* Paul Walmsley <p...@pwsan.com> [110702 21:09]: > Hi Tony > > On Thu, 30 Jun 2011, Tony Lindgren wrote: > > > NAK for this patch. We don't want any of this in init_early. > > > > The problem is with hwmod core code that wrongly assumes it > > can just reset all devices. > > I don't think the hwmod core code has any way of knowing which devices > shouldn't be reset unless the board file specifically tells it. Even if > the reset happens right before the hwmod enable (as called by the device > driver), the 4460 boards would still crash when the GPIO driver starts. > > What you suggested below should allow those omap_hwmod_no_setup_reset() > calls to live in init_machine, rather than init_early. Hopefully that is > acceptable? So I did a test implementation of your idea, and learned some > good news and bad news.
Yes later on that should be fine, but preferrably not until late_initcall so we have decent debug output even without DEBUG_LL being enabled. > The good news is that it seems to work for the PM runtime-converted > drivers. omap_hwmod_no_setup_reset() calls can go into init_machine code. > We should also be able to get rid of the postsetup code in > mach-omap2/io.c. > > The bad news is that the unused IP block reset code will reset IP blocks > used by drivers that haven't been converted to use runtime PM. The hwmod > core code doesn't know that those IP blocks are in use, since > omap_hwmod_enable() is never called for them. The unused IP block reset > code will then reset those blocks after the drivers have already probed, > and the drivers are not expecting this :-) I guess we should keep it disabled for now :) > GPTIMER and HSMMC drivers are the obvious problems in terms of getting a > successful boot, but DSS is another one that may cause some problems here. > There are HSMMC and DSS driver PM runtime conversion patches posted, > hopefully they will go into mainline soon, but there are probably some > other important drivers yet to be converted or yet to be pushed. > > Here are some options that come to mind: > > 1. Wait until the driver runtime PM conversion is finished before doing > anything. In the meantime, boards with IP blocks that can't be reset > - N810, TI 4460 boards - will have problems. > > 2. Merge the lazy/unused hwmod reset code, but prevent IP blocks > controlled by non-runtime PM drivers from being reset. We'd have to > maintain a list of these somewhere, perhaps in some common code called > by board file init_machine code. Then we'd need to redact that list as > new driver runtime PM conversions complete. > > 3. Merge the lazy/unused hwmod reset code, but disable the unused hwmod > reset code until the driver runtime PM conversion is finished. This > could cause problems with driverless devices that are left configured > by bootloaders or ROM code, and that problem would reoccur for each new > OMAP chip. > > Do you have a preference as to which approach to take? I think #3 above is the safest option. How about make it only happen with hwmod_reset=1 cmdline with 0 being the default value? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
