DSP eth offload driver

1. Offload driver can be enabled only on 1 interface. Limitation is documented.

2. More details on sharing other tasks with offload driver.

Offload task running on the offload processor handles all of EMAC HW programming, L3/L4 checksum computation and communication with the main Host processor(running Linux). To maximize throughput and minimize latency, the offload task is run as a minimum priority task that continuosly polls for packets to be sent and received. For some applications depending on more relaxed throughput and latency requirements it might be possible to use the offload processor for additional tasks. In this case, following changes need to be carried out

• Modify the ethernet offload task priority relative to other tasks in the system. For instance, if an audio codec needs to be run on the offload processor and remaining CPU cycles be used for offload process - set the priority of the audio codec task higher than that of offload task.
  • The offload task priority is set at the time of task creation in the ETH_OFFLOAD_Emac_TaskInit() function in "mcfw/src_bios6/eth_offload/bios6/src/eth_offload_emac.c" file. By default it is set to run as the lowest priority task in the system
• Modify the offload task to poll with a timeout instead of continuos polling.
  • In the driver open function "ETH_OFFLOAD_emacOpen()" in "mcfw/src_bios6/eth_offload/bios6/src/eth_offload_emac.c", the polling timeout is set to "0", thereby enabling continuos polling. For accomodating other tasks in the system, modify the timeout interval("pin->semPendTimeout=10") to a meaningful number in the open call. You can choose a larger or smaller interval depending on the throughput vs cpu cycle needed for the application

Hi Sivagamy,

Very thanks for quick and  the detailed reply.

Q1: 1. Offload driver can be enabled only on 1 interface. Limitation is documented.

Sorry! I know that only one EMAC can be offloaded currently.  My question:  only HW EMAC1 is supported? Because there are a large number of packets in HW EMAC2(eth0 in my system) in my usecase. Does offload driver can be enabled for HW EMAC2(eth0)? Is it hardware related?

Thanks!

I think it can be interchanged. You will have to rebuild kernel by changing "eth_offload" string in kernel code - arch/arm/mach-omap2/devices.c

Hi Sivagamy,

Thanks for your reply.

I have tried to modify kernel_code/arch/arm/mach-omap/devices.c

static struct platform_device ti816x_emac1_device = {
    .name    =    "davinci_emac",
    .id    =    0,
    .num_resources    =    ARRAY_SIZE(ti816x_emac1_resources),
    .resource    =    ti816x_emac1_resources,
};

static struct platform_device ti816x_emac2_device = {
    .name    =    "eth_offload",
    .id    =    1,
    .num_resources    =    ARRAY_SIZE(ti816x_emac2_resources),
    .resource    =    ti816x_emac2_resources,
};

eth0 : driver: TI DaVinci EMAC Linux v6.1

eth1 : driver: TI DSP Accelarated EMAC Linux v0

When I exchange the modifes to the following:

static struct platform_device ti816x_emac1_device = {
    .name    =    "eth_offload",
    .id    =    0,
    .num_resources    =    ARRAY_SIZE(ti816x_emac1_resources),
    .resource    =    ti816x_emac1_resources,
};

static struct platform_device ti816x_emac2_device = {
    .name    =    "davinci_emac",
    .id    =    1,
    .num_resources    =    ARRAY_SIZE(ti816x_emac2_resources),
    .resource    =    ti816x_emac2_resources,
};

why linux system eth0 and eth1 port in my board have be changed...and driver information is the same as below...

eth0 : driver: TI DaVinci EMAC Linux v6.1

eth1 : driver: TI DSP Accelarated EMAC Linux v0

Am I missing something?

Thanks again!

Hi

Your observations are correct and i will summarize once more

1) only one of the ethernet MAC instances can be managed by the offload driver. You can interchange the instance to be managed by modifying the platform device definitions as above

2) The device numbering "eth0" vs "eth1" is dependent on order in which the driver/device binding happens during linux initialization. This should not be confused with the id field in platform device structure. The id field is used internally when the same driver has to manage multiple instances of the same peripheral

It is most likely that in your case, the native ethernet driver completes its initialization first - and hence always gets recognized as eth0. You can cross-check your init console log(or paste it here for review)

The important part is , though the offload driver reports its instance as eth1 - on the board physically the interface being managed by the offload driver must have changed and you should verify that

Hope this helps.

Hi Srirama,

Very thanks for you help.

"The important part is , though the offload driver reports its instance as eth1 - on the board physically the interface being managed by the offload driver must have changed and you should verify that"

Yes, you are right.

