Linux USB - Configuring the USB host (musb-hdrc?) to only allow

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Last Post 02 Nov 2018 04:19 PM by Charlie Hamilton

Linux USB - Configuring the USB host (musb-hdrc?) to only allow connections in full-speed mode (disable high-speed)?

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steven.eckhoff

Basic Member
Posts:192

17 Oct 2013 09:07 AM
Hi, Do you know how to configure the USB host (musb-hdrc?) to only allow connections in full-speed mode (disable high-speed)? We are having issues with some USB devices and would like to force the bus to run slower. Thanks for your help Matt

steven.eckhoff

Basic Member
Posts:192

18 Oct 2013 10:03 AM
You can try using the following: echo "force full-speed" > /debug/musb/testmode If you do not see the debug filesystem, then you can add it by doing the following in the kernel config Menuconfig->kernel hacking --> [ ] Enable unused/obsolete exported symbols [] Debug Filesystem [ ] Run 'make headers_check' when building vmlinux [] Kernel debugging

Matt Sacker

New Member
Posts:4

18 Oct 2013 10:51 AM
Hi Steven, I have tried waht you suggested but the USB device still connects at high speed. I have managed to force full speed by recompiling the kernel, following the instructions here: http://www.spinics.net/li...ux-usb/msg93739.html diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c index daec6e0..8bbe1a9 100644 --- a/drivers/usb/musb/musb_core.c +++ b/drivers/usb/musb/musb_core.c @@ -928,7 +928,7 @@ void musb_start(struct musb musb) / put into basic highspeed mode and start session / musb_writeb(regs, MUSB_POWER, MUSB_POWER_ISOUPDATE - \| MUSB_POWER_HSENAB + / \| MUSB_POWER_HSENAB / / ENSUSPEND wedges tusb / / \| MUSB_POWER_ENSUSPEND */ ); However, I would prefer a solution that does not require a kernel re-compile. Do you have any other suggestions? Thanks for your help Matt

steven.eckhoff

Basic Member
Posts:192

18 Oct 2013 05:56 PM
Matt, That method should work. If it is not working I will need to look into what is going on. I will also look for an alternative.

Matt Sacker

New Member
Posts:4

21 Oct 2013 11:38 AM
Hi Steven, I have tried your method a couple of times, but it seems the device still appears as a high speed device. Is there anyway to confirm the command has been received? Thanks for your help Matt

steven.eckhoff

Basic Member
Posts:192

21 Oct 2013 11:56 AM
Matt, I will need to spend some time digging into this issue.

Charlie Hamilton

New Member
Posts:2

02 Nov 2018 04:17 PM
Note that Steven's method only applies to running the controller in host mode. Note also that it will not work, per the OMAP TRM, you can't just set the full-speed bit. I added code to check for two more strings to set the controller into full speed test mode and kick off a test packet sequence into the debugfs in the function must_test_mode_write: if (!strncmp(buf, "host full", 9)) { // Per TEST_MODE reg documentation, host and fullspeed mode are // enabled when the session mode bit is set to 1. Clear it, // Configure the test mode register with host and fs set, then // write a 1 to the session bit. devctl = musb_readb(musb->mregs, MUSB_DEVCTL); devctl &= ~MUSB_DEVCTL_SESSION; musb_writeb(musb->mregs, MUSB_DEVCTL, devctl); test = MUSB_TEST_FORCE_HOST \| MUSB_TEST_FORCE_FS; musb_writeb(musb->mregs, MUSB_TESTMODE, test); musb_writeb(musb->mregs, MUSB_DEVCTL, devctl \| MUSB_DEVCTL_SESSION); test = 0xFF; } if (!strncmp(buf, "test packet full", 16)) { test = MUSB_TEST_PACKET \| MUSB_TEST_FORCE_HOST \| MUSB_TEST_FORCE_FS; musb_load_testpacket(musb); } Note that test mode does not affect normal operation, and you should use Matt's brute force method of rebuilding the kernel.

Charlie Hamilton

New Member
Posts:2

02 Nov 2018 04:19 PM
Note that I meant "running the controller in test mode" in the first sentence, not "host mode"