>>> done in 2 levels, a custom driver built and loaded and an application >>>> that makes some ioctl to the driver executing some interesting >>>> functions to check the Endpoint status and make some data exchange. >>> hmm.. the platform I have doesn't have a DMA in PCIe IP >>> (http://www.ti.com/lit/ug/spruhz6g/spruhz6g.pdf). So in your testing does >>> the EP access RC memory? i.e the driver in the RC allocates memory from it's >>> DDR and gives it's DDR address to the EP. The EP then transfers data to this >>> address. (This is a typical use case with ethernet PCIe cards). IIUC that's not >>> simple with configurable EPs. I'd like to know more about your testing though. >>> >> Hi Kishon, >> >> This is a typical user case for EP to use DMA transfer data to/from RC memory. >> In our case, we implement ring (like BD ring) or register in EP to communicate >> The address allocated in RC memory, then EP can transfer data to/from RC memory. > Initially I had some confusion w.r.t this because the address allocated in RC > memory can also be an address in EP system. For example let's assume we connect > two similar systems one configured as RC and the other configured as EP. The > PCI driver in the RC allocates memory in it's DDR (say 0x80000000) and programs > this address in the EP. Since it's a similar system, 0x80000000 will also be an > address in the EPs DDR. This will result in EP transferring data to it's own > DDR (at 0x80000000) instead of the same address in RC. > > But later realized instead of directly using the DDR address given by RC, this > address should only be used to program the outbound window. That way the target > of the outbound window can be an address given by the RC and source should be > an address from the address space in the EP's system. > > Do you also use the RC memory address to program the outbound window? > When EP access RC memory, from EP perspective, there should be a offset added to 0x800000000 to match the pcie outbound access window. Thanks. Roy -- 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
