On Fri, Jun 20, 2014 at 11:17 PM, Doug Anderson <dianders@xxxxxxxxxxxx> wrote: > Hi, > > On Fri, Jun 20, 2014 at 4:19 AM, amit daniel kachhap > <amit.daniel@xxxxxxxxxxx> wrote: >> On Fri, Jun 20, 2014 at 1:45 PM, Will Deacon <will.deacon@xxxxxxx> wrote: >>> On Thu, Jun 19, 2014 at 05:40:49PM +0100, Tomasz Figa wrote: >>>> On 19.06.2014 18:31, Doug Anderson wrote: >>>> >>> My personal vote would be to submit a patch to change "cycles_t" to >>>> >>> always be 32-bits. Given that 32-bits was fine for udelay() for ARM >>>> >>> that seems sane and simple. If someone later comes up with a super >>>> >>> compelling reason why we need 64-bit timers for udelay (really??) then >>>> >>> they can later add all the complexity needed. >>>> >> >>>> >> Yes, this could work. I'm not sure what else cycles_t is used for, though. >>>> > >>>> > True, it is a bit questionable to change this since it's a type that's >>>> > not obviously just for udelay(). Perhaps a better option would be to >>>> > make a new typedef for the result of read_current_timer(). ...or just >>>> > change it to return a u32? >>>> > >>>> >>>> Sounds good to me, but let's hear other opinions. I'm adding Will and >>>> Jonathan as they wrote the ARM delay timer code. >>> >>> I think cycles_t is only used for small interval calculations at the moment, >>> but I remember Ted mentioning something about using it (or something >>> similar) as a source of early entropy, in which case the more bits the >>> better. >>> >> Will, >> Thanks for the clarification that cycles_t is used for short >> intervals. So it is safe to return lower 32 bit >> counter for read_current_timer. > > As I looked at it more, I realized that we have two types in Linux. > There's cycle_t and cycles_t. Whoa, confusing! > > I'd perhaps advocate a wholesale rename of cycles_t to avoid the > confusion. I don't have a good name for it, though. cycle32_t? Or > we could just use u32 for the function... :-/ or cycles_t can be renamed as short_cycle_t > > >> Tomasz, Doug, >> As of now let me send a minimal implementation of this read delay >> timer to fix the broken udelay for exynos platforms so that it goes to >> upstream in rc releases. I will also prepare a fix for all >> raw_readl/writel in mct to relaxed version to make it consistent. > > I'm reworking my 32-bit conversion patches right now and it's getting > messy to intermingle this with yours. I'm going to pick up your patch > and include it in my series. I hope that's OK. its fine and thanks for posting the series. > > My plan is: > > 1. For 3.16 I think it's important to fix the udelay() problems and > trying to rework cycle_t there doesn't seem like it makes sense. I'll > just use Amit's original code that uses exynos_frc_read(). It might > not be quite as optimal but it's good as a safe bugfix. > > 2. I'll post the cleanup patch moving away from the __raw_readl / __raw_writel > > 3. I'll post a patch moving to 32-bit, including moving Amit's code to > 32-bit but with a compile time warning for now. I'll add a KConfig > depends to keep it from compiling on ARM64. We can improve this once > we change the delay timer to always request 32-bits. > > -Doug > -- > To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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