Hi, Bin Liu <b-liu@xxxxxx> writes: > On 11/13/2015 06:57 PM, Greg KH wrote: >> On Fri, Nov 13, 2015 at 03:45:24PM -0600, Bin Liu wrote: >>> Change the permission of usb_dma parameter so it can be used for runtime >>> debug without reboot. >> >> Why would you want to do that? This is only used at init time, so if >> you change it while the driver is running, I don't think you will >> actually affect anything. > > During debug, I want to run with CPPI enabled or disabled without reboot > the board to load different kernel image. > > With this patch, I can archive this by > > - unbind musb_hdrc > - change usb_dma param > - bind musb_hdrc > >> >> Have you tested this out? > > Yes, I did and it works for me. this is correct, we check use_dma every time before starting a DMA transfer. But claiming that you need to reboot is kinda dodgy. You could very well rmmod/modprobe with the different parameter ;-) In any case, this is useful and causes no regressions, I'll take it anyways. -- balbi
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