AM335X USB DMA question

Y tck

Hi All:

We are using AM335X in our project and have looked at the starterware examples. We use one of the USB controller of the AM335X as a USB bulk device. The cppi DMA mode is to be used, We are using the Cppi41DmaModeSet function in the file of cppi41dma.c of staterware to set the working mode of the CPPI DMA controller. However, it seems doesn't work , we can't change the DMA working mode to be RNDIS or GRNDIS ,but only theTRANSPARENT mode( default mode ) can be used.

We checked the Cppi41DmaModeSet function in the file of cppi41dma.c of staterware carefully, the Registers and Base address used in this fuction seems diffetent with the the Registers of the USB module listed and descripted in the datasheet of AM335X. The differences bewteen the esample code and the datasheet are as follow:

The usbInstance->otgBaseAddress is initialized to the base address of USBSS In the Cppi41DmaInit function, in the Cppi41DmaModeSet function. usbInstance->otgBaseAddress is used as the base address of the USB0CTRL Register and USB0MODE Register , but we can't find USB0CTRL Register and USB0MODE Register in the Registers list of USBSS , however, we find these registers in the Registers list of USB0_CTRL and USB1_CTRL . In additon, the USB0MODE Register (USB_0_MODE) appeared in the Cppi41DmaModeSet function is not used for DMA working mode setting but for IDDIG, PHY_TEST and LOOPBACK setting accordding to the datasheet of the USB0_CTRL in AM335X. For DMA working mode setting, there seems exist two registers as USB0TXMODE register and USB0 RXMODE register in the registers list of USB0_CTRL.

Now , we are confused by the example code in starerware and the datasheet of AM335x, Although we have do a lot of code debugging work , it still doesn't work.

Can anyone from TI help us to solve this problem?

Best Regards

Y tck

over 11 years ago

0 Y tck over 11 years ago

Intellectual 835 points

Can anyone help us?

0 Qmax over 11 years ago

Expert 2280 points

IMHO Cppi41DmaModeSet code is completely wrong!

Naming register as in TRM, the ones to be configured are: USB0CTRL USB0TXMODE USB0RXMODE and USB0GENRNDISEPx.

All these registers are part of USB0 registers block (aka USB0_CTRL), so the base address to be used would be 0x47401000 and not otgBaseAddress (0x47400000).

Global RNDIS must be set/reset in USB0CTRL register, as is.

TX/RX EPs configuration must be done setting USB0TXMODE and USB0RXMODE registers: using USB0MODE reg here seems a nonsense...

Configuration of USB0GENRNDISEPx seems hard-coded just for first EP (USB_0_GEN_RNDIS_SIZE_EP1), all other EPs are ignored...

I wonder how it can work... ...if works.

I would suggest to rewrite it by yourself. And try to ask help on Starterware forum, too.

Regards,

Max

0 Y tck over 11 years ago in reply to Qmax

Intellectual 835 points

    Thank you for answering our question. In fact , before asking this question in TI E2E Community, We have already tried to rewrite the Cppi41DmaModeSet function, using registers of USB1CTRL USB1TXMODE USB1RXMODE and USB1GENRNDISEPx . Currently in our project , we just use RX and TX endpoint 1 of USB1 module for data receiving and transmitting. However , The rewritten Cppi41DmaModeSet function still dosen't work . The Cppi41DmaModeSet code is as follow:

void Cppi41DmaModeSet(unsigned short usbDevInst, endpointInfo *epInfo)
{

    unsigned int rxModeReg;
    /* Enable RNDIS from Global Level */
    if (epInfo->dmaMode == CPDMA_MODE_SET_RNDIS)
    {
        HWREG(0x47401800 + 0x14)|= CPDMA_MODE_ENABLE_GLOBAL_RNDIS;

    }
    /* Disable RNDIS from Global Level     */
    else
    {
        HWREG(0x47401800 + 0x14)&= ~CPDMA_MODE_ENABLE_GLOBAL_RNDIS;
    }

    /*Set the mode for RX and TX channel */
    if(epInfo->direction == CPDMA_DIR_TX)
    {
        HWREG(0x47401800 + 0x70)|= 0x00000003; //EP1 GRNDIS TX MODE
    }
    else
    {
        HWREG(0x47401800 + 0x74)|=0x00000003;   //EP1 GRNDIS RX MODE

    }
    /* For GRNDIS mode, set the maximum packet length */
    if (epInfo->dmaMode == CPDMA_MODE_SET_GRNDIS)
    {
        if(usbDevInst == 0)
        {
            HWREG(0x47401000 + 0x80) = GRNDIS_MAX_PACKET_LENGTH;
        }
        else if(usbDevInst == 1)
        {
            HWREG(0x47401800 + 0x80) = GRNDIS_MAX_PACKET_LENGTH;

        }
    }
}

    In Cppi41DmaModeSet function, 0x47401800 is the base address of USB1 module, 0x14 0x70 0x74 0x80 are the offset address of USB1CTRL USB1TXMODE USB1RXMODE and USB1GENRNDISEPx , other MACRO definitions used in the function are not changed.

