| Message ID | 542A36E9.9020205@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
Thanks Danielle, Yes, I can add this support (for PEX89xx devices) to this driver subsequently. I'd however first wait for review comments on the current code (with the devices it currently supports). Thanks & Best Regards, Rajat On Tue, Sep 30, 2014 at 2:46 AM, Danielle Costantino <danielle.costantino@gmail.com> wrote: > I have also been working on a driver (userspace) for the plx89xx devices, If > any of this code is useful in the development of the plx driver, feel free > to include it. > > #define PLX_CMD_LEN 4 > #define PLX_CMD_I2C_READ 0x04 > #define PLX_CMD_I2C_WRITE 0x03 > #define PLX_CMD2_MASK 0x0f > #define PLX_PORT_SEL_B1(port) (port >> 1) > #define PLX_PORT_SEL_B0(port) ((port & 1) << 7) > #define PLX_CMD3_EN_ALL_BYTES 0x3c > #define PLX_REG_MASK 0xffc > #define PLX_REGISTER_ADDR(addr) ((uint16_t)((addr & PLX_REG_MASK) >> 2)) > #define PLX_REGISTER_ADDR_CMD3(addr) ((uint8_t)((PLX_REGISTER_ADDR(addr) >> > 8) & 0x3)) > #define PLX_REGISTER_ADDR_CMD4(addr) ((uint8_t)(PLX_REGISTER_ADDR(addr) & > 0xff)) > > enum plx_station { > plx_station_0 = 0x0, > plx_station_1, > plx_station_2, > plx_station_3, > plx_station_4, > plx_station_5, > plx_nt_port_vt, // when bit 4 value is 0 > }; > > enum plx_port { > plx_port_0 = 0x0, > plx_port_1, > plx_port_2, > plx_port_3, > }; > > static int pcie_i2c_read(SMBusdev *client, uint32_t *data, > enum plx_station station, enum plx_port port, uint16_t addr) { > int err = 0; > uint8_t plx_read_i2c_data[PLX_CMD_LEN] = { > [0] = PLX_CMD_I2C_READ, > [1] = ((0x00) | (station << 1) | (PLX_PORT_SEL_B1(port))), > [2] = ((PLX_REGISTER_ADDR_CMD3(addr)) | (PLX_CMD3_EN_ALL_BYTES) | > (PLX_PORT_SEL_B0(port))), > [3] = (PLX_REGISTER_ADDR_CMD4(addr)), > }; > > } > > > On Mon, Sep 29, 2014 at 9:51 PM, Rajat Jain <rajatxjain@gmail.com> wrote: >> >> >> Signed-off-by: Rajat Jain <rajatxjain@gmail.com> >> Signed-off-by: Rajat Jain <rajatjain@juniper.net> >> Signed-off-by: Guenter Roeck <groeck@juniper.net> >> --- >> Documentation/PCI/pex8xxx_i2c.txt | 134 >> +++++++++++++++++++++++++++++++++++++ >> 1 file changed, 134 insertions(+) >> create mode 100644 Documentation/PCI/pex8xxx_i2c.txt >> >> diff --git a/Documentation/PCI/pex8xxx_i2c.txt >> b/Documentation/PCI/pex8xxx_i2c.txt >> new file mode 100644 >> index 0000000..9195242 >> --- /dev/null >> +++ b/Documentation/PCI/pex8xxx_i2c.txt >> @@ -0,0 +1,134 @@ >> >> +================================================================================ >> + The PEX8xxx I2C Interface driver >> + >> + Rajat Jain <rajatjain@juniper.net> - Sep 2014 >> >> +================================================================================ >> + >> +0. Why have an I2C interface to a PCIe switch? >> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> +Other than the regular PCI express interface, most modern PCIe switches >> (e.g. >> +from IDT and PLX) have an I2C based secondary interface. This interface >> allows >> +access to all the registers of the switch. Some of these registers may >> not even >> +be accessible over the regular PCI interface. Also, there are certain >> registers >> +that can be written to, using only the I2C interface and may only be >> read-only >> +using the PCI interface. >> + >> +This I2C interface is often used in designs involving these switches, and >> can >> +be used for a variety of use cases where the switch needs to be >> configured >> +independent of the PCI subsystem (and likely before PCI enumeration). >> Some >> +examples: >> + >> +* Dividing a PCIe switch into multiple "virtual" switches. Using this >> feature, >> + a switch could be connected to 2 root ports for instance, each managing >> its >> + own PCI hierarchy, and the traffic from one virtual switch does not >> leak into >> + another. >> + >> +* Managing Transparent / Non-transparent bridging, and changing them >> on-the-fly. >> + There are