Hi Suman, On Tuesday 09 September 2014 17:31:44 Suman Anna wrote: > > On Tuesday 09 September 2014 16:33:11 Suman Anna wrote: > >> On 09/09/2014 10:45 AM, Laurent Pinchart wrote: > >>> The OMAP IOMMU driver supports both the OMAP1 and OMAP2+ IOMMU variants > >>> by splitting the driver into a core module and a thin arch-specific > >>> operations module. > >>> > >>> (In practice only the OMAP2+ module omap-iommu2 is implemented, but > >>> let's not denigrate the effort.) > >> > >> Thank you for the patch. I had something similar in my list of cleanup > >> TODO items on the OMAP IOMMU driver, but I was intending to cut down > >> more and consolidate the omap-iommu.c and omap-iommu2.c files into a > >> single one. > >> > >> This had been the case from the introduction of the driver going back to > >> v2.6.30, and OMAP1 was never added and I doubt it would be added anytime > >> in the foreseeable future. > >> > >>> The arch-specific operations module registers itself with the OMAP IOMMU > >>> core module at initialization time. This initializes a module global > >>> arch-specific operations pointer, used at runtime by the IOMMU > >>> instances. > >>> > >>> This scheme causes several issues. In addition to making it impossible > >>> to support different OMAP IOMMU types in a single system (which in all > >>> fairness is quite unlikely to happen), > >> > >> Yep, except for a few enhancements (like reporting Fault PC address on > >> OMAP4 DSPs, and dropping both endianness support), the core IOMMU > >> functionality hasn't changed much between OMAP2 and the latest OMAP4+ > >> SoCs. So, my plan was to completely get rid of the iommu_functions (it > >> also eliminates the need for exporting most of the OMAP IOMMU API). So > >> while I am ok with the current patch, I prefer consolidation than > >> keeping the scalability alive, it can always be added if a need for that > >> arises. What do you think? > > > > I agree with your approach, but in the meantime we have a problem to > > solve. > > How about applying this patch now (it goes in the right direction anyway), > > and then removing the iommu functions when you will have time ? > > Can you give the subsys_initcall solution a try to see if that resolves > the problem at hand? That would be a much smaller change, if that > doesn't work we can go with this patch. It seems to work. > I will work on my cleanup list for 3.19. Does that schedule still hold ? If so I'll submit a simple subsys_initcall() patch for v3.18. > >> it also causes initialization > >> > >>> ordering issues by requiring the arch-specific operations module to be > >>> loaded before any IOMMU user. This results in a probe breakage with the > >>> OMAP3 ISP driver when not compiled as a module. > >> > >> This can be fixed if we make the current omap-iommu2.c as a > >> subsys_initcall as well, right? > >> > >> regards > >> Suman > >> > >>> Fix the problem by inverting the dependency. Instead of having the > >>> omap-iommu2 module register itself to iommu-omap, make the iommu-omap > >>> retrieve the omap-iommu2 operations structure directly when probing the > >>> IOMMU device. This ensures that a probed IOMMU will always have valid > >>> arch-specific operations. > >>> > >>> As the arch-specific operations pointer is now initialized at probe > >>> time, this change requires turning it from a global variable into a > >>> per-device variable. > >>> > >>> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > >>> --- > >>> > >>> drivers/iommu/omap-iommu-debug.c | 6 ++- > >>> drivers/iommu/omap-iommu.c | 94 +++++++++++++-------------------- > >>> drivers/iommu/omap-iommu.h | 10 ++++- > >>> drivers/iommu/omap-iommu2.c | 18 +------- > >>> 4 files changed, 45 insertions(+), 83 deletions(-) -- Regards, Laurent Pinchart -- 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
