OMAP-L137: Downstream signal quality question

Hi Ryo,

"load once" means the test packet to be written to the FIFO once and it will be transmitted repeatedly forever until reset. In typical usb transfers the FIFO becomes empty once the packet is transmitted.

Your sequence 1-4 seems to be correct. Please ensure you use the index address of EP0 and made EP0 index active when accessing EP0 registers.

Here is how Linux driver does it.

400                         case 4:
401                                 pr_debug("TEST_PACKET\n");
402                                 temp = MUSB_TEST_PACKET;
403                                 musb_load_testpacket(musb);
404                                 break;
...
420                         musb_writeb(musb->mregs, MUSB_TESTMODE, temp);

musb_load_testpacket() is defined as:

 439 void musb_load_testpacket(struct musb *musb)                                    
 440 {                                                                               
 441         void __iomem    *regs = musb->endpoints[0].regs;                        
 442                                                                                 
 443         musb_ep_select(musb->mregs, 0);                                         
 444         musb_write_fifo(musb->control_ep,                                       
 445                         sizeof(musb_test_packet), musb_test_packet);            
 446         musb_writew(regs, MUSB_CSR0, MUSB_CSR0_TXPKTRDY);                       
 447 }