ports that can be converted into "Non-transparent" bridge >> ports. >> + Essentially this is used to create different domains (not visible to >> + software). In a dynamic distributed system, it may be desirable to >> change a >> + transparent bridge to non-transparent or vice versa, for example, to >> handle a >> + failover situation. >> + >> +* Buggy hardware / Bad EEPROM configuration. There may be cases where an >> errata >> + involving register writes need to be applied before enumerating over >> PCI. >> + Also these switches are typically attached to an EEPROM that is >> supposed to >> + initialize the switch. If that EEPROM is not present, or contains bad >> + initialization data, this I2C interface can be used to fix that. >> + >> +* Changing switch configuration on the fly. In a multi-homed or complex >> + distributed systemsystem, there may be a need to change the switch >> + configuration (eg. change the upstream port, or the port or lane >> + configuration etc) to address run time scenarios (CPU plug out etc). >> + >> +1. What devices does this driver support? >> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> +PEX8xxx represents a family of PCI Express switches from the vendor PLX. >> +(http://www.plxtech.com/products/expresslane/switches). Currently this >> driver >> +supports the following PLX switch devices: >> +PEX8614 >> +PEX8618 >> +PEX8713 >> + >> +2. What does this "PEX8xxx I2C Interface driver" do? >> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> +This driver is an I2C client driver that allows talking to the said >> PEX8XXX >> +PCIe switches over the I2C interface. In a nutshell, it currently >> provides: >> + >> +* API calls to read / write the PEX8xxx switch device. >> +* A sysfs interface, to read / write the PEX8xxx switch device. >> + >> +The API calls are self explanatory (all reads / writes are 32 bit wide, >> but >> +the argument "byte_mask" can be used to selectively mask out the bytes): >> + >> +int pex8xxx_read(struct i2c_client *client, u8 stn, u8 mode, u8 >> byte_mask, >> + u8 port, u32 reg, u32 *val); >> +int pex8xxx_write(struct i2c_client *client, u8 stn, u8 mode, u8 >> byte_mask, >> + u8 port, u32 reg, u32 val) >> + >> +The arguments correspond to the arguments as described in the Chapter 7 >> +"I2C/SMBus Slave Interface Operation" of the all the switch datasheets. >> >> +http://www.plxtech.com/products/expresslane/pex8614#technicaldocumentation >> >> +http://www.plxtech.com/products/expresslane/pex8618#technicaldocumentation >> >> +http://www.plxtech.com/products/expresslane/pex8713#technicaldocumentation >> + >> +The sysfs interface is described in the next section. >> + >> +3. The PEX8xxx I2C driver sysfs Interface >> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> +The sysfs interface allows to read / write / dump the registers of any >> given >> +port of the pex8xxx switch. Note that all reads / writes are 32 bit wide. >> For >> +all pex8xxx devices, the following sysfs attributes are provided by this >> driver >> +in the directory /sys/bus/i2c/drivers/pex8xxx/<i2c-client-device>/ >> + >> +* "port_num" (RW) - The port number whose registers are to be read / >> written. >> +* "reg_addr" (RW) - The register offset (within the port register space) >> that >> + is to be read / written. >> +* "reg_value"(RW) - When read, it gives the value of the register at >> offset >> + "reg_addr" in the port "port_num" of the switch. When >> + written, it writes the value to the same register. >> +* "port_config_regs" (RO) - A binary dump of the 4KB register address >> space of >> + the port "port_num". >> + >> +In addition, some devices (currently PEX8713) support and require >> additional >> +parameters, and hence these will appear for PEX8713 only currently: >> + >> +* "port_mode" (RW) - Denotes the port mode to use to talk to the switch. >> Valid >> + values are: "transparent" / "nt-link" / "nt-virtual" >> / >> + "dma". >> +* "port_stn" (RW) - Port