Hi Laurent, > 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. I will work on my cleanup list for 3.19. regards Suman > >> 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(-) > -- 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