Sorry! I am new for ethernet driver. Please help me check:

I dont know why the native ethernet driver always be initialized first and recognized as eth0.

In my board, there are two emac phys: phy address 0x03, 0x07,

phy address 0x03 <-> EMAC2 in DM8168

phy address 0x07 <-> EMAC1 in DM8168

I want phy:0x03 bind with interface eth0 and phy:0x07 with eth1. The following is some modifies in devices.c:

static struct emac_platform_data ti816x_emac1_pdata = {
    .rmii_en    =    0,
    .phy_id        =    "0:03",
    .gigabit_en    =    1,
};
static struct emac_platform_data ti816x_emac2_pdata = {
    .rmii_en    =    0,
    .phy_id        =    "0:07",
    .gigabit_en    =    1,
};

static struct resource ti816x_emac1_resources[] = {
    {
        .start    =    TI816X_EMAC2_BASE,
        .end    =    TI816X_EMAC2_BASE + 0x3FFF,
        .flags    =    IORESOURCE_MEM,
    },
    {
        .start    =    TI816X_IRQ_MACRXTHR1,
        .end    =    TI816X_IRQ_MACRXTHR1,
        .flags    =    IORESOURCE_IRQ,
    },
    {
        .start    =    TI816X_IRQ_MACRXINT1,
        .end    =    TI816X_IRQ_MACRXINT1,
        .flags    =    IORESOURCE_IRQ,
    },
    {
        .start    =    TI816X_IRQ_MACTXINT1,
        .end    =    TI816X_IRQ_MACTXINT1,
        .flags    =    IORESOURCE_IRQ,
    },
    {
        .start    =    TI816X_IRQ_MACMISC1,
        .end    =    TI816X_IRQ_MACMISC1,
        .flags    =    IORESOURCE_IRQ,
    },
};

static struct resource ti816x_emac2_resources[] = {
    {
        .start    =    TI816X_EMAC1_BASE,
        .end    =    TI816X_EMAC1_BASE + 0x3FFF,
        .flags    =    IORESOURCE_MEM,
    },
    {
        .start    =    TI816X_IRQ_MACRXTHR0,
        .end    =    TI816X_IRQ_MACRXTHR0,
        .flags    =    IORESOURCE_IRQ,
    },
    {
        .start    =    TI816X_IRQ_MACRXINT0,
        .end    =    TI816X_IRQ_MACRXINT0,
        .flags    =    IORESOURCE_IRQ,
    },
    {
        .start    =    TI816X_IRQ_MACTXINT0,
        .end    =    TI816X_IRQ_MACTXINT0,
        .flags    =    IORESOURCE_IRQ,
    },
    {
        .start    =    TI816X_IRQ_MACMISC0,
        .end    =    TI816X_IRQ_MACMISC0,
        .flags    =    IORESOURCE_IRQ,
    },
};

static struct platform_device ti816x_emac1_device = {
    .name    =    "eth_offload",
    .id    =    0,
    .num_resources    =    ARRAY_SIZE(ti816x_emac1_resources),
    .resource    =    ti816x_emac1_resources,
};

static struct platform_device ti816x_emac2_device = {
    .name    =    "davinci_emac",
    .id    =    1,
    .num_resources    =    ARRAY_SIZE(ti816x_emac2_resources),
    .resource    =    ti816x_emac2_resources,
};

In ti816x_ethernet_init function,

ti816x_emac1_pdata.hw_ram_addr = TI816X_EMAC2_HW_RAM_ADDR;
ti816x_emac1_device.dev.platform_data = &ti816x_emac1_pdata;
platform_device_register(&ti816x_emac1_device);

...

ti816x_emac2_pdata.hw_ram_addr = TI816X_EMAC1_HW_RAM_ADDR;
ti816x_emac2_device.dev.platform_data = &ti816x_emac2_pdata;
platform_device_register(&ti816x_emac2_device);

...

init console log:

...

davinci_mdio davinci_mdio.0: davinci mdio revision 1.6
davinci_mdio davinci_mdio.0: detected phy mask ffffff76
davinci_mdio.0: probed
davinci_mdio davinci_mdio.0: phy[0]: device 0:00, driver unknown
davinci_mdio davinci_mdio.0: phy[3]: device 0:03, driver unknown
davinci_mdio davinci_mdio.0: phy[7]: device 0:07, driver unknown

...

Thanks in advance.