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Date: Wed, 11 Dec 2013 23:28:36 +0530 From: Jagan Teki <jagannadh.teki@...il.com> To: Randy Dunlap <rdunlap@...radead.org> Cc: Jagannadha Sutradharudu Teki <jagannadha.sutradharudu-teki@...inx.com>, Bjorn Helgaas <bhelgaas@...gle.com>, Rob Landley <rob@...dley.net>, "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, linux-doc@...r.kernel.org, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jagannadha Sutradharudu Teki <jaganna@...inx.com> Subject: Re: [PATCH 2/2] Documentation: pci: Add pcie-howto.txt Hi Randy On Wed, Dec 11, 2013 at 11:02 PM, Randy Dunlap <rdunlap@...radead.org> wrote: > On 12/11/13 01:15, Jagannadha Sutradharudu Teki wrote: >> Added pcie-howto.txt for describing the information >> on PCI Express basics and Root Complex driver. >> >> Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@...inx.com> >> --- >> Documentation/PCI/00-INDEX | 2 + >> Documentation/PCI/pcie-howto.txt | 184 +++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 186 insertions(+) >> create mode 100644 Documentation/PCI/pcie-howto.txt >> >> diff --git a/Documentation/PCI/00-INDEX b/Documentation/PCI/00-INDEX >> index b8b7721..d61e7b9 100644 >> --- a/Documentation/PCI/00-INDEX >> +++ b/Documentation/PCI/00-INDEX >> @@ -6,6 +6,8 @@ pci-error-recovery.txt >> - Info on PCI error recovery >> MSI-HOWTO.txt >> - The Message Signaled Interrupts (MSI) Driver Guide HOWTO and FAQ >> +pcie-howto.txt >> + - A guide describing the PCI Express basics and Root Complex driver >> pcie-portbus-howto.txt >> - A guide describing the PCI Express Port Bus driver >> pcie-aer-howto.txt >> diff --git a/Documentation/PCI/pcie-howto.txt b/Documentation/PCI/pcie-howto.txt >> new file mode 100644 >> index 0000000..963cb75 >> --- /dev/null >> +++ b/Documentation/PCI/pcie-howto.txt >> @@ -0,0 +1,184 @@ >> + PCI Express HOWTO >> + Jagannadha Sutradharudu Teki <jagannadh.teki@...il.com> >> + 05/12/2013 >> + >> +1. About this guide >> + >> +This guide describes the basics of the PCI Express and provides > > Express bus and > >> +information on how Linux PCIe subsystem looks like and at last > > what the Linux and ends > >> +with brief description of PCI Host controller/Root complex driver > > with a brief > >> +along with some sample code. >> + >> +2. Basic terminology and conventions >> + >> +PCI Express is >> +- A high performance, IO interconnect for peripherals. > > ^drop comma > >> +- Low hardware design overhead compared to PCI, as it uses less pins. >> +- A serial point-to-point interconnect between two devices. >> +- Implements packet based protocol for data transfer. > > packet-based > >> +- Supports features like Advanced power management, Advanced error >> + reporting facility, and hot-plug. >> + _________ >> + | | >> + | CPU | >> + |_________| >> + | >> + ___________________|___________________________ >> + | | ________ >> + | ROOT COMPLEX | | | >> + | |--------| Memory | >> + | Switch Port Root port | |________| >> + |_______________________________________________| >> + | PCIe Bus0 >> + ____________________________|______________________________________ >> + | | | >> + ____ ______|______ | ____|____ >> + | | / \ __|__ | | >> + | EP |-----| SWITCH | | | | BRIDGE | >> + |____| \_____________/ | EP | | PCIe - | >> + | | |_____| | PCI/PCIe| >> + __|__ __|__ |_________| >> + | | | | | PCIe Bus1 >> + | EP | | EP | __________|________________ >> + |_____| |_____| | | >> + __|__ __|__ >> + | | | | >> + | EP | | EP | >> + |_____| |_____| >> + >> +Root Complex (RC) >> +Connects the CPU and memory subsystem to the PCIe fabric (A topology comprised of PCIe >> +nodes like Root Complex, Endpoint, Bridge or a Switch) >> + >> +Port >> +Interface between a PCIe component and the Link. >> + >> +Link >> +PCIe interconnect is referred as a Link, and connects two devices. >> + >> +Lane >> +A PCIe link consists of either 1, 2, 4, 8, 12, 16 or 32 signals in each direction >> +(each signal needs two wires - one for Tx and other for Rx). these signals are > > These > >> +referred to as Lanes. >> + >> +Upstream Port >> +Port that points in the direction of RC. >> + >> +Downstream Port >> +Port the points away from the RC. > > that > >> + >> +Root Port >> +Whose upstream port is RC and dowstream port should be a EP or Bridge. > > an > >> + >> +Switch Port >> +Whose upstream port is RC and dowstream port is always be a switch. > > always a switch. > >> + >> +Endpoint (EP) >> +Devices other than RC, Switches and Bridges which either generates or terminates a PCIe > > generate or terminate > >> +transaction. These are peripheral devices such as Ethernet, USB and graphics devices. >> + >> +Switch >> +PCIe device single upstream port as RC and multiple downstream ports as EP's, >> +Switches or Bridges. >> + >> +Bridge >> +Is for extending PCIe Bus segment - whose downstream port points to one more PCIe bus. >> + >> +3. Linux PCIe Subsystem >> + >> + ifconfig open()/close/read()/write() /proc, /sys >> + ^ ^ ^ ^ >> + | | | | >> + | | | | >> + | | | V >> + | | | PCIe Port Bus services >> + | | | (AER, HP, PME, VC >> + | | | drivers/pci/pcie/ >> + | | | drivers/pci/hotplug) >> + V V V ^ >> + Socket Block Char | >> + layer Subsystem Subsystem | >> + ^ ^ ^ | pcie_port_service_register() >> + | | | | >> + | | | | >> + V V V V >> + Common net USB Input PCIe Port Core >> + device layer Core Core (drivers/pci/pcie/portdrv_core.c) >> + ^ ^ ^ ^ >> + | | | | pcie_port_bus_register() >> + | | | | >> + _____V_____ ____V____ ____V_____ _________V___________ >> + | | | | | | | | >> + All these are | GEM | | USB HC | | Mouse/KB/| | PCIe Port Bus driver| >> + PCI endpoint | Controller| | driver | | TS HC | | (drivers/pci/pcie/ | >> + drivers | driver | | | | driver | | portdrv_pci.c) | >> + |___________| |_________| |__________| |_____________________| >> + ^ ^ ^ ^ >> + |__________ | | _________| >> + | | | | pci_register_driver() >> + ___________________ pci_bus_*() __V___V_____________V__________V______ >> + | | pci_scan_root_bus() | | >> + | PCI BIOS |-------------------->| PCI Core | >> + | (arch/arm/kernel/ |<--------------------| (drivers/pci/pci* | >> + ----->| bios32.c)) |<--- pcibios_*() | drivers/pci/bus.c) | >> + | |___________________| | |______________________________________| >> + | ^ | >> + | | | pci_common_init_dev() >> + | | | >> + ____V___ ____V___ ___V____ >> + | | | | | | >> + | Renesas| | Tergra | | Exynos | > > Tegra > >> + | PCI HC | | PCIe HC| | PCIe HC| drivers/pci/host/ >> + | driver | | driver | | driver | All these are >> + |________| |________| |________| PCI Root Complex drivers >> + | | | >> + | | | >> + V V V >> + platform_driver_register() >> + >> +Note: >> +Linux PCI subsystem is like above one without have a PCIe port bus stack. > > having > >> +For more details abou this block see http://jagannadhteki.blog.com/2013/12/04/linux-pcie-subsystem/ > > about > >> + >> +PCI HC/RC driver >> +- Low level initialization and configuration (board, soc) > > SOC or SoC, please > >> +- Invokes PCI-BIOS - for bus enumerations so-that the endpoints on bus is ready. > > so that are > >> +- Supplies struct pci_ops to read/write config space. >> +- Setup the resources like bus numbers, memory/IO space, Interrupt numbers, MSI. >> +- Register PCI-BIOS as pci_common_init_dev() >> + >> +PCI BIOS >> +- Architecture specific PCI >> +- Bus enumeration - Lane, Bus, Device, Memory, Interrupt. >> +- Enumeration ends up with scanning all endpoints on bus got discovered. > > ^^^ confusing > >> +- Register to PCI core for common accessing of endpoint drivers. >> +- pci_scan_root_bus() and pci_bus_*() >> + >> +PCI Core >> +- Provides services to Lower level BIOS and Upper level endpoint layers. >> +- Creates device entries for proc/sysfs information. >> +- Linux kernel pci bus and driver management code. > > PCI > >> +- Provides set of abstraction functions that endpoint drivers can used to > > use > >> + initiate pci communication with attached endpoints. > > PCI > >> +- Calls BIOS codes with pcibios_* >> + >> +PCI Endpoint driver >> +- Individual endpoint drivers from upper layer. >> +- Accessing config space upon respective endpoint enumeration done. >> +- Communicate over the endpoint for Tx/Rx transactions. >> +- Register to PCI core as pci_driver_register() >> + >> +PCIe Port Bus driver >> +- A logical PCI-PCI Bridge structure. >> +- Root Port and the Switch Port. >> +- See Documentation/PCI/pcie-busport-howto.txt > ~~~~~~~ > portbus > Thanks for your comments will send the next version after fixing these. -- Thanks, Jagan. -------- Jagannadha Sutradharudu Teki, E: jagannadh.teki@...il.com, P: +91-9676773388 Engineer - System Software Hacker U-boot - SPI Custodian and Zynq APSOC Ln: http://www.linkedin.com/in/jaganteki -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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