Shawn, On Mon, Jun 13, 2016 at 5:59 PM, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote: >> Even in the case that an SoC designer didn't put a value into >> corecfg_baseclkfreq that matched register[15:8], it seems very likely >> that the rate returned from the clk_get_rate() would match. >> >> I guess what I'm saying is that, to me, it seems like my patch isn't >> broken in any real systems. If we ever find a system that needs this >> behavior in the future, we can add it. Until then, it seems like my >> patch would be fine. Do you agree? > > > I agree. But from the code itself, we should still use > SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN to see if we could get > it from internal register in case of some platforms don't > provide the clk stuff.. Sounds sane? :) Could we wait until there exists a SoC that needs to provide baseclkfreq in its sdhci_arasan_soc_ctl_map table and that needs this value copied from register[15:8]? AKA: A) If you have a SoC where clk_get_rate() is right and software needs to set baseclkfreq manualy, then you should include "baseclkfreq" in your sdhci_arasan_soc_ctl_map table. This is like rk3399. Note that if _both_ clk_get_rate() and register[15:8] are right, that's fine. We can still use clk_get_rate() since it will be exactly the same as register[15:8]. B) If you have a SoC that doesn't even expose corecfg_baseclkfreq to software control, just don't include "baseclkfreq" in your sdhci_arasan_soc_ctl_map table. Easy. This is how my patch treats anyone using the current "generic" bindings, but you could easily just specify an offset of "-1" for baseclkfreq if you didn't want to use the generic bindings but couldn't control baseclkfreq. C) If you have a SoC that provides a valid value in register[15:8] and clk_get_rate() is wrong and software is required to copy the value from register[15:8] to baseclkfreq, technically we should fix clk_get_rate() anyway. It's good when common clock framework provides correct values. NOTE: It seems very unlikely to me that register[15:8] would be right AND that software would be required to copy this value to baseclkfreq, but I suppose there are some pretty crazy hardware designs out there. D) If you have a SoC that provides a valid value in register[15:8] and clk_get_rate() is wrong and can't be fixed (REALLY?) and software is required to copy the value from register[15:8] to baseclkfreq, we will need to add new code. My assertion is that such a SoC doesn't exist and is unlikely to ever exist, so I am hesitant to add extra code to support this SoC. With my patch, A) and B) are certainly handled. I think C) is unlikely to exist, but if it did exist then I'd say we should fix clk_get_rate(). I think D) is VERY unlikely to exist. If I'm shown proof of D) existing, I'm happy to submit a patch for it. Until we see proof of D)'s existence, I don't think we should clutter the code with support for it. -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