    Unfortunately , the rewritten function of Cppi41DmaModeSet still doesn't work , it seems any change to any register used in this function doesn't make any response when running the program. Now We suspect that there may be something error in the register list of USB0/1 module of AM335X datasheet. Could you tell me whether my doubt is right or wrong? If there is a new version of AM335X , Could you give me a copy? Thanks!

   Best regards,

Y tck

0 Qmax over 11 years ago in reply to Y tck

Expert 2280 points

Do you mean a new version of AM335x TRM doc? A do not think registers are wrong.

I cannot help too much, I played with Starterware just a few hours some months ago, but PSP Linux kernel uses same registers definition as TRM, and seems working. BTW kernel uses just TRANSPARENT and GRNDIS modes, and last one only if pkt size is multiple of 64 (except some ad-hoc cases in peripheral mode for rx channels).

Of course function logic is wrong, 'cause enabling/disabling RNDIS at global level cannot be handled by EP-specific configuration, but if I do not think this is the point.

In Starterware, comparing 2.0.0.5 with 2.0.0.7 versions, I've noticed that in several examples (dev_msc, host_msc), they moved TX channels configuration from GRNDIS to TRANSPARENT. Maybe if someone at TI can say way, this could help you. Are you able to run Starterware examples as they are?

Also note this detail here: In the current implantation, GRNDIS mode will not work if the packet size is larger than 512 bytes.

Regards

0 Joe G. over 11 years ago in reply to Qmax

TI__Mastermind 25746 points

You guys are way beyond me in USB DMA detail, but have you seen the Silicon Advisory 1.0.13 on p. 16 of http://www.ti.com/litv/pdf/sprz360b ?

Hence we have been running (in Linux) without USB DMA and the delta is not too bad (at least documented in this version of the PSP: http://processors.wiki.ti.com/index.php/AM335x-PSP_04.06.00.06_Features_and_Performance_Guide#USB_MSC_.28MUSB.29_Host_mode_VFAT_File_System_Performance )

0 Qmax over 11 years ago in reply to Joe G.

Expert 2280 points

Joe, thanks for outlining the silicon issue. I already know about it (I'm working on USB and AM335x since several months), but I do not think it's the case of Ytck: in my understanding he is using just a single endpoint.

Yeah, not using DMA will be fine if performances are not so critical for you product. But as you can see host MSC PIO read performances are less than half DMA ones. In general performances depend on a lot of parameters: host/peripheral role, implemented USB classes and functions, device at the other side of cable, etc... DMA can help. And it also offloads the cpu. BTW if you look at PSP 4.6.0.8 performances seem even worst than 4.6.0.6 (only DMA avail).

For my project USB performances are really critical. And it was already in an advanced state when Silicon Advisory came out. Now I'm digging around, but...

0 Y tck over 11 years ago in reply to Qmax

Intellectual 835 points

Max,thank you for your answer, but the problem still exists. I have downloaded the Starterware 2.0.0.7 version, and I find that the Cppi41DmaModeSet function in cppi41dma.c has no change, it's still completely wrong. Just like you, I also find that in evm335x examples, dev_msc, host_msc, the TX channels DMA configuration have been changed from GRNDIS to TRANSPARENT , Why they do that? Maybe the GRNDIS mode of CPPI DMA could never work actually? Maybe some example codes of starterware haven't been tested strictly? How could I contact someone work in TI that can solve my question?

In addtion, I have set the maxium packet size of the Rx and Tx endpoint 1 as 512 bytes, I think that could meet the requirement of the"GRNDIS mode will not work if the packet size is larger than 512 bytes", or maybe the “packet size” in this sentence has some other meaning ? Thack you for help!

Best regards

Y tck

0 Y tck over 11 years ago in reply to Y tck

Intellectual 835 points

Can anybody help me?

0 Keegan@TI over 11 years ago in reply to Y tck

TI__Expert 5740 points

Bump. Any new insight into this issue?

0 zumeng chen over 11 years ago in reply to Keegan@TI

Intellectual 650 points

Joe, would you please help me to get this doc http://www.ti.com/litv/pdf/sprz360bas you mentioned here, thanks in advance.

Yes, the performance of DMA mode is just equals to PIO mode, so I guess CPPI41 DMA work pretty none :-)

0 Vineeth Balan over 11 years ago in reply to Keegan@TI

TI__Intellectual 1640 points

Hi Everyone ,

My apologies for taking so long.

There are some documentation gaps in the AM335x documentation. At places the register description is wrong and the MUSB controller section is incomplete.

Please refer the following post for the link to download the DM814x TRM . This controller has the same register offsets as AM335x.

http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/204049.aspx

With regard to your query on DMA mode being changed in the latest StarterWare release , this was done to circumvent an silicon issue which popped up in GRNDIS mode. As an example, when the controller was being configured as an MSC device ( this seems to be your case) Tx can be performed using GRNDIS mode but Rx needs to be done using the TRANSPARENT DMA mode.

0 zumeng chen over 11 years ago in reply to Vineeth Balan

Intellectual 650 points

Thanks Vineeth, I have gotten the document, thanks!

0 Joe G. over 11 years ago in reply to zumeng chen

TI__Mastermind 25746 points

Lit # changed to http://www.ti.com/litv/pdf/sprz360c

Probably bad idea for me to post direct links anyway. You can always go to the product page and download the latest:

http://www.ti.com/product/am3358

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AM335X USB DMA question