Hi, On Thu, Sep 1, 2016 at 7:35 PM, Ziyuan Xu <xzy.xu@xxxxxxxxxxxxxx> wrote: > > > On 2016年09月02日 05:29, Doug Anderson wrote: >> >> Hi, >> >> On Wed, Aug 31, 2016 at 11:56 PM, Ziyuan Xu <xzy.xu@xxxxxxxxxxxxxx> wrote: >>> >>> Hi >>> >>> >>> On 2016年09月01日 12:20, Doug Anderson wrote: >>>> >>>> Hi, >>>> >>>> On Wed, Aug 31, 2016 at 7:29 PM, Ziyuan Xu <xzy.xu@xxxxxxxxxxxxxx> >>>> wrote: >>>>>> >>>>>> This is fine to pick up _only_ if you don't care about suspend/resume. >>>>>> If you care about suspend/resume then someone needs to first write a >>>>>> patch that will re-init all "corecfg" values after power is turned on. >>>>> >>>>> >>>>> Do you mean corecfg_clockmultiplier and corecfg_baseclkfreq, if yes, we >>>>> don't need to strore/re-init it after resume. >>>>> corecfg_clockmultiplier is only used to fetch host->clk_mul, and >>>>> host->clk_mul has been a fixed value at run-time, unless driver unbind. >>>>> The same as corecfg_clockmultiplier, corecfg_baseclkfreq is used to >>>>> check >>>>> the xin_clk at probe time, we don't reference it at run-time. >>>>> BTW, I have tested suspend/resume on rk3399 prior to this sumbit, eMMC >>>>> works >>>>> fine. >>>> >>>> I guess I don't actually know how the corecfg_clockmultiplier and >>>> corecfg_baseclkfreq fields are actually used, but I presume that they >>>> actually do something useful and aren't used to just communicate back >>>> to software? >>> >>> >>> Take corecfg_clockmultiplier as example. >>> 1. sdhci driver fetch host->clk_mul from corecfg_clockmultiplier >>> 2. mmc->f_min and mmc->f_max are calculated via host->clk_mul, they're >>> used >>> for further initialization. >>> 3. if the corecfg_clockmultiplier is incorrect, sdhci will use improper >>> frequency to play. >>> >>> I think we don't need to store it due to it's a fixed value at run-time, >>> even if it is reset after a power cycle, the above will not be changed >>> via >>> software, except for dirver unbind . >>> >>>> I know that: >>>> >>>> 1. If I don't pick this patch and I suspend/resume, >>>> corecfg_clockmultiplier and corecfg_baseclkfreq are still fine after >>>> suspend / resume. >>>> >>>> 2. If I do pick this patch and I suspend/resume, >>>> corecfg_clockmultiplier and corecfg_baseclkfreq are wrong after >>>> suspend/resume (tested by reading /dev/mem directly from userspace >>>> after suspend/resume). >>>> >>>> >>>> Are you saying that it is unimportant that corecfg_clockmultiplier and >>>> corecfg_baseclkfreq are wrong? >>> >>> >>> Yup, corecfg_* stuff will be reset after a power cycle. >>> I mean that we need only to guarantee they're correct at probe time. >> >> So are you saying that the entire purpose of "corecfg_clockmultiplier" >> is that causes the "ClockMultiplier" field of the "EMMCCORE_CAP" >> register to get a certain value? >> ...and that the entire purpose of "corecfg_baseclkfreq" is that it >> causes the "BaseClockFreqSDClock" field of the "EMMCCORE_CAP" register >> to get a certain value? > > Yes, on rk3399: > corecfg_clockmultiplier <===> EMMCCORE_CAP1[23:16] ClockMultiplier > corecfg_baseclkfreq <===> EMMCCORE_CAP[15:8] BaseClockFreqSDClock > > If you re-write to either corecfg_* stuff, the corresponding CAP register > field will be changed too. > sdhci driver will fetch CAP register for initialization, we only need to > guarantee they're correct at probe time. > > Did that all make sense? Yes. Very odd, but it makes sense. It would still be nice to get these restored after runtime resume just for cleanliness, but it's not a blocker IMHO. Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