Station number. >> + >> +Note all the attributes preserve their value unless explicitly changed. >> Thus if >> +port_num is set to 5, then all subsequent reads / writes will be directed >> to >> +that port unless the port_num attribute is explicitly changed. >> + >> +4. Examples using sysfs interface >> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> + >> +* Instantiate the device (refer >> "Documentation/i2c/instantiating-devices"). >> + Valid strings of device names for this driver are "pex8614", "pex8618" >> and >> + "pex8713". >> + Example (pex8614 at I2C address 0x38 on I2C bus 55): >> + echo pex8614 0x38 > /sys/bus/i2c/devices/i2c-55/new_device >> + >> +* Verify if device was instantiated: >> + cd /sys/bus/i2c/drivers/pex8xxx/55-0038 >> + cat name (should give pex8614) >> + >> +* Dump all registers of port number 4: >> + echo 4 > port_num >> + od -x port_config_regs >> + >> +* Get register values at offsets 0x230, 0x234, 0x238 of port number 1: >> + echo 1 > port_num >> + echo 0x230 > reg_addr >> + cat reg_value >> + echo 0x234 > reg_addr >> + cat reg_value >> + echo 0x238 > reg_addr >> + cat reg_value >> + >> +* Write value 0x101 at offset 0x530 of port number 5: >> + echo 5 > port_num >> + echo 0x530 > reg_addr >> + echo 0x101 > reg_value >> -- >> 1.7.9.5 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-i2c" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > -- > - Danielle Costantino -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/PCI/pex8xxx_i2c.txt b/Documentation/PCI/pex8xxx_i2c.txt new file mode 100644 index 0000000..9195242 --- /dev/null +++ b/Documentation/PCI/pex8xxx_i2c.txt @@ -0,0 +1,134 @@ +================================================================================ + The PEX8xxx I2C Interface driver + + Rajat Jain <rajatjain@juniper.net> - Sep 2014 +================================================================================ + +0. Why have an I2C interface to a PCIe switch? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Other than the regular PCI express interface, most modern PCIe switches (e.g. +from IDT and PLX) have an I2C based secondary interface. This interface allows +access to all the registers of the switch. Some of these registers may not even +be accessible over the regular PCI interface. Also, there are certain registers +that can be written to, using only the I2C interface and may only be read-only +using the PCI interface. + +This I2C interface is often used in designs involving these switches, and can +be used for a variety of use cases where the switch needs to be configured +independent of the PCI subsystem (and likely before PCI enumeration). Some +examples: + +* Dividing a PCIe switch into multiple "virtual" switches. Using this feature, + a switch could be connected to 2 root ports for instance, each managing its + own PCI hierarchy, and the traffic from one virtual switch does not leak into + another. + +* Managing Transparent / Non-transparent bridging, and changing them on-the-fly. + There are ports that can be converted into "Non-transparent" bridge ports. + Essentially this is used to create different domains (not visible to + software). In a dynamic distributed system, it may be desirable to change a + transparent bridge to non-transparent or vice versa, for example, to handle a + failover situation. + +* Buggy hardware / Bad EEPROM configuration. There may be cases where an errata + involving register writes need to be applied before enumerating over PCI. + Also these switches are typically attached to an EEPROM that is supposed to + initialize the switch. If that EEPROM is not present, or contains bad + initialization data, this I2C interface can be used to fix that. + +* Changing switch configuration on the fly. In a multi-homed or complex + distributed systemsystem, there may be a need to change the switch + configuration (eg. change the upstream port, or the port or lane + configuration etc) to address run time scenarios (CPU plug out etc). + +1. What devices does this driver support? