Hi Ulf, On 2016/11/25 21:06, Ulf Hansson wrote: > [...] > >>>>>>> + >>>>>>> + /* >>>>>>> + * Xenon Specific property: >>>>>>> + * emmc: explicitly indicate whether this slot is for eMMC >>>>>>> + * slotno: the index of slot. Refer to SDHC_SYS_CFG_INFO register >>>>>>> + * tun-count: the interval between re-tuning >>>>>>> + * PHY type: "sdhc phy", "emmc phy 5.0" or "emmc phy 5.1" >>>>>>> + */ >>>>>>> + if (of_property_read_bool(np, "marvell,xenon-emmc")) >>>>>>> + priv->emmc_slot = true; >>>>>> >>>>>> So, you need this because of the eMMC voltage switch behaviour, right? >>>>>> >>>>>> Then I would rather like to describe this a generic DT bindings for >>>>>> the eMMC voltage level support. There have acutally been some earlier >>>>>> discussions for this, but we haven't yet made some changes. >>>>>> >>>>>> I think what is missing is a mmc-ddr-3_3v DT binding, which when set, >>>>>> allows the host driver to accept I/O voltage switches to 3.3V. If not >>>>>> supported the ->start_signal_voltage_switch() ops may return -EINVAL. >>>>>> This would inform the mmc core to move on to the next supported >>>>>> voltage level. There might be some minor additional changes to the mmc >>>>>> card initialization sequence, but those should be simple. >>>>>> >>>>>> I can help out to look into this, unless you want to do it yourself of course!? >>>>>> >>>>> Yes. One of the reasons is to provide eMMC specific voltage setting. >>>>> But in my very own opinion, it should be irrelevant to voltage level. >>>>> The eMMC voltage setting on our SDHC is different from SD/SDIO voltage switch. >>>>> It will become more complex with different SOC implementation details. >>>> >>>> Got it. Although I think we can cope with that fine just by using the >>>> different SD/eMMC speed modes settings defined in DT (or from the >>>> SDHCI caps register) >>>> >>> In my very opinion, I'm not sure if there is any corner case that driver cannot >>> determine the eMMC card type from DT and SDHC caps. >>> >>>>> Unfortunately, MMC driver cannot determine the card type yet when eMMC voltage >>>>> setting should be executed. >>>>> Thus an flag is required here to tell driver to execute eMMC voltage setting. >>>>> >>>>> Besides, additional eMMC specific settings might be implemented in future, besides >>>>> voltage setting. Most of them should be completed before MMC driver recognizes the >>>>> card type. Thus I have to keep this flag to indicate current SDHC is for eMMC. >>>> >>>> I doubt you will need a generic "eMMC" flag, but let's see when we go forward. >>>> >>>> Currently it's clear you don't need such a flag, so I will submit a >>>> change adding a DT binding for "mmc-ddr-3_3v" then we can take it from >>>> there, to see if it suits your needs. >>>> >> >> Another reason for a special "xenon-emmc" property is that our host IP usually can >> support both eMMC and SD. Whether a host is used as eMMC or SD depends on the >> final implementation of the actual product. >> Thus our host driver needs to know whether current SDHC is fixed as eMMC or SD. >> So far, It can only get the information from DT. > > As a matter of fact for mounted non-removable cards, such as eMMC, we > already have the option to describe some of their characteristics in > DT. Perhaps that's what you need? > > Please have a look at: > Documentation/devicetree/bindings/mmc/mmc-card.txt > Great! I will try this mmc-card sub-node. Thank you very much. Best regards, Hu Ziji >> >> After out host driver get the card type information from DT, it can prepare eMMC >> specific voltage, set eMMC specific mmc->caps/caps2 flags and do other >> vendor specific init, before card init procedure. >> Otherwise, our host driver has to wait until card type is determined in mmc_rescan(). >> >> A generic "eMMC" flag is unnecessary. I just require a private property, >> which is only used in our host driver and DT. >> >> Thank you. >> >> Best regards, >> Hu Ziji >> >>> >>> Actually, our eMMC is usually fixed as 1.8V. >>> >>> The pair "no-sd" + "no-sdio" can provide the similar information. >>> But I'm not sure if it is proper to use those two property in such a way. >>> >>> Thank you. >>> >>> Best regards >>> Hu Ziji >>> >>>> [...] >>>> >>>> Kind regards >>>> Uffe >>>> >>> -- >>> 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 >>> > > Kind regards > Uffe > -- 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
