On Thu, Oct 18, 2012 at 21:44:56, Hunter, Jon wrote: > Hi Gururaja, > > On 10/18/2012 12:31 AM, Hebbar, Gururaja wrote: > > Jon, > > > > On Thu, Oct 18, 2012 at 02:42:01, Hunter, Jon wrote: > > [snip] > > >>> My doubt/questions are > >>> 1. Why should debounce registers be updated only when it's accessed previously? > >> > >> If debounce is not being used by any of the gpios, then there is no need > >> to restore them as there are no bits set. So this makes sense and saves > >> a couple register writes. > > > > What I want to know is that other than saving register writes, is there any > > other important stuff that specifies this requirement. > > From a HW perspective, none that I can see. > > From a SW perspective, yes, as I mentioned if you restore these > registers without first initialising the context variables where these > registers are stored, then you may be restoring unknown values to the > registers and that is bad. > > >>> 2. What is the relation between updating debounce registers and crash seen on > >>> others registers? > >> > >> This I am not sure about. I gave this a quick try on my omap3430 beagle > >> board, but I did not see any side-effects from doing this. However, if > >> you are always restoring the debounce context regardless of whether > >> debounce is being used, then you could be writing bad values to the > >> debounce registers as the context variables bank->context.debouce and > >> bank->context.debouce_en may not initialised. So that is bad. However, > >> that said I am still not sure how this could cause a crash. > >> > >> Can you share more details on ... > > > > Sorry for missing below details in first post. > > > >> 1. The OMAP platform you are using? > > > > I was trying this on TI AM335x platform (repo below). On AM335x EVM board > > > > http://arago-project.org/git/projects/?p=linux-am33x.git;a=shortlog; > > h=refs/heads/v3.2-staging > > > >> 2. What linux distro/environment you are using? > > > > Arago AM335x PSP release (linux 3.2 + am335x patch-set) > > > >> 3. If there are any specific steps to reproduce this 100% of the time? > > > > On top of this tree, try suspend/resume using "echo mem > /syspower/state" > > I have a beagle-bone but unfortunately, suspend does not appear to be > supported in the mainline kernel yet so I am unable to test this on the > am335x on the mainline. You can try the suspend/resume on BB from Arago tree which I mentioned above > > Have you compared the gpio driver from your v3.2 branch with the current > mainline to see how different this code is? Ideally, it would be good to > test on the mainline kernel for another data point to see if this is > local to your branch. The mainline kernel omap GPIO driver has changed a lot from current arago tree (which is at v3.2). Upon comparing is when I found out about the register access check done before restoring. > > Cheers > Jon > > > Regards, Gururaja -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
