On 21.12.2022 22:32, Sam Protsenko wrote: > Hi Marek, > > On Mon, 24 Oct 2022 at 09:43, Sam Protsenko <semen.protsenko@xxxxxxxxxx> wrote: >> Hi Marek, >> >> On Fri, 12 Aug 2022 at 14:25, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: >>> Hi Sam, >> [snip] >> >>>> Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx> >>> I'm not very happy with converting the sysmmu_fault_info arrays into the >>> decoding functions. If I got the code right, adding v7 is still possible >>> with the current approach. The main advantage of the array-based >>> approach is readability and keeping all the information together in a >>> single place. >>> >>> I agree for the items listed above as 'minor functional changes', >>> though. Those sysmmu_fault_info arrays might be a part of sysmmu hw >>> variant to avoid decoding hw version for each fault. >>> >>> I'm not sure that the linear scan is so problematic with regards to the >>> performance. You really don't want your drivers to trigger IOMMU fault >>> so often during normal operation. It is just a way to get some debugging >>> information or handle some exception. >>> >>> You mentioned that the transaction type is read from the separate >>> register in case of v7, but your code (here and in second patch) still >>> relies on the reported interrupt bits. >>> >>> Could you try to rework all your changes in a such way, that the >>> sysmmu_fault_info arrays are still used? V7 is really very similar to >>> the v5 already supported by the current driver. >>> >> That's actually how I implemented this patch on my first attempt. >> Really didn't like it, because a half of existing sysmmu_fault_info >> structure doesn't make sense for v7, and some functionality of v7 has >> to be implemented separately from that structure. I'd argue that >> previous abstraction is just broken, and doesn't work for all SysMMU >> versions anymore. It's easy to see how much difference between v5 and >> v7, just by looking at corresponding get_fault_info() functions I >> implemented. For example, the transaction type is probed from >> different registers using different version, etc. There is also the >> need to handle new VM/non-VM registers on v7. Also there is some extra >> functionality that will be added later, like multiple translation >> domains support, which is also quite different from how things done >> for v5. >> >> I'd show more specifics to demonstrate my statements above, but alas I >> already deleted my initial implementation (which was exactly what you >> suggest). This callback-style HAL seems to be a perfect choice, and I >> spent several days just experimenting with different approaches and >> seeing all pros and cons. And from my point of view, this way is the >> best for providing actual solid abstraction, which doesn't require >> adding any workarounds on top of that. I understand that my patch >> changes the very conception of how IRQ is handled in this driver, but >> I'm still convinced it's a proper way to do that for all v1/v5/v7, >> especially w.r.t. further v7 additions, to keep the abstraction solid. >> Not that I'm lazy and don't want to rework things :) But in this >> particular case I'd go with unchanged patches. >> >> Do you think it's reasonable to take this series as is? I can try and >> collect more particular code snippets to demonstrate my point, if you >> like. >> >> Thanks! > So, what do you think about this? Okay, go ahead with your approach. If I find a better way, I will rework it then. I would just like to have the code for fault handling for hw v1, v5 and v7 similar as much as possible. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