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +PEX8xxx represents a family of PCI Express switches from the vendor PLX. +(http://www.plxtech.com/products/expresslane/switches). Currently this driver +supports the following PLX switch devices: +PEX8614 +PEX8618 +PEX8713 + +2. What does this "PEX8xxx I2C Interface driver" do? +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +This driver is an I2C client driver that allows talking to the said PEX8XXX +PCIe switches over the I2C interface. In a nutshell, it currently provides: + +* API calls to read / write the PEX8xxx switch device. +* A sysfs interface, to read / write the PEX8xxx switch device. + +The API calls are self explanatory (all reads / writes are 32 bit wide, but +the argument "byte_mask" can be used to selectively mask out the bytes): + +int pex8xxx_read(struct i2c_client *client, u8 stn, u8 mode, u8 byte_mask, + u8 port, u32 reg, u32 *val); +int pex8xxx_write(struct i2c_client *client, u8 stn, u8 mode, u8 byte_mask, + u8 port, u32 reg, u32 val) + +The arguments correspond to the arguments as described in the Chapter 7 +"I2C/SMBus Slave Interface Operation" of the all the switch datasheets. +http://www.plxtech.com/products/expresslane/pex8614#technicaldocumentation +http://www.plxtech.com/products/expresslane/pex8618#technicaldocumentation +http://www.plxtech.com/products/expresslane/pex8713#technicaldocumentation + +The sysfs interface is described in the next section. + +3. The PEX8xxx I2C driver sysfs Interface +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The sysfs interface allows to read / write / dump the registers of any given +port of the pex8xxx switch. Note that all reads / writes are 32 bit wide. For +all pex8xxx devices, the following sysfs attributes are provided by this driver +in the directory /sys/bus/i2c/drivers/pex8xxx/<i2c-client-device>/ + +* "port_num" (RW) - The port number whose registers are to be read / written. +* "reg_addr" (RW) - The register offset (within the port register space) that + is to be read / written. +* "reg_value"(RW) - When read, it gives the value of the register at offset + "reg_addr" in the port "port_num" of the switch. When + written, it writes the value to the same register. +* "port_config_regs" (RO) - A binary dump of the 4KB register address space of + the port "port_num". + +In addition, some devices (currently PEX8713) support and require additional +parameters, and hence these will appear for PEX8713 only currently: + +* "port_mode" (RW) - Denotes the port mode to use to talk to the switch. Valid + values are: "transparent" / "nt-link" / "nt-virtual" / + "dma". +* "port_stn" (RW) - Port Station number. + +Note all the attributes preserve their value unless explicitly changed. Thus if +port_num is set to 5, then all subsequent reads / writes will be directed to +that port unless the port_num attribute is explicitly changed. + +4. Examples using sysfs interface +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +* Instantiate the device (refer "Documentation/i2c/instantiating-devices"). + Valid strings of device names for this driver are "pex8614", "pex8618" and + "pex8713". + Example (pex8614 at I2C address 0x38 on I2C bus 55): + echo pex8614 0x38 > /sys/bus/i2c/devices/i2c-55/new_device + +* Verify if device was instantiated: + cd /sys/bus/i2c/drivers/pex8xxx/55-0038 + cat name (should give pex8614) + +* Dump all registers of port number 4: + echo 4 > port_num + od -x port_config_regs + +* Get register values at offsets 0x230, 0x234, 0x238 of port number 1: + echo 1 > port_num + echo 0x230 > reg_addr + cat reg_value + echo 0x234 > reg_addr + cat reg_value + echo 0x238 > reg_addr + cat reg_value + +* Write value 0x101 at offset 0x530 of port number 5: + echo 5 > port_num + echo 0x530 > reg_addr + echo 0x101 > reg_value