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USB suspend resume issue on Vybrid

Question asked by Sanchayan Maity on Sep 13, 2015
Latest reply on Mar 22, 2016 by markwilliams



I am working on Freescale Vybrid with a Chipidea based USB controller and a Sigmatel Phy or something if my memory serves me right. We are currently in the process of implementing suspend resume and fixing related issues. After resume the USB PHY does not come up and the USB subsytem prints


[129.570097] usb 1-1: USB disconnect, device number 2


which comes from the core code in hub.c.


I am using the 4.1.5 kernel with some of our own patches especially with regards to suspend resume being present only in our own tree which we plan to eventually push out to mainline.


From what I can see, the USB USBPHYx_PWDn register which has bits related to power down, all stay in their default "1" state which denotes power down, after resume. Now this is in spite of the fact that the code seems [2] to write 0 to the register on resume. However, doing a quick check with devmem2 shows the register to have the default values of "1" denoting power down. So write seems to have no effect at all.


Instead of the code at lines 392[1] and 394[2] if I do


return mxs_phy_hw_init(mxs_phy);


on resume, the USBPHYx_PWDn seems to have the correct value of all bits as zero. However of course, the USB PHY does not come up. The stmp block reset in mxs_phy_hw_init seems to make the write work.


There is an errata for Vybrid at [3] in VYBRID_2N02G going as e4535: USB: USB suspend and resume flow clarifications. Not sure if I understand the explanation, however the following workaround which the errata mentions:


To place the USB PHY in low power suspend mode, the following sequence should be performed in an atomic operation. (interrupts should be disabled during these three steps)


1. Set the PORTSC1.PHCD bit

2. Set all bits in USBPHY_PWD register



These sequence of steps seem to be correctly followed in the suspend code [4] of Chipidea IP AFAICT.


I am not that well versed with USB subsystem code having only worked on it once before for fixing non working USB client on Vybrid [5]. Have tried messing with different register bits in the USB PHY, USBPHY_CTRL and USB miscellaneous register like UTMI_SUSPENDM, HOST_FORCE_LS_SE0 and HOST_RESUME_DEBUG but with no results. Have already made sure that all the ANADIG and CCM registers are at their correct values after resume.


From what I can see this seems to be USB PHY issue.


MXS_PHY_ABNORMAL_IN_SUSPEND and MXS_PHY_SENDING_SOF_TOO_FAST, these two flags are not implemented in mainline. However implementing them with old patches from mainline and the way it is done in Freescale's 3.14 kernel release does not help either.


Is there an errata with the USB suspend resume issue of Chipidea IP core and Sigmatel PHY on Vybrid? Can anyone from Freescale or one of the hardware IC engineers know of steps to bring up the USB PHY on resume?


Thanks & Regards,