Hi Linux Experts,
I received a software question on the PMU forum. I am pasting the question and the original thread link below. I cannot move the thread as this was filed as a continuation of the previous hardware question. I hope someone will be able to help.
http://e2e.ti.com/support/power_management/pmu/f/43/p/37488/291332.aspx#291332
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I'm still looking for a resolution to this same issue.
There is no code in the PSP drivers to write to OTG_CTRL however the registers are clearly defined in usb/otg/twl4030-usb.c. I find that if in that driver I attempt to clear DRVVBUS bit via 'twl4030_usb_write(twl, TWL4030_OTG_CTRL_CLR, TWL4030_OTG_CTRL_DRVVBUS);' PMIC VBUS does go to 0V but some other driver/code immediately sets the big and VBUS goes back up to 5V again.
I also find that Cliffs recommendation to not set MUSB_DEVCTL_SESSION in drivers/usb/musb_core.c does in fact somehow (?) clear the OTG_CTRL[5]:DRVVBUS bit and as Cliff mentions also keeps your bus from enumerating thus it has some other effects. Its not clear to me why this was suggested - I believe the MUSBHDRC specs are not publicly available thus I can't investigate that driver much.
I find it very frustrating that the responses here from TI seem very knowledgeable about the hardware end but never have any clue as to the software end that the PSP group is working on.
Any suggestions?
Thanks,
Tim
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Regards,
Gandhar.